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  • 1. Adam, B.
    et al.
    Klawonn, I.
    Svedén, J.
    Bergkvist, J.
    Nahar, N.
    Walve, J.
    Littmann, S.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Lavik, G.
    Kuypers, M.M.M.
    Ploug, H.
    N2-fixation, ammonium release, and N-transfer to the microbial and classical food web within a plankton community.2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 19, p. 450-459Article in journal (Refereed)
    Abstract [en]

    We investigated the role of N2-fixation by the colony-forming cyanobacterium, Aphanizomenon spp., for the plankton community and N-budget of the N-limited Baltic Sea during summer by using stable isotope tracers combined with novel secondary ion mass spectrometry, conventional mass spectrometry and nutrient analysis. When incubated with 15N2, Aphanizomenon spp. showed a strong 15N-enrichment implying substantial 15N2-fixation. Intriguingly, Aphanizomenon did not assimilate tracers of 15NH4+ from the surrounding water. These findings are in line with model calculations that confirmed a negligible N-source by diffusion-limited NH4+ fluxes to Aphanizomenon colonies at low bulk concentrations (<250 nm) as compared with N2-fixation within colonies. No N2-fixation was detected in autotrophic microorganisms <5 μm, which relied on NH4+ uptake from the surrounding water. Aphanizomenon released about 50% of its newly fixed N2 as NH4+. However, NH4+ did not accumulate in the water but was transferred to heterotrophic and autotrophic microorganisms as well as to diatoms (Chaetoceros sp.) and copepods with a turnover time of ~5 h. We provide direct quantitative evidence that colony-forming Aphanizomenon releases about half of its recently fixed N2 as NH4+, which is transferred to the prokaryotic and eukaryotic plankton forming the basis of the food web in the plankton community. Transfer of newly fixed nitrogen to diatoms and copepods furthermore implies a fast export to shallow sediments via fast-sinking fecal pellets and aggregates. Hence, N2-fixing colony-forming cyanobacteria can have profound impact on ecosystem productivity and biogeochemical processes at shorter time scales (hours to days) than previously thought.

  • 2. Adam, Birgit
    et al.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Svedén, Jenny B.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bergkvist, Johanna
    Nahar, Nurun
    Walve, Jakob
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Littmann, Sten
    Whitehouse, Martin J.
    Lavik, Gaute
    Kuypers, Marcel M. M.
    Ploug, Helle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    N2-fixation, ammonium release and N-transfer to the microbial and classical food web within a plankton community2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 2, p. 450-459Article in journal (Refereed)
    Abstract [en]

    We investigated the role of N2-fixation by the colony-forming cyanobacterium, Aphanizomenon spp., for the plankton community and N-budget of the N-limited Baltic Sea during summer by using stable isotope tracers combined with novel secondary ion mass spectrometry, conventional mass spectrometry and nutrient analysis. When incubated with 15N2Aphanizomenon spp. showed a strong 15N-enrichment implying substantial 15N2-fixation. Intriguingly, Aphanizomenon did not assimilate tracers of 15NH4+ from the surrounding water. These findings are in line with model calculations that confirmed a negligible N-source by diffusion-limited NH4+ fluxes to Aphanizomenon colonies at low bulk concentrations (<250 nm) as compared with N2-fixation within colonies. No N2-fixation was detected in autotrophic microorganisms <5 μm, which relied on NH4+uptake from the surrounding water. Aphanizomenon released about 50% of its newly fixed N2 as NH4+. However, NH4+ did not accumulate in the water but was transferred to heterotrophic and autotrophic microorganisms as well as to diatoms (Chaetoceros sp.) and copepods with a turnover time of ~5 h. We provide direct quantitative evidence that colony-formingAphanizomenon releases about half of its recently fixed N2 as NH4+, which is transferred to the prokaryotic and eukaryotic plankton forming the basis of the food web in the plankton community. Transfer of newly fixed nitrogen to diatoms and copepods furthermore implies a fast export to shallow sediments via fast-sinking fecal pellets and aggregates. Hence, N2-fixing colony-forming cyanobacteria can have profound impact on ecosystem productivity and biogeochemical processes at shorter time scales (hours to days) than previously thought.

  • 3.
    Alvarez, Laura
    et al.
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Aliashkevich, Alena
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    de Pedro, Miguel A.
    Cava, Felipe
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Bacterial secretion of D-arginine controls environmental microbial biodiversity2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 2, p. 438-450Article in journal (Refereed)
    Abstract [en]

    Bacteria face tough competition in polymicrobial communities. To persist in a specific niche, many species produce toxic extracellular effectors to interfere with the growth of nearby microbes. These effectors include the recently reported non-canonical D-amino acids (NCDAAs). In Vibrio cholerae, the causative agent of cholera, NCDAAs control cell wall integrity in stationary phase. Here, an analysis of the composition of the extracellular medium of V. cholerae revealed the unprecedented presence of D-Arg. Compared with other D-amino acids, D-Arg displayed higher potency and broader toxicity in terms of the number of bacterial species affected. Tolerance to D-Arg was associated with mutations in the phosphate transport and chaperone systems, whereas D-Met lethality was suppressed by mutations in cell wall determinants. These observations suggest that NCDAAs target different cellular processes. Finally, even though virtually all Vibrio species are tolerant to D-Arg, only a few can produce this D-amino acid. Indeed, we demonstrate that D-Arg may function as part of a cooperative strategy in vibrio communities to protect non-producing members from competing bacteria. Because NCDAA production is widespread in bacteria, we anticipate that D-Arg is a relevant modulator of microbial subpopulations in diverse ecosystems.

  • 4.
    Anderson, Jennifer L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nieuwenhuis, Bart P. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Division of Evolutionary Biology, Faculty of Biology, Ludwig- Maximilians-Universität München.
    Johannesson, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
    Asexual reproduction and growth rate: independent and plastic lifehistory traits in Neurospora crassa2019In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 13, no 3, p. 780-788Article in journal (Refereed)
  • 5. Andersson, Anders F.
    et al.
    Riemann, Lasse
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Bertilsson, Stefan
    Pyrosequencing reveals contrasting seasonal dynamics of taxa within Baltic Sea bacterioplankton communities2010In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, l, Vol. 4, p. 171-181Article in journal (Refereed)
    Abstract [en]

    Variation in traits causes bacterial populations to respond in contrasting ways to environmental drivers. Learning about this will help us understand the ecology of individual populations in complex ecosystems. We used 454 pyrosequencing of the hypervariable region V6 of the 16S rRNA gene to study seasonal dynamics in Baltic Sea bacterioplankton communities, and link community and population changes to biological and chemical factors. Surface samples were collected from May to October 2003 and in May 2004 at the Landsort Deep in the central Baltic Sea Proper. The analysis rendered, on average, 20 200 sequence reads for each of the eight samples analyzed, providing the first detailed description of Baltic Sea bacterial communities. Community composition varied dramatically over time, supporting the idea of strong temporal shifts in bacterioplankton assemblages, and clustered according to season (including two May samples from consecutive years), suggesting repeatable seasonal succession. Overall, community change was most highly correlated with change in phosphorus concentration and temperature. Individual bacterial populations were also identified that tightly co-varied with different Cyanobacteria populations. Comparing the abundance profiles of operational taxonomic units at different phylogenetic distances revealed a weak but significant negative correlation between abundance profile similarity and genetic distance, potentially reflecting habitat filtering of evolutionarily conserved functional traits in the studied bacterioplankton.

  • 6.
    Bahram, Mohammad
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology. Univ Tartu, Inst Ecol & Earth Sci, 40 Lai St, EE-50411 Tartu, Estonia.
    Kohout, Petr
    Anslan, Sten
    Harend, Helery
    Abarenkov, Kessy
    Tedersoo, Leho
    Stochastic distribution of small soil eukaryotes resulting from high dispersal and drift in a local environment2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, p. 885-896Article in journal (Refereed)
    Abstract [en]

    A central challenge in ecology is to understand the relative importance of processes that shape diversity patterns. Compared with aboveground biota, little is known about spatial patterns and processes in soil organisms. Here we examine the spatial structure of communities of small soil eukaryotes to elucidate the underlying stochastic and deterministic processes in the absence of environmental gradients at a local scale. Specifically, we focus on the fine-scale spatial autocorrelation of prominent taxonomic and functional groups of eukaryotic microbes. We collected 123 soil samples in a nested design at distances ranging from 0.01 to 64 m from three boreal forest sites and used 454 pyrosequencing analysis of Internal Transcribed Spacer for detecting Operational Taxonomic Units of major eukaryotic groups simultaneously. Among the main taxonomic groups, we found significant but weak spatial variability only in the communities of Fungi and Rhizaria. Within Fungi, ectomycorrhizas and pathogens exhibited stronger spatial structure compared with saprotrophs and corresponded to vegetation. For the groups with significant spatial structure, autocorrelation occurred at a very fine scale (<2 m). Both dispersal limitation and environmental selection had a weak effect on communities as reflected in negative or null deviation of communities, which was also supported by multivariate analysis, that is, environment, spatial processes and their shared effects explained on average <10% of variance. Taken together, these results indicate a random distribution of soil eukaryotes with respect to space and environment in the absence of environmental gradients at the local scale, reflecting the dominant role of drift and homogenizing dispersal.

