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  • 1. Alonso-Saez, L
    et al.
    Aristegui, J
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Gomez-Consarnau, Laura
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Gonzalez, JM
    Vaque, D
    Agusti, S
    Gasol, JM
    Bacterial assemblage structure and carbon metabolism along a productivity gradient in the NE Atlantic Ocean2007In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 46, p. 43-53Article in journal (Refereed)
  • 2.
    Andersson, Eva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Brunberg, Anna-Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Net autotrophy in an oligotrophic lake rich in dissolved organic carbon and with high benthic primary production2006In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 43, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Biomass and production of microbiota—primary producers as well as heterotrophic bacteria—were studied both in the pelagial and in the benthic habitat over 2 yr in the shallow oligotrophic Lake Eckarfjärden, Sweden. Both biomass and production of microbiota were concentrated in the benthic habitat. Despite a high dissolved organic carbon (DOC) concentration of about 25 mg C l–1 in the water, the total bacterial production was lower than the total primary production. Moreover, measurements of DOC concentrations in the in- and outflow, and CO2-saturation measurements, indicate that the system is net autotrophic. Generally, low-productive systems (<100 µg C l–1 d–1) tend to be net heterotrophic. In contrast, we found a low-productive (55 µg C l–1 d–1) but net autotrophic system, the conditions of which were largely influenced by benthic production. Many lakes in the world are shallow and may provide substantial benthic areas suitable for primary production. Hence, it is important to include this habitat when evaluating whether lakes are autotrophic or heterotrophic systems.

  • 3.
    Andersson, Martin G. I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Catalán, Núria
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. ICRA, Catalan Institute of Water Research, Girona, Spain.
    Rahman, Zeeshanur
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Applied Microbiology and Biotechnology Laboratory, Department of Botany, University of Delhi.
    Tranvik, Lars J.
    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.
    Effects of sterilization on dissolved organic carbon (DOC) composition and bacterial utilization of DOC from lakes2018In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 82, no 2, p. 199-208Article in journal (Refereed)
    Abstract [en]

    Sterilization of dissolved organic carbon (DOC) is an essential step in research on interactions between DOC and organisms, for example where the effect of different microbial communities on DOC is studied or vice versa. However, few studies have gone beyond acknowledging that sterilization of DOC influences its characteristics. Here, we aimed to provide further knowledge that enables scientists to better tailor their sterilization methods to their research question. To meet this aim, we conducted a sterilization experiment with DOC from 4 boreal lakes treated with 4 sterilization methods, i.e. 2 filtrations (0.2 µm, 0.1 µm) and 2 autoclaving approaches (single and double autoclaving with a single pH adjustment). Quantity and spectroscopic properties of DOC, before and after sterilization, were studied, and DOC was further tested as a substrate for bacterial growth. We found that the filtration methods better preserved the different DOC measures. In contrast, autoclaving caused major inconsistent shifts in both qualitative and quantitative measures of DOC, as well as an increase of the maximum abundance of bacteria in growth experiments. Nonetheless, there remains a trade-off between retaining the quality of DOC and achieving sterile conditions. Therefore, the sterilization method of choice should be guided by the scientific question at hand.

  • 4.
    Baltar, Federico
    et al.
    Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, Campus Universitario de Tafira,.
    Arístegui, Javier
    Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, Campus Universitario de Tafira,.
    Gasol, Josep M.
    Herndl, Gerhard J.
    Prokaryotic carbon utilization in the dark ocean: : growth efficiency, leucine-to-carbon conversion factors, and their relation2010In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 60, no 3, p. 227-232Article in journal (Refereed)
    Abstract [en]

    Experiments were conducted in the mesopelagic subtropical northeast Atlantic Ocean to determine the range of variability in the prokaryotic leucine-to-carbon conversion factor (CF), and prokaryotic growth efficiency (PGE). The way prokaryotic heterotrophic production (PHP) is calcu- lated directly influences PGE (variations of PGE between 1 and 31% were found for a single sample). The empirically obtained deep-water CFs showed a 7-fold variability (0.13 to 0.85 kg C mol–1 Leu), but were always lower than the theoretical CF of 1.55 kg C mol–1 Leu assuming no isotope dilution. Empirically determined CFs were highly correlated to PGE, suggesting that both parameters are rep- resentations of the same basic metabolic processes. Overall, the PGEs obtained in this study suggest that mesopelagic prokaryotic assemblages can sometimes be as important in carbon processing as their epipelagic counterparts.