  • 7.
    Baltar, Federico
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Arístegui, Javier
    Gasol, Josep M.
    Lekunberri, Itziar
    Herndl, Gerhard J.
    Mesoscale eddies: hot-spots for prokaryotic diversity and function in the ocean2010In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 4, p. 975-988Article in journal (Refereed)
    Abstract [en]

    To investigate the effects of mesoscale eddies on prokaryotic assemblage structure and activity, we sampled two cyclonic eddies (CEs) and two anticyclonic eddies (AEs) in the permanent eddy-field downstream the Canary Islands. The eddy stations were compared with two far-field (FF) stations located also in the Canary Current, but outside the influence of the eddy field. The distribution of prokaryotic abundance (PA), bulk prokaryotic heterotrophic activity (PHA), various indicators of single-cell activity (such as nucleic acid content, proportion of live cells, and fraction of cells actively incorporating leucine), as well as bacterial and archaeal community structure were determined from the surface to 2000 m depth. In the upper epipelagic layer (0–200 m), the effect of eddies on the prokaryotic community was more apparent, as indicated by the higher PA, PHA, fraction of living cells, and percentage of active cells incorporating leucine within eddies than at FF stations. Prokaryotic community composition differed also between eddy and FF stations in the epipelagic layer. In the mesopelagic layer (200–1000 m), there were also significant differences in PA and PHA between eddy and FF stations, although in general, there were no clear differences in community composition or single-cell activity. The effects on prokaryotic activity and community structure were stronger in AE than CE, decreasing with depth in both types of eddies. Overall, both types of eddies show distinct community compositions (as compared with FF in the epipelagic), and represent oceanic ‘hotspots’ of prokaryotic activity (in the epi- and mesopelagic realms).

  • 8.
    Baltar, Federico
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. University of Otago, New Zealand.
    Palovaara, Joakim
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Wageningen University, The Netherlands.
    Unrein, Fernando
    Institut de Ciències del Mar CSIC, Spain.
    Catala, Philippe
    Pierre-and-Marie-Curie University, France.
    Hornak, Karel
    Biology Centre of the Academy of Sciences of the Czech Republic, Czech Republic.
    Simek, Karel
    Biology Centre of the Academy of Sciences of the Czech Republic, Czech Republic.
    Vaque, Dolors
    Institut de Ciències del Mar CSIC, Spain.
    Massana, Ramon
    Institut de Ciències del Mar CSIC, Spain.
    Gasol, Josep M.
    Institut de Ciències del Mar CSIC, Spain.
    Pinhassi, Jarone
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Marine bacterial community structure resilience to changes in protist predation under phytoplankton bloom conditions2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 3, p. 568-581Article in journal (Refereed)
    Abstract [en]

    To test whether protist grazing selectively affects the composition of aquatic bacterial communities, we combined high-throughput sequencing to determine bacterial community composition with analyses of grazing rates, protist and bacterial abundances and bacterial cell sizes and physiological states in a mesocosm experiment in which nutrients were added to stimulate a phytoplankton bloom. A large variability was observed in the abundances of bacteria (from 0.7 to 2.4 x 10(6) cells per ml), heterotrophic nanoflagellates (from 0.063 to 2.7 x 10(4) cells per ml) and ciliates (from 100 to 3000 cells per l) during the experiment (similar to 3-, 45- and 30-fold, respectively), as well as in bulk grazing rates (from 1 to 13 x 10(6) bacteria per ml per day) and bacterial production (from 3 to 379 mu g per Cl per day) (1 and 2 orders of magnitude, respectively). However, these strong changes in predation pressure did not induce comparable responses in bacterial community composition, indicating that bacterial community structure was resilient to changes in protist predation pressure. Overall, our results indicate that peaks in protist predation (at least those associated with phytoplankton blooms) do not necessarily trigger substantial changes in the composition of coastal marine bacterioplankton communities.

  • 9. Bendall, Matthew L
    et al.
    Stevens, Sarah LR
    Chan, Leong-Keat
    Malfatti, Stephanie
    Schwientek, Patrick
    Tremblay, Julien
    Schackwitz, Wendy
    Martin, Joel
    Pati, Amrita
    Bushnell, Brian
    Froula, Jeff
    Kang, Dongwan
    Tringe, Susannah G
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Moran, Mary A
    Shade, Ashley
    Newton, Ryan J
    McMahon, Katherine D
    Malmstrom, Rex R
    Genome-wide selective sweeps and gene-specific sweeps in natural bacterial populations2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 7, p. 1589-1601Article in journal (Refereed)
    Abstract [en]

    Multiple models describe the formation and evolution of distinct microbial phylogenetic groups. These evolutionary models make different predictions regarding how adaptive alleles spread through populations and how genetic diversity is maintained. Processes predicted by competing evolutionary models, for example, genome-wide selective sweeps vs gene-specific sweeps, could be captured in natural populations using time-series metagenomics if the approach were applied over a sufficiently long time frame. Direct observations of either process would help resolve how distinct microbial groups evolve. Here, from a 9-year metagenomic study of a freshwater lake (2005-2013), we explore changes in single-nucleotide polymorphism (SNP) frequencies and patterns of gene gain and loss in 30 bacterial populations. SNP analyses revealed substantial genetic heterogeneity within these populations, although the degree of heterogeneity varied by >1000-fold among populations. SNP allele frequencies also changed dramatically over time within some populations. Interestingly, nearly all SNP variants were slowly purged over several years from one population of green sulfur bacteria, while at the same time multiple genes either swept through or were lost from this population. These patterns were consistent with a genome-wide selective sweep in progress, a process predicted by the /`ecotype model/' of speciation but not previously observed in nature. In contrast, other populations contained large, SNP-free genomic regions that appear to have swept independently through the populations prior to the study without purging diversity elsewhere in the genome. Evidence for both genome-wide and gene-specific sweeps suggests that different models of bacterial speciation may apply to different populations coexisting in the same environment.

  • 10.
    Berg, Carlo
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Science for Life Laboratory (SciLifeLab). Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Germany.
    Vandieken, Verona
    Thamdrup, Bo
    Juergens, Klaus
    Significance of archaeal nitrification in hypoxic waters of the Baltic Sea2015In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 9, no 6, p. 1319-1332Article in journal (Refereed)
    Abstract [en]

    Ammonia-oxidizing archaea (AOA) of the phylum Thaumarchaeota are widespread, and their abundance in many terrestrial and aquatic ecosystems suggests a prominent role in nitrification. AOA also occur in high numbers in oxygen-deficient marine environments, such as the pelagic redox gradients of the central Baltic Sea; however, data on archaeal nitrification rates are scarce and little is known about the factors, for example sulfide, that regulate nitrification in this system. In the present work, we assessed the contribution of AOA to ammonia oxidation rates in Baltic deep basins and elucidated the impact of sulfide on this process. Rate measurements with N-15-labeled ammonium, CO2 dark fixation measurements and quantification of AOA by catalyzed reporter deposition-fluorescence in situ hybridization revealed that among the three investigated sites the highest potential nitrification rates (122-884 nmol l(-1) per day) were measured within gradients of decreasing oxygen, where thaumarchaeotal abundance was maximal (2.5-6.9 x 10(5) cells per ml) and CO2 fixation elevated. In the presence of the archaeal-specific inhibitor GC7, nitrification was reduced by 86-100%, confirming the assumed dominance of AOA in this process. In samples spiked with sulfide at concentrations similar to those of in situ conditions, nitrification activity was inhibited but persisted at reduced rates. This result together with the substantial nitrification potential detected in sulfidic waters suggests the tolerance of AOA to periodic mixing of anoxic and sulfidic waters. It begs the question of whether the globally distributed Thaumarchaeota respond similarly in other stratified water columns or whether the observed robustness against sulfide is a specific feature of the thaumarchaeotal subcluster present in the Baltic Deeps.

  • 11.
    Bravo, Andrea Garcia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Zopfi, J
    Buck, Moritz
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Xu, J
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Schaefer, J. K.
    Poté, J.
    Cosio, C.
    Geobacteraceae are important members of mercury-methylating microbial communities of sediments impacted by wastewater releasesIn: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370Article in journal (Refereed)
  • 12.
    Bravo, Andrea Garcia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Zopfi, Jakob
    Aquatic and Stable Isotope Biogeochemistry, University of Basel, Basel CH-4056, Switzerland.
    Buck, Moritz
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Jingying, Xu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Schaefer, Jeffra K.
    Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
    Poté, John
    Environmental Biogeochemistry and Ecotoxicology, University of Geneva, Geneva CH-1205, Switzerland.
    Cosio, Claudia
    Environmental Biogeochemistry and Ecotoxicology, University of Geneva, Geneva CH-1205, Switzerland.;Unité Stress Environnementaux et BIOSurveillance des Milieux Aquatiques UMR-I 02 (SEBIO), Université de Reims Champagne Ardenne, Reims F-51687, France.
    Geobacteraceae are important members of mercury-methylating microbial communities of sediments impacted by waste water releases2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, p. 802-812Article in journal (Refereed)
    Abstract [en]

    Microbial mercury (Hg) methylation in sediments can result in bioaccumulation of the neurotoxin methylmercury (MMHg) in aquatic food webs. Recently, the discovery of the gene hgcA, required for Hg methylation, revealed that the diversity of Hg methylators is much broader than previously thought. However, little is known about the identity of Hg-methylating microbial organisms and the environmental factors controlling their activity and distribution in lakes. Here, we combined high-throughput sequencing of 16S rRNA and hgcA genes with the chemical characterization of sediments impacted by a waste water treatment plant that releases significant amounts of organic matter and iron. Our results highlight that the ferruginous geochemical conditions prevailing at 1–2 cm depth are conducive to MMHg formation and that the Hgmethylating guild is composed of iron and sulfur-transforming bacteria, syntrophs, and methanogens. Deltaproteobacteria, notably Geobacteraceae, dominated the hgcA carrying communities, while sulfate reducers constituted only a minor component, despite being considered the main Hg methylators in many anoxic aquatic environments. Because iron is widely applied in waste water treatment, the importance of Geobacteraceae for Hg methylation and the complexity of Hgmethylating communities reported here are likely to occur worldwide in sediments impacted by waste water treatment plant discharges and in iron-rich sediments in general.

  • 13.
    Comte, Jerome
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Can marine bacteria be recruited from freshwater sources and the air?2014In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 8, no 12, p. 2423-2430Article in journal (Refereed)
    Abstract [en]

    There is now clear evidence that microorganisms present biogeographic patterns, yet the processes that create and maintain them are still not well understood. In particular, the contribution of dispersal and its exact impact on local community composition is still unclear. For example, dispersing cells may not thrive in recipient environments, but may still remain part of the local species pool. Here, we experimentally tested if marine bacteria can be retrieved from freshwater communities (pelagic and sediment) and the atmosphere by exposing bacteria from three lakes, that differ in their proximity to the Norwegian Sea, to marine conditions. We found that the percentage of freshwater taxa decreased with increasing salinities, whereas marine taxa increased along the same gradient. Our results further showed that this increase was stronger for lake and sediment compared with air communities. Further, significant increases in the average niche breadth of taxa were found for all sources, and in particular lake water and sediment communities, at higher salinities. Our results therefore suggests that marine taxa can readily grow from freshwater sources, but that the response was likely driven by the growth of habitat generalists that are typically found in marine systems. Finally, there was a greater proportion of marine taxa found in communities originating from the lake closest to the Norwegian Sea. In summary, this study shows that the interplay between bacterial dispersal limitation and dispersal from internal and external sources may have an important role for community recovery in response to environmental change.

  • 14.
    Dzidic, Majda
    et al.
    Department of Health and Genomics, Center for Advanced Research in Public Health, Valencia, Spain.
    Collado, Maria C.
    Institute of Agrochemistry and Food Technology (IATA-CSIC), Department of Biotechnology, Unit of Lactic Acid Bacteria and Probiotics, Valencia, Spain.
    Abrahamsson, Thomas
    Department of Clinical and Experimental Medicine, Division of Pediatrics, Linköping University, Linköping, Sweden.
    Artacho, Alejandro
    Department of Health and Genomics, Center for Advanced Research in Public Health, Valencia, Spain.
    Stensson, Malin
    Jönköping University, School of Health and Welfare, HHJ, Dep. of Natural Science and Biomedicine. Jönköping University, School of Health and Welfare, HHJ. Oral health. Jönköping University, School of Health and Welfare, HHJ. CHILD. Jönköping University, School of Health and Welfare, HHJ. Biomedical Platform.
    Jenmalm, Maria C.
    Department of Clinical and Experimental Medicine, Division of Autoimmunity and Immune Regulation, Linköping University, Linköping, Sweden.
    Mira, Alex
    Department of Health and Genomics, Center for Advanced Research in Public Health, Valencia, Spain.
    Oral microbiome development during childhood: an ecological succession influenced by postnatal factors and associated with tooth decay2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 9, p. 2292-2306Article in journal (Refereed)
    Abstract [en]

    Information on how the oral microbiome develops during early childhood and how external factors influence this ecological process is scarce. We used high-throughput sequencing to characterize bacterial composition in saliva samples collected at 3, 6, 12, 24 months and 7 years of age in 90 longitudinally followed children, for whom clinical, dietary and health data were collected. Bacterial composition patterns changed through time, starting with “early colonizers”, including Streptococcus and Veillonella; other bacterial genera such as Neisseria settled after 1 or 2 years of age. Dental caries development was associated with diverging microbial composition through time. Streptococcus cristatus appeared to be associated with increased risk of developing tooth decay and its role as potential biomarker of the disease should be studied with species-specific probes. Infants born by C-section had initially skewed bacterial content compared with vaginally delivered infants, but this was recovered with age. Shorter breastfeeding habits and antibiotic treatment during the first 2 years of age were associated with a distinct bacterial composition at later age. The findings presented describe oral microbiota development as an ecological succession where altered colonization pattern during the first year of life may have long-term consequences for child's oral and systemic health. 

  • 15.
    Dzidic, Majda
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. CSISP FISABIO, Spain; Inst Agrochem and Food Technol IATA CSIC, Spain.
    Collado, Maria C.
    Inst Agrochem and Food Technol IATA CSIC, Spain.
    Abrahamsson, Thomas
    Linköping University, Department of Clinical and Experimental Medicine, Division of Children's and Women's health. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center of Paediatrics and Gynaecology and Obstetrics, H.K.H. Kronprinsessan Victorias barn- och ungdomssjukhus.
    Artacho, Alejandro
    CSISP FISABIO, Spain.
    Stensson, Malin
    Jonkoping Univ, Sweden.
    Jenmalm, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
    Mira, Alex
    CSISP FISABIO, Spain.
    Oral microbiome development during childhood: an ecological succession influenced by postnatal factors and associated with tooth decay2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 9, p. 2292-2306Article in journal (Refereed)
    Abstract [en]

    Information on how the oral microbiome develops during early childhood and how external factors influence this ecological process is scarce. We used high-throughput sequencing to characterize bacterial composition in saliva samples collected at 3, 6, 12, 24 months and 7 years of age in 90 longitudinally followed children, for whom clinical, dietary and health data were collected. Bacterial composition patterns changed through time, starting with "early colonizers", including Streptococcus and Veillonella; other bacterial genera such as Neisseria settled after 1 or 2 years of age. Dental caries development was associated with diverging microbial composition through time. Streptococcus cristatus appeared to be associated with increased risk of developing tooth decay and its role as potential biomarker of the disease should be studied with species-specific probes. Infants born by C-section had initially skewed bacterial content compared with vaginally delivered infants, but this was recovered with age. Shorter breastfeeding habits and antibiotic treatment during the first 2 years of age were associated with a distinct bacterial composition at later age. The findings presented describe oral microbiota development as an ecological succession where altered colonization pattern during the first year of life may have long-term consequences for childs oral and systemic health.

  • 16. Eichner, Meri J.
    et al.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wilson, Samuel T.
    Littmann, Sten
    Whitehouse, Martin J.
    Church, Matthew J.
    Kuypers, Marcel M. M.
    Karl, David M.
    Ploug, Helle
    Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO(2)2017In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 11, no 6, p. 1305-1317Article in journal (Refereed)
    Abstract [en]

    Gradients of oxygen (O-2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O-2 were investigated under different partial pressures of carbon dioxide (pCO(2)) in field-collected colonies of the marine dinitrogen (N-2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O-2, pH and CO2 concentrations over a day-night cycle. O-2 concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O-2 (up to similar to 200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15 nmol l(-1) proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O-2 fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO(2) levels, whereas N-2 fixation increased with increasing pCO(2). The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments.

  • 17. Eichner, M.J.
    et al.
    Klawonn, I.
    Wilson, S.T.
    Littmann, S.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Church, M.J.
    Kuypers, M.M.M.M.
    Karl, D.M.
    Ploug, H.
    Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO22017In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 11, p. 1305-1317Article in journal (Refereed)
    Abstract [en]

    Gradients of oxygen (O2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O2 were investigated under different partial pressures of carbon dioxide (pCO2) in field-collected colonies of the marine dinitrogen (N2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O2, pH and CO2concentrations over a day–night cycle. O2 concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O2 (up to ~200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15 nmol l−1 proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O2 fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO2 levels, whereas N2fixation increased with increasing pCO2. The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments.

  • 18.
    Eiler, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Mondav, Rhiannon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Sinclair, Lucas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Fernandez-Vidal, Leyden
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Scofield, Douglas G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Schwientek, Patrick
    Martinez-Garcia, Manuel
    Torrents, David
    McMahon, Katherine D.
    Andersson, Siv G. E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Stepanauskas, Ramunas
    Woyke, Tanja
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Tuning fresh: radiation through rewiring of central metabolism in streamlined bacteria2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 8, p. 1902-1914Article in journal (Refereed)
  • 19. Estrella Alcamán, María
    et al.
    Fernandez, Camila
    Delgado, Antonio
    Bergman, Birgitta
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Diez, Beatriz
    The cyanobacterium Mastigocladus fulfills the nitrogen demand of a terrestrial hot spring microbial mat2015In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 9, no 10, p. 2290-2303Article in journal (Refereed)
    Abstract [en]

    Cyanobacteria from Subsection V (Stigonematales) are important components of microbial mats in non-acidic terrestrial hot springs. Despite their diazotrophic nature (N-2 fixers), their impact on the nitrogen cycle in such extreme ecosystems remains unknown. Here, we surveyed the identity and activity of diazotrophic cyanobacteria in the neutral hot spring of Porcelana (Northern Patagonia, Chile) during 2009 and 2011-2013. We used 16S rRNA and the nifH gene to analyze the distribution and diversity of diazotrophic cyanobacteria. Our results demonstrate the dominance of the heterocystous genus Mastigocladus (Stigonematales) along the entire temperature gradient of the hot spring (69-38 degrees C). In situ nitrogenase activity (acetylene reduction), nitrogen fixation rates (cellular uptake of N-15(2)) and nifH transcription levels in the microbial mats showed that nitrogen fixation and nifH mRNA expression were light-dependent. Nitrogen fixation activities were detected at temperatures ranging from 58 degrees C to 46 degrees C, with maximum daily rates of 600 nmol C2H4 cm(-2) per day and 94.1 nmol N cm(-2) per day. These activity patterns strongly suggest a heterocystous cyanobacterial origin and reveal a correlation between nitrogenase activity and nifH gene expression during diurnal cycles in thermal microbial mats. N and C fixation in the mats contributed similar to 3 g Nm(-2) per year and 27 g Cm-2 per year, suggesting that these vital demands are fully met by the diazotrophic and photoautotrophic capacities of the cyanobacteria in the Porcelana hot spring.

  • 20. Farnelid, Hanna
    et al.
    Bentzon-Tilia, Mikkel
    Andersson, Anders F.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Jost, Guenter
    Labrenz, Matthias
    Juergens, Klaus
    Riemann, Lasse
    Active nitrogen-fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 7, p. 1413-1423Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea receives large nitrogen inputs by diazotrophic (N-2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N-2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N-2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 mu m size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 x 10(7) nifH copies l(-1). Abundant nifH transcripts (up to 3.2 x 10(4) transcripts l(-1)) within nifH cluster III and co-occurring N-2 fixation (0.44 +/- 0.26 nmol l(-1) day(-1)) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N-2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N-2 fixation could also be of importance in other suboxic regions of the world's oceans.

  • 21. Farnelid, Hanna
    et al.
    Bentzon-Tilia, Mikkel
    Andersson, Anders F.
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Bertilsson, Stefan
    Jost, Guenter
    Labrenz, Matthias
    Juergens, Klaus
    Riemann, Lasse
    Active nitrogen-fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 7, p. 1413-1423Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea receives large nitrogen inputs by diazotrophic (N-2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N-2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N-2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 mu m size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 x 10(7) nifH copies l(-1). Abundant nifH transcripts (up to 3.2 x 10(4) transcripts l(-1)) within nifH cluster III and co-occurring N-2 fixation (0.44 +/- 0.26 nmol l(-1) day(-1)) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N-2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N-2 fixation could also be of importance in other suboxic regions of the world's oceans.

  • 22.
    Farnelid, Hanna
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Bentzon-Tilia, Mikkel
    Andersson, Anders F.
    Bertilsson, Stefan
    Jost, Guenter
    Labrenz, Matthias
    Juergens, Klaus
    Riemann, Lasse
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Active nitrogen-fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 7, p. 1413-1423Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea receives large nitrogen inputs by diazotrophic (N-2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N-2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N-2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 mu m size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 x 10(7) nifH copies l(-1). Abundant nifH transcripts (up to 3.2 x 10(4) transcripts l(-1)) within nifH cluster III and co-occurring N-2 fixation (0.44 +/- 0.26 nmol l(-1) day(-1)) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N-2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N-2 fixation could also be of importance in other suboxic regions of the world's oceans.

  • 23.
    Farnelid, Hanna
    et al.
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Bentzon-Tilia, Mikkel
    Andersson, Anders F.
    Bertilsson, Stefan
    Jost, Guenter
    Labrenz, Matthias
    Juergens, Klaus
    Riemann, Lasse
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Active nitrogen-fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 7, p. 1413-1423Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea receives large nitrogen inputs by diazotrophic (N-2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N-2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N-2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 mu m size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 x 10(7) nifH copies l(-1). Abundant nifH transcripts (up to 3.2 x 10(4) transcripts l(-1)) within nifH cluster III and co-occurring N-2 fixation (0.44 +/- 0.26 nmol l(-1) day(-1)) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N-2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N-2 fixation could also be of importance in other suboxic regions of the world's oceans.

  • 24.
    Farnelid, Hanna
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Univ Calif Santa Cruz, USA.
    Turk-Kubo, Kendra
    Univ Calif Santa Cruz, USA.
    Ploug, Helle
    University of Gothenburg.
    Ossolinski, Justin E.
    Woods Hole Oceanog Inst, USA.
    Collins, James R.
    Woods Hole Oceanog Inst, USA;Univ Washington, USA.
    van Mooy, Benjamin A. S.
    Woods Hole Oceanog Inst, USA.
    Zehr, Jonathan P.
    Univ Calif Santa Cruz, USA.
    Diverse diazotrophs are present on sinking particles in the North Pacific Subtropical Gyre2019In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 13, no 1, p. 170-182Article in journal (Refereed)
    Abstract [en]

    Sinking particles transport carbon and nutrients from the surface ocean into the deep sea and are considered hot spots for bacterial diversity and activity. In the oligotrophic oceans, nitrogen (N-2)-fixing organisms (diazotrophs) are an important source of new N but the extent to which these organisms are present and exported on sinking particles is not well known. Sinking particles were collected every 6 h over a 2-day period using net traps deployed at 150 m in the North Pacific Subtropical Gyre. The bacterial community and composition of diazotrophs associated with individual and bulk sinking particles was assessed using 16S rRNA and nifH gene amplicon sequencing. The bacterial community composition in bulk particles remained remarkably consistent throughout time and space while large variations of individually picked particles were observed. This difference suggests that unique biogeochemical conditions within individual particles may offer distinct ecological niches for specialized bacterial taxa. Compared to surrounding seawater, particle samples were enriched in different size classes of globally significant N-2-fixing cyanobacteria including Trichodesmium, symbionts of diatoms, and the unicellular cyanobacteria Crocosphaera and UCYN-A. The particles also contained nifH gene sequences of diverse non-cyanobacterial diazotrophs suggesting that particles could be loci for N-2 fixation by heterotrophic bacteria. The results demonstrate that diverse diazotrophs were present on particles and that new N may thereby be directly exported from surface waters on sinking particles.

  • 25. Fernandez-Gomez, Beatriz
    et al.
    Richter, Michael
    Schueler, Margarete
    Pinhassi, Jarone
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Acinas, Silvia G.
    Gonzalez, Jose M.
    Pedros-Alio, Carlos
    Ecology of marine Bacteroidetes: a comparative genomics approach2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 5, p. 1026-1037Article in journal (Refereed)
    Abstract [en]

    Bacteroidetes are commonly assumed to be specialized in degrading high molecular weight (HMW) compounds and to have a preference for growth attached to particles, surfaces or algal cells. The first sequenced genomes of marine Bacteroidetes seemed to confirm this assumption. Many more genomes have been sequenced recently. Here, a comparative analysis of marine Bacteroidetes genomes revealed a life strategy different from those of other important phyla of marine bacterioplankton such as Cyanobacteria and Proteobacteria. Bacteroidetes have many adaptations to grow attached to particles, have the capacity to degrade polymers, including a large number of peptidases, glycoside hydrolases (GHs), glycosyl transferases, adhesion proteins, as well as the genes for gliding motility. Several of the polymer degradation genes are located in close association with genes for TonB-dependent receptors and transducers, suggesting an integrated regulation of adhesion and degradation of polymers. This confirmed the role of this abundant group of marine bacteria as degraders of particulate matter. Marine Bacteroidetes had a significantly larger number of proteases than GHs, while non-marine Bacteroidetes had equal numbers of both. Proteorhodopsin containing Bacteroidetes shared two characteristics: small genome size and a higher number of genes involved in CO2 fixation per Mb. The latter may be important in order to survive when floating freely in the illuminated, but nutrient-poor, ocean surface. The ISME Journal (2013) 7, 1026-1037; doi:10.1038/ismej.2012.169; published online 10 January 2013

  • 26. Fernández-Gómez, Beatriz
    et al.
    Díez, Beatriz
    Polz, Martin F.
    Ignacio Arroyo, José
    Alfaro, Fernando D.
    Marchandon, Germán
    Sanhueza, Cynthia
    Farías, Laura
    Trefault, Nicole
    Marquet, Pablo A.
    Molina-Montenegro, Marco A.
    Sylvander, Peter
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Snoeijs-Leijonmalm, Pauline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bacterial community structure in a sympagic habitat expanding with global warming: brackish ice brine at 85-90 degrees N2019In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 13, no 2, p. 316-333Article in journal (Refereed)
    Abstract [en]

    Larger volumes of sea ice have been thawing in the Central Arctic Ocean (CAO) during the last decades than during the past 800,000 years. Brackish brine (fed by meltwater inside the ice) is an expanding sympagic habitat in summer all over the CAO. We report for the first time the structure of bacterial communities in this brine. They are composed of psychrophilic extremophiles, many of them related to phylotypes known from Arctic and Antarctic regions. Community structure displayed strong habitat segregation between brackish ice brine (IB; salinity 2.4-9.6) and immediate sub-ice seawater (SW; salinity 33.3-34.9), expressed at all taxonomic levels (class to genus), by dominant phylotypes as well as by the rare biosphere, and with specialists dominating IB and generalists SW. The dominant phylotypes in IB were related to Candidatus Aquiluna and Flavobacterium, those in SW to Balneatrix and ZD0405, and those shared between the habitats to Halomonas, Polaribacter and Shewanella. A meta-analysis for the oligotrophic CAO showed a pattern with Flavobacteriia dominating in melt ponds, Flavobacteriia and Gammaproteobacteria in solid ice cores, Flavobacteriia, Gamma- and Betaproteobacteria, and Actinobacteria in brine, and Alphaproteobacteria in SW. Based on our results, we expect that the roles of Actinobacteria and Betaproteobacteria in the CAO will increase with global warming owing to the increased production of meltwater in summer. IB contained three times more phylotypes than SW and may act as an insurance reservoir for bacterial diversity that can act as a recruitment base when environmental conditions change.

  • 27.
    Fortunato, Caroline S.
    et al.
    University of Maryland Center for Environmental Science.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Herfort, Lydie
    Oregon Health & Sciences University.
    Needoba, Joseph A.
    Oregon Health & Sciences University.
    Peterson, Tawnya D.
    Oregon Health & Sciences University.
    Crump, Byron C.
    University of Maryland Center for Environmental Science.
    Determining indicator taxa across spatial and seasonal gradients in the Columbia River coastal margin2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 10, p. 1899-1911Article in journal (Refereed)
    Abstract [en]

    Bacterioplankton communities are deeply diverse and highly variable across space and time, but several recent studies demonstrate repeatable and predictable patterns in this diversity. We expanded on previous studies by determining patterns of variability in both individual taxa and bacterial communities across coastal environmental gradients. We surveyed bacterioplankton diversity across the Columbia River coastal margin, USA, using amplicon pyrosequencing of 16S rRNA genes from 596 water samples collected from 2007 to 2010. Our results showed seasonal shifts and annual reassembly of bacterioplankton communities in the freshwater-influenced Columbia River, estuary, and plume, and identified indicator taxa, including species from freshwater SAR11, Oceanospirillales, and Flavobacteria groups, that characterize the changing seasonal conditions in these environments. In the river and estuary, Actinobacteria and Betaproteobacteria indicator taxa correlated strongly with seasonal fluctuations in particulate organic carbon (ρ=−0.664) and residence time (ρ=0.512), respectively. In contrast, seasonal change in communities was not detected in the coastal ocean and varied more with the spatial variability of environmental factors including temperature and dissolved oxygen. Indicator taxa of coastal ocean environments included SAR406 and SUP05 taxa from the deep ocean, andProchlorococcus and SAR11 taxa from the upper water column. We found that in the Columbia River coastal margin, freshwater-influenced environments were consistent and predictable, whereas coastal ocean community variability was difficult to interpret due to complex physical conditions. This study moves beyond beta-diversity patterns to focus on the occurrence of specific taxa and lends insight into the potential ecological roles these taxa have in coastal ocean environments.

  • 28.
    Garcia, Sarahi L
    et al.
    Jena School for Microbial Communication (JSMC) and Microbial Ecology Group at Friedrich Schiller University Jena, Jena, Germany.
    McMahon, Katherine D
    Martinez-Garcia, Manuel
    Srivastava, Abhishek
    Sczyrba, Alexander
    Stepanauskas, Ramunas
    Grossart, Hans-Peter
    Woyke, Tanja
    Warnecke, Falk
    Metabolic potential of a single cell belonging to one of the most abundant lineages in freshwater bacterioplankton2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 1, p. 137-147Article in journal (Refereed)
    Abstract [en]

    Actinobacteria within the acI lineage are often numerically dominating in freshwater ecosystems, where they can account for >50% of total bacteria in the surface water. However, they remain uncultured to date. We thus set out to use single-cell genomics to gain insights into their genetic make-up, with the aim of learning about their physiology and ecological niche. A representative from the highly abundant acI-B1 group was selected for shotgun genomic sequencing. We obtained a draft genomic sequence in 75 larger contigs (sum=1.16 Mb), with an unusually low genomic G+C mol% (~42%). Actinobacteria core gene analysis suggests an almost complete genome recovery. We found that the acI-B1 cell had a small genome, with a rather low percentage of genes having no predicted functions (~15%) as compared with other cultured and genome-sequenced microbial species. Our metabolic reconstruction hints at a facultative aerobe microorganism with many transporters and enzymes for pentoses utilization (for example, xylose). We also found an actinorhodopsin gene that may contribute to energy conservation under unfavorable conditions. This project reveals the metabolic potential of a member of the global abundant freshwater Actinobacteria.

  • 29.
    Garcia, Sarahi L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab. University of Wisconsin-Madison, Madison, USA.
    Stevens, Sarah L R
    University of Wisconsin-Madison, Madison, USA.
    Crary, Benjamin
    University of Wisconsin-Madison, Madison, USA.
    Martinez-Garcia, Manuel
    University of Alicante, Alicante, Spain.
    Stepanauskas, Ramunas
    Bigelow Laboratory for Ocean Sciences, East Boothbay, USA.
    Woyke, Tanja
    DOE Joint Genome Institute, Walnut Creek, USA.
    Tringe, Susannah G
    DOE Joint Genome Institute, Walnut Creek, USA.
    Andersson, Siv G E
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Malmstrom, Rex R
    DOE Joint Genome Institute, Walnut Creek, USA.
    McMahon, Katherine D
    University of Wisconsin-Madison, Madison, USA.
    Contrasting patterns of genome-level diversity across distinct co-occurring bacterial populations2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 3, p. 742-755Article in journal (Refereed)
    Abstract [en]

    To understand the forces driving differentiation and diversification in wild bacterial populations, we must be able to delineate and track ecologically relevant units through space and time. Mapping metagenomic sequences to reference genomes derived from the same environment can reveal genetic heterogeneity within populations, and in some cases, be used to identify boundaries between genetically similar, but ecologically distinct, populations. Here we examine population-level heterogeneity within abundant and ubiquitous freshwater bacterial groups such as the acI Actinobacteria and LD12 Alphaproteobacteria (the freshwater sister clade to the marine SAR11) using 33 single-cell genomes and a 5-year metagenomic time series. The single-cell genomes grouped into 15 monophyletic clusters (termed "tribes") that share at least 97.9% 16S rRNA identity. Distinct populations were identified within most tribes based on the patterns of metagenomic read recruitments to single-cell genomes representing these tribes. Genetically distinct populations within tribes of the acI Actinobacterial lineage living in the same lake had different seasonal abundance patterns, suggesting these populations were also ecologically distinct. In contrast, sympatric LD12 populations were less genetically differentiated. This suggests that within one lake, some freshwater lineages harbor genetically discrete (but still closely related) and ecologically distinct populations, while other lineages are composed of less differentiated populations with overlapping niches. Our results point at an interplay of evolutionary and ecological forces acting on these communities that can be observed in real time.

  • 30. Ghylin, Trevor W
    et al.
    Garcia, Sarahi L
    Moya, Francisco
    Oyserman, Ben O
    Schwientek, Patrick
    Forest, Katrina T
    Mutschler, James
    Dwulit-Smith, Jeffrey
    Chan, Leong-Keat
    Martinez-Garcia, Manuel
    Sczyrba, Alexander
    Stepanauskas, Ramunas
    Grossart, Hans-Peter
    Woyke, Tanja
    Warnecke, Falk
    Malmstrom, Rex
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    McMahon, Katherine D
    Comparative single-cell genomics reveals potential ecological niches for the freshwater acI Actinobacteria lineage2014In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 8, no 12, p. 2503-2516Article in journal (Refereed)
    Abstract [en]

    Members of the acI lineage of Actinobacteria are the most abundant microorganisms in most freshwater lakes; however, our understanding of the keys to their success and their role in carbon and nutrient cycling in freshwater systems has been hampered by the lack of pure cultures and genomes. We obtained draft genome assemblies from 11 single cells representing three acI tribes (acI-A1, acI-A7, acI-B1) from four temperate lakes in the United States and Europe. Comparative analysis of acI SAGs and other available freshwater bacterial genomes showed that acI has more gene content directed toward carbohydrate acquisition as compared to Polynucleobacter and LD12 Alphaproteobacteria, which seem to specialize more on carboxylic acids. The acI genomes contain actinorhodopsin as well as some genes involved in anaplerotic carbon fixation indicating the capacity to supplement their known heterotrophic lifestyle. Genome-level differences between the acI-A and acI-B clades suggest specialization at the clade level for carbon substrate acquisition. Overall, the acI genomes appear to be highly streamlined versions of Actinobacteria that include some genes allowing it to take advantage of sunlight and N-rich organic compounds such as polyamines, di- and oligopeptides, branched-chain amino acids and cyanophycin. This work significantly expands the known metabolic potential of the cosmopolitan freshwater acI lineage and its ecological and genetic traits.

  • 31.
    Guy, Lionel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Spang, Anja
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Saw, Jimmy Hser Wah
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Ettema, Thijs J. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    'Geoarchaeote NAG1' is a deeply rooting lineage of the archaeal order Thermoproteales rather than a new phylum2014In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 8, no 7, p. 1353-1357Article in journal (Other academic)
  • 32.
    Howard-Varona, Cristina
    et al.
    University of Arizona, USA.
    Roux, Simon
    University of Arizona, USA.
    Dore, Hugo
    École normale supérieure de Lyon, France.
    Solonenko, Natalie E
    University of Arizona, USA.
    Holmfeldt, Karin
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Markillie, Lye M
    Pacific Northwest National Laboratory, USA.
    Orr, Galya
    Pacific Northwest National Laboratory, USA.
    Sullivan, Matthew B
    University of Arizona, USA.
    Regulation of infection efficiency in a globally abundant marine Bacteriodetes virus.2017In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 11, no 1, p. 284-295Article in journal (Refereed)
    Abstract [en]

    Bacteria impact humans, industry and nature, but do so under viral constraints. Problematically, knowledge of viral infection efficiencies and outcomes derives from few model systems that over-represent efficient lytic infections and under-represent virus-host natural diversity. Here we sought to understand infection efficiency regulation in an emerging environmental Bacteroidetes-virus model system with markedly different outcomes on two genetically and physiologically nearly identical host strains. For this, we quantified bacterial virus (phage) and host DNA, transcripts and phage particles throughout both infections. While phage transcriptomes were similar, transcriptional differences between hosts suggested host-derived regulation of infection efficiency. Specifically, the alternative host overexpressed DNA degradation genes and underexpressed translation genes, which seemingly targeted phage DNA particle production, as experiments revealed they were both significantly delayed (by >30 min) and reduced (by >50%) in the inefficient infection. This suggests phage failure to repress early alternative host expression and stress response allowed the host to respond against infection by delaying phage DNA replication and protein translation. Given that this phage type is ubiquitous and abundant in the global oceans and that variable viral infection efficiencies are central to dynamic ecosystems, these data provide a critically needed foundation for understanding and modeling viral infections in nature.

  • 33.
    Hubalek, Valerie
    et al.
    Uppsala University.
    Wu, Xiaofen
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Eiler, Alexander
    Uppsala University.
    Buck, Moritz
    Uppsala University.
    Heim, Christine
    Univ Göttingen, Germany.
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Bertilsson, Stefan
    Uppsala University.
    Ionescu, Danny
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Germany.
    Connectivity to the surface determines diversity patterns in subsurface aquifers of the Fennoscandian shield2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 10, p. 2447-2458Article in journal (Refereed)
    Abstract [en]

    Little research has been conducted on microbial diversity deep under the Earth's surface. In this study, the microbial communities of three deep terrestrial subsurface aquifers were investigated. Temporal community data over 6 years revealed that the phylogenetic structure and community dynamics were highly dependent on the degree of isolation from the earth surface biomes. The microbial community at the shallow site was the most dynamic and was dominated by the sulfur-oxidizing genera Sulfurovum or Sulfurimonas at all-time points. The microbial community in the meteoric water filled intermediate aquifer (water turnover approximately every 5 years) was less variable and was dominated by candidate phylum OD1. Metagenomic analysis of this water demonstrated the occurrence of key genes for nitrogen and carbon fixation, sulfate reduction, sulfide oxidation and fermentation. The deepest water mass (5000 year old waters) had the lowest taxon richness and surprisingly contained Cyanobacteria. The high relative abundance of phylogenetic groups associated with nitrogen and sulfur cycling, as well as fermentation implied that these processes were important in these systems. We conclude that the microbial community patterns appear to be shaped by the availability of energy and nutrient sources via connectivity to the surface or from deep geological processes.

  • 34.
    Hubalek, Valerie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wu, Xiaofen
    Linnaeus Univ, Ctr Ecol & Evolut Microbial Model Syst EEMiS, Kalmar, Sweden.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Buck, Moritz
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Heim, Christine
    Univ Gottingen, GZG Geobiol, Gottingen, Germany.
    Dopson, Mark
    Linnaeus Univ, Ctr Ecol & Evolut Microbial Model Syst EEMiS, Kalmar, Sweden.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Ionescu, Danny
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Expt Limnol, Neuglobsow, Germany.
    Connectivity to the surface determines diversity patterns in subsurface aquifers of the Fennoscandian shield2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 10, p. 2447-2458Article in journal (Refereed)
    Abstract [en]

    Little research has been conducted on microbial diversity deep under the Earth/'s surface. In this study, the microbial communities of three deep terrestrial subsurface aquifers were investigated. Temporal community data over 6 years revealed that the phylogenetic structure and community dynamics were highly dependent on the degree of isolation from the earth surface biomes. The microbial community at the shallow site was the most dynamic and was dominated by the sulfur-oxidizing genera Sulfurovum or Sulfurimonas at all-time points. The microbial community in the meteoric water filled intermediate aquifer (water turnover approximately every 5 years) was less variable and was dominated by candidate phylum OD1. Metagenomic analysis of this water demonstrated the occurrence of key genes for nitrogen and carbon fixation, sulfate reduction, sulfide oxidation and fermentation. The deepest water mass (5000 year old waters) had the lowest taxon richness and surprisingly contained Cyanobacteria. The high relative abundance of phylogenetic groups associated with nitrogen and sulfur cycling, as well as fermentation implied that these processes were important in these systems. We conclude that the microbial community patterns appear to be shaped by the availability of energy and nutrient sources via connectivity to the surface or from deep geological processes.

  • 35.
    Isabell, Klawonn
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ploug, Helle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Aerobic and anaerobic nitrogen transformation processes in N2-fixing cyanobacterial aggregates2015In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 9, no 1, p. 1456-1466Article in journal (Refereed)
    Abstract [en]

    Colonies of N2-fixing cyanobacteria are key players in supplying new nitrogen to the ocean, but the biological fate of this fixed nitrogen remains poorly constrained. Here, we report on aerobic and anaerobic microbial nitrogen transformation processes that co-occur within millimetre-sized cyanobacterial aggregates (Nodularia spumigena) collected in aerated surface waters in the Baltic Sea. Microelectrode profiles showed steep oxygen gradients inside the aggregates and the potential for nitrous oxide production in the aggregates’ anoxic centres. 15N-isotope labelling experiments and nutrient analyses revealed that N2 fixation, ammonification, nitrification, nitrate reduction to ammonium, denitrification and possibly anaerobic ammonium oxidation (anammox) can co-occur within these consortia. Thus, N. spumigena aggregates are potential sites of nitrogen gain, recycling and loss. Rates of nitrate reduction to ammonium and N2 were limited by low internal nitrification rates and low concentrations of nitrate in the ambient water. Presumably, patterns of N-transformation processes similar to those observed in this study arise also in other phytoplankton colonies, marine snow and fecal pellets. Anoxic microniches, as a pre-condition for anaerobic nitrogen transformations, may occur within large aggregates (1 mm) even when suspended in fully oxygenated waters, whereas anoxia in small aggregates (<1 to 0.1 mm) may only arise in low-oxygenated waters (25 μM). We propose that the net effect of aggregates on nitrogen loss is negligible in NO3-depleted, fully oxygenated (surface) waters. In NO3-enriched (>1.5 μM), O2-depleted water layers, for example, in the chemocline of the Baltic Sea or the oceanic mesopelagic zone, aggregates may promote N-recycling and -loss processes.

  • 36.
    Jernberg, Cecilia
    et al.
    Karolinska Institutet.
    Löfmark, Sonja
    Karolinska Institutet.
    Edlund, Charlotta
    Karolinska Institutet / Medical Products Agency.
    Jansson, Janet K.
    Swedish University of Agricultural Sciences.
    Long-term ecological impacts of antibiotic administration on the human intestinal microbiota2007In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 1, no 1, p. 56-66Article in journal (Refereed)
    Abstract [en]

    Antibiotic administration is known to cause short-term disturbances in the microbiota of the human gastrointestinal tract, but the potential long-term consequences have not been well studied. The aims of this study were to analyse the long-term impact of a 7-day clindamycin treatment on the faecal microbiota and to simultaneously monitor the ecological stability of the microbiota in a control group as a baseline for reference. Faecal samples from four clindamycin-exposed and four control subjects were collected at nine different time points over 2 years. Using a polyphasic approach, we observed highly significant disturbances in the bacterial community that persisted throughout the sampling period. In particular, a sharp decline in the clonal diversity of Bacteroides isolates, as assessed by repetitive sequence-based PCR (rep-PCR) and long-term persistence of highly resistant clones were found as a direct response to the antibiotic exposure. The Bacteroides community never returned to its original composition during the study period as assessed using the molecular fingerprinting technique, terminal restriction fragment length polymorphism (T-RFLP). Furthermore, using real-time PCR we found a dramatic and persistent increase in levels of specific resistance genes in DNA extracted from the faeces after clindamycin administration. The temporal variations in the microbiota of the control group were minor compared to the large and persistent shift seen in the exposed group. These results demonstrate that long after the selection pressure from a short antibiotic exposure has been removed, there are still persistent long term impacts on the human intestinal microbiota that remain for up to 2 years post-treatment.

  • 37.
    Klawonn, Isabell
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. GB-Leibniz-Institute ofFreshwater Ecology and Inland Fisheries, Germany.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Department of Geological Sciences.
    Whitehouse, Martin J.
    Littmann, Sten
    Tienken, Daniela
    Kuypers, Marcel M. M.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ploug, Helle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Untangling hidden nutrient dynamics: rapid ammonium cycling and single-cell ammonium assimilation in marine plankton communities2019In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 13, no 8, p. 1960-1974Article in journal (Refereed)
    Abstract [en]

    Ammonium is a central nutrient in aquatic systems. Yet, cell-specific ammonium assimilation among diverse functional plankton is poorly documented in field communities. Combining stable-isotope incubations (15N-ammonium, 15N2 and 13C-bicarbonate) with secondary-ion mass spectrometry, we quantified bulk ammonium dynamics, N2-fixation and carbon (C) fixation, as well as single-cell ammonium assimilation and C-fixation within plankton communities in nitrogen (N)-depleted surface waters during summer in the Baltic Sea. Ammonium production resulted from regenerated (≥91%) and new production (N2-fixation, ≤9%), supporting primary production by 78–97 and 2–16%, respectively. Ammonium was produced and consumed at balanced rates, and rapidly recycled within 1 h, as shown previously, facilitating an efficient ammonium transfer within plankton communities. N2-fixing cyanobacteria poorly assimilated ammonium, whereas heterotrophic bacteria and picocyanobacteria accounted for its highest consumption (~20 and ~20–40%, respectively). Surprisingly, ammonium assimilation and C-fixation were similarly fast for picocyanobacteria (non-N2-fixing Synechococcus) and large diatoms (Chaetoceros). Yet, the population biomass was high for Synechococcus but low for Chaetoceros. Hence, autotrophic picocyanobacteria and heterotrophic bacteria, with their high single-cell assimilation rates and dominating population biomass, competed for the same nutrient source and drove rapid ammonium dynamics in N-depleted marine waters.

  • 38.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercé
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
    Székely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Temporal variation of beta-diversity and assembly mechanisms in a bacterial metacommunity2012In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 6, no 6, p. 1107-1114Article in journal (Refereed)
    Abstract [en]

    The turnover of community composition across space, beta-diversity, is influenced by different assembly mechanisms, which place varying weight on local habitat factors, such as environmental conditions and species interactions, and regional factors such as dispersal and history. Several assembly mechanisms may function simultaneously; however, little is known about how their importance changes over time and why. Here, we implemented a field survey where we sampled a bacterial metacommunity consisting of 17 rock pools located at the Swedish Baltic Sea coast at 11 occasions during 1 year. We determined to which extent communities were structured by different assembly mechanisms using variation partitioning and studied changes in beta-diversity across environmental gradients over time. beta-Diversity was highest at times of high overall productivity and environmental heterogeneity in the metacommunity, at least partly due to species sorting, that is, selection of taxa by the prevailing environmental conditions. In contrast, dispersal-driven assembly mechanisms were primarily detected at times when beta-diversity was relatively low. There were no indications for strong and persistent differences in community composition or beta-diversity between permanent and temporary pools, indicating that the physical disturbance regime is of relatively minor importance. In summary, our study clearly suggests that there are temporal differences in the relative importance of different assembly mechanisms related to abiotic factors and shows that the temporal variability of those factors is important for a more complete understanding of bacterial metacommunity dynamics.

  • 39.
    Larsson, John
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Celepli, Narin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ininbergs, Karolina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dupont, Christopher L.
    Yooseph, Shibu
    Bergman, Bigitta
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ekman, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Picocyanobacteria containing a novel pigment gene cluster dominate the brackish water Baltic Sea2014In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 8, no 9, p. 1892-1903Article in journal (Refereed)
    Abstract [en]

    Photoautotrophic picocyanobacteria harvest light via phycobilisomes (PBS) consisting of the pigments phycocyanin (PC) and phycoerythrin (PE), encoded by genes in conserved gene clusters. The presence and arrangement of these gene clusters give picocyanobacteria characteristic light absorption properties and allow the colonization of specific ecological niches. To date, a full understanding of the evolution and distribution of the PBS gene cluster in picocyanobacteria has been hampered by the scarcity of genome sequences from fresh-and brackish water-adapted strains. To remediate this, we analysed genomes assembled from metagenomic samples collected along a natural salinity gradient, and over the course of a growth season, in the Baltic Sea. We found that while PBS gene clusters in picocyanobacteria sampled in marine habitats were highly similar to known references, brackish-adapted genotypes harboured a novel type not seen in previously sequenced genomes. Phylogenetic analyses showed that the novel gene cluster belonged to a clade of uncultivated picocyanobacteria that dominate the brackish Baltic Sea throughout the summer season, but are uncommon in other examined aquatic ecosystems. Further, our data suggest that the PE genes were lost in the ancestor of PC-containing coastal picocyanobacteria and that multiple horizontal gene transfer events have re-introduced PE genes into brackish-adapted strains, including the novel clade discovered here.

  • 40.
    Lind, Anders E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Lewis, William H
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Spang, Anja
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Guy, Lionel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Embley, T Martin
    Ettema, Thijs J. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Genomes of two archaeal endosymbionts show convergent adaptations to an intracellular lifestyle.2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 11, p. 2655-2667Article in journal (Refereed)
    Abstract [en]

    Endosymbiosis is a widespread phenomenon in the microbial world and can be based on diverse interactions between endosymbiont and host cell. The vast majority of the known endosymbiotic interactions involve bacteria that have invaded eukaryotic host cells. However, methanogenic archaea have been found to thrive in anaerobic, hydrogenosome-containing protists and it was suggested that this symbiosis is based on the transfer of hydrogen. Here, we used culture-independent genomics approaches to sequence the genomes of two distantly related methanogenic endosymbionts that have been acquired in two independent events by closely related anaerobic ciliate hosts Nyctotherus ovalis and Metopus contortus, respectively. The sequences obtained were then validated as originating from the ciliate endosymbionts by in situ probing experiments. Comparative analyses of these genomes and their closest free-living counterparts reveal that the genomes of both endosymbionts are in an early stage of adaptation towards endosymbiosis as evidenced by the large number of genes undergoing pseudogenization. For instance, the observed loss of genes involved in amino acid biosynthesis in both endosymbiont genomes indicates that the endosymbionts rely on their hosts for obtaining several essential nutrients. Furthermore, the endosymbionts appear to have gained significant amounts of genes of potentially secreted proteins, providing targets for future studies aiming to elucidate possible mechanisms underpinning host-interactions. Altogether, our results provide the first genomic insights into prokaryotic endosymbioses from the archaeal domain of life.

  • 41.
    Lind, Peter A
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Massey Univ Albany, New Zealand Inst Adv Study, Auckland, New Zealand; Massey Univ Albany, Allan Wilson Ctr Mol Ecol & Evolut, Auckland, New Zealand.
    Farr, Andrew D
    New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology and Evolution, Massey University.
    Rainey, Paul B
    New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology and Evolution, Massey University; Department of Microbial Population Biology, Max Planck Institute for Evolutionary Biology; Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris-Tech), PSL Research University.
    Evolutionary convergence in experimental Pseudomonas populations2017In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 11, no 3, p. 589-600Article in journal (Refereed)
    Abstract [en]

    Model microbial systems provide opportunity to understand the genetic bases of ecological traits, their evolution, regulation and fitness contributions. Experimental populations of Pseudomonas fluorescens rapidly diverge in spatially structured microcosms producing a range of surface-colonising forms. Despite divergent molecular routes, wrinkly spreader (WS) niche specialist types overproduce a cellulosic polymer allowing mat formation at the air–liquid interface and access to oxygen. Given the range of ways by which cells can form mats, such phenotypic parallelism is unexpected. We deleted the cellulose-encoding genes from the ancestral genotype and asked whether this mutant could converge on an alternate phenotypic solution. Two new traits were discovered. The first involved an exopolysaccharide encoded by pgaABCD that functions as cell–cell glue similar to cellulose. The second involved an activator of an amidase (nlpD) that when defective causes cell chaining. Both types form mats, but were less fit in competition with cellulose-based WS types. Surprisingly, diguanylate cyclases linked to cellulose overexpression underpinned evolution of poly-beta-1,6-N-acetyl-d-glucosamine (PGA)-based mats. This prompted genetic analyses of the relationships between the diguanylate cyclases WspR, AwsR and MwsR, and both cellulose and PGA. Our results suggest that c-di-GMP regulatory networks may have been shaped by evolution to accommodate loss and gain of exopolysaccharide modules facilitating adaptation to new environments.

  • 42.
    Logares, Ramiro
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg Brendan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Paterson, Harriet
    Laybourn-Parry, Johanna
    Rengefors, Karin
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Biogeography of bacterial communities exposed to progressive long-term environmental change2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 5, p. 937-948Article in journal (Refereed)
    Abstract [en]

    The response of microbial communities to long-term environmental change is poorly understood. Here, we study bacterioplankton communities in a unique system of coastal Antarctic lakes that were exposed to progressive long-term environmental change, using 454 pyrosequencing of the 16S rDNA gene (V3-V4 regions). At the time of formation, most of the studied lakes harbored marine-coastal microbial communities, as they were connected to the sea. During the past 20 000 years, most lakes isolated from the sea, and subsequently they experienced a gradual, but strong, salinity change that eventually developed into a gradient ranging from freshwater (salinity 0) to hypersaline (salinity 100). Our results indicated that present bacterioplankton community composition was strongly correlated with salinity and weakly correlated with geographical distance between lakes. A few abundant taxa were shared between some lakes and coastal marine communities. Nevertheless, lakes contained a large number of taxa that were not detected in the adjacent sea. Abundant and rare taxa within saline communities presented similar biogeography, suggesting that these groups have comparable environmental sensitivity. Habitat specialists and generalists were detected among abundant and rare taxa, with specialists being relatively more abundant at the extremes of the salinity gradient. Altogether, progressive long-term salinity change appears to have promoted the diversification of bacterioplankton communities by modifying the composition of ancestral communities and by allowing the establishment of new taxa. The ISME Journal (2013) 7, 937-948; doi:10.1038/ismej.2012.168; published online 20 December 2012

  • 43. Logue, Jurg B.
    et al.
    Stedmon, Colin A.
    Kellerman, Anne M.
    Nielsen, Nikoline J.
    Andersson, Anders F.
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Laudon, Hjalmar
    Lindstrom, Eva S.
    Kritzberg, Emma S.
    Experimental insights into the importance of aquatic bacterial community composition to the degradation of dissolved organic matter2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 3, p. 533-545Article in journal (Refereed)
    Abstract [en]

    Bacteria play a central role in the cycling of carbon, yet our understanding of the relationship between the taxonomic composition and the degradation of dissolved organic matter (DOM) is still poor. In this experimental study, we were able to demonstrate a direct link between community composition and ecosystem functioning in that differently structured aquatic bacterial communities differed in their degradation of terrestrially derived DOM. Although the same amount of carbon was processed, both the temporal pattern of degradation and the compounds degraded differed among communities. We, moreover, uncovered that low-molecular-weight carbon was available to all communities for utilisation, whereas the ability to degrade carbon of greater molecular weight was a trait less widely distributed. Finally, whereas the degradation of either low-or high-molecular-weight carbon was not restricted to a single phylogenetic clade, our results illustrate that bacterial taxa of similar phylogenetic classification differed substantially in their association with the degradation of DOM compounds. Applying techniques that capture the diversity and complexity of both bacterial communities and DOM, our study provides new insight into how the structure of bacterial communities may affect processes of biogeochemical significance.

  • 44.
    Logue, Jurg B.
    et al.
    Lund Univ, Dept Biol Aquat Ecol, Solvegatan 37, S-22362 Lund, Sweden.;Sci Life Lab, Solna, Sweden..
    Stedmon, Colin A.
    Tech Univ Denmark, Natl Inst Aquat Resources, Charlottenlund, Denmark..
    Kellerman, Anne M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Nielsen, Nikoline J.
    Univ Copenhagen, Dept Plant & Environm Sci, Copenhagen, Denmark..
    Andersson, Anders F.
    KTH Royal Inst Technol, Sch Biotechnol, Sci Life Lab, Div Gene Technol, Solna, Sweden..
    Laudon, Hjalmar
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, S-90183 Umea, Sweden..
    Lindstrom, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kritzberg, Emma S.
    Lund Univ, Dept Biol Aquat Ecol, Solvegatan 37, S-22362 Lund, Sweden..
    Experimental insights into the importance of aquatic bacterial community composition to the degradation of dissolved organic matter2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 3, p. 533-545Article in journal (Refereed)
    Abstract [en]

    Bacteria play a central role in the cycling of carbon, yet our understanding of the relationship between the taxonomic composition and the degradation of dissolved organic matter (DOM) is still poor. In this experimental study, we were able to demonstrate a direct link between community composition and ecosystem functioning in that differently structured aquatic bacterial communities differed in their degradation of terrestrially derived DOM. Although the same amount of carbon was processed, both the temporal pattern of degradation and the compounds degraded differed among communities. We, moreover, uncovered that low-molecular-weight carbon was available to all communities for utilisation, whereas the ability to degrade carbon of greater molecular weight was a trait less widely distributed. Finally, whereas the degradation of either low-or high-molecular-weight carbon was not restricted to a single phylogenetic clade, our results illustrate that bacterial taxa of similar phylogenetic classification differed substantially in their association with the degradation of DOM compounds. Applying techniques that capture the diversity and complexity of both bacterial communities and DOM, our study provides new insight into how the structure of bacterial communities may affect processes of biogeochemical significance.

  • 45.
    Martijn, Joran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Schulz, Frederik
    Zaremba-Niedzwiedzka, Katarzyna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Viklund, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Stepanauskas, Ramunas
    Andersson, Siv G E
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Horn, Matthias
    Guy, Lionel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Ettema, Thijs J G
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Single-cell genomics of a rare environmental alphaproteobacterium provides unique insights into Rickettsiaceae evolution2015In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 9, no 11, p. 2373-2385Article in journal (Refereed)
    Abstract [en]

    The bacterial family Rickettsiaceae includes a group of well-known etiological agents of many human and vertebrate diseases, including epidemic typhus-causing pathogen Rickettsia prowazekii. Owing to their medical relevance, rickettsiae have attracted a great deal of attention and their host-pathogen interactions have been thoroughly investigated. All known members display obligate intracellular lifestyles, and the best-studied genera, Rickettsia and Orientia, include species that are hosted by terrestrial arthropods. Their obligate intracellular lifestyle and host adaptation is reflected in the small size of their genomes, a general feature shared with all other families of the Rickettsiales. Yet, despite that the Rickettsiaceae and other Rickettsiales families have been extensively studied for decades, many details of the origin and evolution of their obligate host-association remain elusive. Here we report the discovery and single-cell sequencing of 'Candidatus Arcanobacter lacustris', a rare environmental alphaproteobacterium that was sampled from Damariscotta Lake that represents a deeply rooting sister lineage of the Rickettsiaceae. Intriguingly, phylogenomic and comparative analysis of the partial 'Candidatus Arcanobacter lacustris' genome revealed the presence chemotaxis genes and vertically inherited flagellar genes, a novelty in sequenced Rickettsiaceae, as well as several host-associated features. This finding suggests that the ancestor of the Rickettsiaceae might have had a facultative intracellular lifestyle. Our study underlines the efficacy of single-cell genomics for studying microbial diversity and evolution in general, and for rare microbial cells in particular.

  • 46. Massana, R.
    et al.
    Unrein, F.
    Rodriguez-Martinez, R.
    Forn, I.
    Lefort, T.
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Not, F.
    Grazing rates and functional diversity of uncultured heterotrophic flagellates2009In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 3, no 5, p. 588-596Article in journal (Refereed)
    Abstract [en]

    Aquatic assemblages of heterotrophic protists are very diverse and formed primarily by organisms that remain uncultured. Thus, a critical issue is assigning a functional role to this unknown biota. Here we measured grazing rates of uncultured protists in natural assemblages (detected by fluorescent in situ hybridization (FISH)), and investigated their prey preference over several bacterial tracers in short-term ingestion experiments. These included fluorescently labeled bacteria (FLB) and two strains of the Roseobacter lineage and the family Flavobacteriaceae, of various cell sizes, which were offered alive and detected by catalyzed reporter deposition-FISH after the ingestion. We obtained grazing rates of the globally distributed and uncultured marine stramenopiles groups 4 and 1 (MAST-4 and MAST-1C) flagellates. Using FLB, the grazing rate of MAST-4 was somewhat lower than whole community rates, consistent with its small size. MAST-4 preferred live bacteria, and clearance rates with these tracers were up to 2 nl per predator per h. On the other hand, grazing rates of MAST-1C differed strongly depending on the tracer prey used, and these differences could not be explained by cell viability. Highest rates were obtained using FLB whereas the flavobacteria strain was hardly ingested. Possible explanations would be that the small flavobacteria cells were outside the effective size range of edible prey, or that MAST-1C selects against this particular strain. Our original dual FISH protocol applied to grazing experiments reveals important functional differences between distinct uncultured protists and offers the possibility to disentangle the complexity of microbial food webs.

  • 47. Monteux, Sylvain
    et al.
    Weedon, James T.
    Blume-Werry, Gesche
    Gavazov, Konstantin
    Jassey, Vincent E. J.
    Johansson, Margareta
    Keuper, Frida
    Olid, Carolina
    Dorrepaal, Ellen
    Long-term in situ permafrost thaw effects on bacterial communities and potential aerobic respiration2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, p. 2129-2141Article in journal (Refereed)
    Abstract [en]

    The decomposition of large stocks of soil organic carbon in thawing permafrost might depend on more than climate change-induced temperature increases: indirect effects of thawing via altered bacterial community structure (BCS) or rooting patterns are largely unexplored. We used a 10-year in situ permafrost thaw experiment and aerobic incubations to investigate alterations in BCS and potential respiration at different depths, and the extent to which they are related with each other and with root density. Active layer and permafrost BCS strongly differed, and the BCS in formerly frozen soils (below the natural thawfront) converged under induced deep thaw to strongly resemble the active layer BCS, possibly as a result of colonization by overlying microorganisms. Overall, respiration rates decreased with depth and soils showed lower potential respiration when subjected to deeper thaw, which we attributed to gradual labile carbon pool depletion. Despite deeper rooting under induced deep thaw, root density measurements did not improve soil chemistry-based models of potential respiration. However, BCS explained an additional unique portion of variation in respiration, particularly when accounting for differences in organic matter content. Our results suggest that by measuring bacterial community composition, we can improve both our understanding and the modeling of the permafrost carbon feedback.

  • 48.
    Monteux, Sylvain
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Weedon, James T.
    Blume-Werry, Gesche
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gavazov, Konstantin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Federal Institute for Forest, Snow and Landscape Research WSL, Lausanne, Switzerland.
    Jassey, Vincent E. J.
    Johansson, Margareta
    Keuper, Frida
    Olid, Carolina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Long-term in situ permafrost thaw effects on bacterial communities and potential aerobic respiration2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 9, p. 2129-2141Article in journal (Refereed)
    Abstract [en]

    The decomposition of large stocks of soil organic carbon in thawing permafrost might depend on more than climate change-induced temperature increases: indirect effects of thawing via altered bacterial community structure (BCS) or rooting patterns are largely unexplored. We used a 10-year in situ permafrost thaw experiment and aerobic incubations to investigate alterations in BCS and potential respiration at different depths, and the extent to which they are related with each other and with root density. Active layer and permafrost BCS strongly differed, and the BCS in formerly frozen soils (below the natural thawfront) converged under induced deep thaw to strongly resemble the active layer BCS, possibly as a result of colonization by overlying microorganisms. Overall, respiration rates decreased with depth and soils showed lower potential respiration when subjected to deeper thaw, which we attributed to gradual labile carbon pool depletion. Despite deeper rooting under induced deep thaw, root density measurements did not improve soil chemistry-based models of potential respiration. However, BCS explained an additional unique portion of variation in respiration, particularly when accounting for differences in organic matter content. Our results suggest that by measuring bacterial community composition, we can improve both our understanding and the modeling of the permafrost carbon feedback.

  • 49. Mukherjee, Shinjini
    et al.
    Juottonen, Heli
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Siivonen, Pauli
    Quesada, Cosme Lloret
    Tuom, Pirjo
    Pulkkine, Pertti
    Yrjälä, Kim
    Spatial patterns of microbial diversity and activity in an aged creosote-contaminated site2014In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 8, no 11, p. 2131-2142Article in journal (Refereed)
    Abstract [en]

    Restoration of polluted sites via in situ bioremediation relies heavily on the indigenous microbes and their activities. Spatial heterogeneity of microbial populations, contaminants and soil chemical parameters on such sites is a major hurdle in optimizing and implementing an appropriate bioremediation regime. We performed a grid-based sampling of an aged creosote-contaminated site followed by geostatistical modelling to illustrate the spatial patterns of microbial diversity and activity and to relate these patterns to the distribution of pollutants. Spatial distribution of bacterial groups unveiled patterns of niche differentiation regulated by patchy distribution of pollutants and an east-to-west pH gradient at the studied site. Proteobacteria clearly dominated in the hot spots of creosote pollution, whereas the abundance of Actinobacteria, TM7 and Planctomycetes was considerably reduced from the hot spots. The pH preferences of proteobacterial groups dominating in pollution could be recognized by examining the order and family-level responses. Acidobacterial classes came across as generalists in hydrocarbon pollution whose spatial distribution seemed to be regulated solely by the pH gradient. Although the community evenness decreased in the heavily polluted zones, basal respiration and fluorescein diacetate hydrolysis rates were higher, indicating the adaptation of specific indigenous microbial populations to hydrocarbon pollution. Combining the information from the kriged maps of microbial and soil chemistry data provided a comprehensive understanding of the long-term impacts of creosote pollution on the subsurface microbial communities. This study also highlighted the prospect of interpreting taxa-specific spatial patterns and applying them as indicators or proxies for monitoring polluted sites.

  • 50.
    Peura, Sari
    et al.
    Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Nykanen, Hannu
    Univ Jyvaskyla, Dept Biol & Environm Sci, Jyvaskyla 40014, Finland.
    Tiirola, Marja
    Univ Jyvaskyla, Dept Biol & Environm Sci, Jyvaskyla 40014, Finland.
    Jones, Roger I.
    Univ Jyvaskyla, Dept Biol & Environm Sci, Jyvaskyla 40014, Finland.
    Distinct and diverse anaerobic bacterial communities in boreal lakes dominated by candidate division OD12012In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 6, no 9, p. 1640-1652Article in journal (Refereed)
    Abstract [en]

    Lakes have a central role in the carbon cycle of the boreal landscape. These systems typically stratify in summer and their hypolimnetic microbial communities influence burial of biogenic organic matter in sediments. The composition of bacterial communities in these suboxic habitats was studied by pyrosequencing of 16S rRNA amplicons from five lakes with variable dissolved organic carbon (DOC) concentrations. Bacterioplankton communities in the hypolimnetic waters were clearly different from the surface layer with candidate division OD1, Chlorobi and Bacteroidetes as dominant community members. Several operational taxonomic units (OTUs) affiliated with candidate division OD1 were abundant and consistently present in the suboxic hypolimnion in these boreal lakes. The overall representation of this group was positively correlated with DOC and methane concentrations. Network analysis of time-series data revealed contrasting temporal patterns but suggested similar ecological roles among the abundant OTUs affiliated with candidate division OD1. Together, stable isotope data and taxonomic classification point to methane oxidation and autotrophic denitrification as important processes in the suboxic zone of boreal lakes. Our data revealed that while hypolimnetic bacterial communities are less dynamic, they appear to be more diverse than communities from the oxic surface layer. An appreciable proportion of the hypolimnetic bacteria belong to poorly described phyla.

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