     

  • 5.
    Baltar, Federico
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Arístegui, Javier
    Gasol, Josep M.
    Sintes, Eva
    van Aken, Hendrik M.
    Herndl, Gerhard J.
    High dissolved extracellular enzymatic activity in the deep Central Atlantic Ocean2010In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 58, no 3, p. 287-302Article in journal (Refereed)
    Abstract [en]

    The distribution of prokaryotic abundance (PA), prokaryotic heterotrophic production (PHP), and suspended particulate organic material (POM), as well as total and dissolved (operationally defined as passing through 0.2 mu m pore size filters) potential extracellular enzymatic activities (EEA; alpha- and beta-glucosidase [AGase and BGase], leucine aminopeptidase [LAPase], and alkaline phosphatase [APase]) were determined in the meso- and bathypelagic waters of the (sub)tropical Atlantic along an eastern zonal transatlantic transect and a western N-S transect. Significant differences between both transects were found for POM concentration but not for PA, PHP (except in the subsurface and oxygen minimum layer), and dissolved and total EEA. PHP decreased by 3 orders of magnitude from the lower euphotic zone to bathypelagic waters, while PA and cell-specific PHP decreased only by 1 and 2 orders of magnitude, respectively. The proportion of the dissolved to the total EEA was high in the dark ocean for all the enzymes, ranging from 54 to 100, 56 to 100, 65 to 100 and 57 to 97 % for AGase, BGase, LAPase and APase, respectively. The kinetic parameters (V-max, and K-m) of both the dissolved and total fractions of LAPase and APase were very similar throughout the water column, suggesting a similar origin for both dissolved and particulate EEA. Significant correlations of both dissolved and total EEA were found with prokaryotic metabolism and the POM pool. Based on the previous notion that the fraction of dissolved EEA is higher in particle-attached than in free-living microbes, our results suggest that microbial activity in the dark ocean occurs mainly on colloidal and particulate material. This is in agreement with recent genomic evidence. However, these colloidal and particulate materials are prone to disruption during the sampling process. Hence, more selective sampling techniques are needed to specifically collect these deep-water aggregates that probably represent hotspots of microbial activity in the deep ocean.

  • 6.
    Baltar, Federico
    et al.
    Univ Las Palmas Gran Canaria, Fac Ciencias Mar, Las Palmas Gran Canaria 35017, Spain.
    Arístegui, Javier
    Herndl, Gerhard J
    Gasol, Josep M
    Hernández-León, Santiago
    Strong coast-ocean and surface-depth gradients in prokaryotic assemblage structure and activity in a coastal transition zone region2007In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 50, no 1, p. 63-74Article in journal (Refereed)
    Abstract [en]

    The distribution of marine Crenarchaeota Group 1, marine Euryarchaeota Group II and some major groups of Bacteria (SAR 11, Roseobacter, Gammaproteobacteria and Bacteroidetes) was investigated in the North Atlantic water column (surface to 2000 m depth) along a transect from the coastal waters of the NW African upwelling to the offshore waters of the Canary Coastal Transition Zone (CTZ). Catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) was used to describe the prokaryotic assemblages. Bulk picoplankton abundance and leucine incorporation were determined. Pronounced changes in prokaryotic assemblage composition were observed from the coast to the open ocean and at the deep chlorophyll maximum (DCM) with decreasing bulk heterotrophic activity. All bacterial groups decreased in absolute abundances from the coast to the open ocean; both archaeal groups increased towards the open ocean. Prokaryotic abundance and activity decreased 2 and 3 orders of magnitude, respectively, from the surface to 2000 m. Prokaryotic growth rates were high in the mesopelagic zone (similar to 0.13 d(-)1), compared to other reports from the central North Atlantic. SARI 1 in total picoplankton abundance decreased from 42 % in the DCM to 4 % at 2000 m, while marine Crenarchaeota Group I increased from 1 % in the DCM to 39 % in the oxygen minimum layer. A clear influence of the different intermediate water masses was observed on the bulk heterotrophic picoplankton activity, with lower leucine incorporation rates corresponding to layers where patches of Antarctic Intermediate Water were detected. Coast-ocean and surface-depth gradients in bulk prokaryotic abundance and production and assemblage composition were comparable to changes observed in basin-scale studies, pinpointing the CTZs as regions of strong variability in microbial diversity and metabolism. 

  • 7.
    Bastviken, David
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Ejlertsson, Jörgen
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Tranvik, Lars
    2Department of Limnology, Uppsala University, Sweden.
    Similar bacterial growth on dissolved organic matter in anoxic and oxic lake water2001In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 24, no 1, p. 41-49Article in journal (Refereed)
    Abstract [en]

    Anoxic metabolism yields less energy per unit substrate utilized than oxic respiration. In addition, substrate availability is believed to be reduced under anoxic conditions since oxygenases cannot be used. Consequently, it is generally assumed that bacteria grow slower in anoxic environments than in oxic environments. The results of the present study challenge this view. We compared the growth of bacterial assemblages under carbon-limited conditions in lake water under anoxic and oxic conditions. Bioassay experiments were performed with water from 3 lakes differin9 in nutrient concentrations and organic matter content. Amon9 bacteria usin9 the same source of organic matter, median anoxic growth rates were 84 to 110% of oxic growth rates. The total biomass yield durin9 the experiments did not differ between anoxic and oxic treatments. We suggest that anoxic bacterial growth was regulated by substrate availability rather than by metabolic energy yield and that availability of organic matter under anoxic conditions was equal to or even greater than that in oxic treatments. This implies that anoxic decomposition rates may actually have been faster than oxic rates.

  • 8.
    Bergfur, Jenny
    et al.
    Linköping University, The Tema Institute, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Sundberg, Carina
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Leaf-litter-associated fungi and bacteria along temporal and environmental gradients in boreal streams2014In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 73, no 3, p. 225-234Article in journal (Refereed)
    Abstract [en]

    Aquatic fungi and bacteria have long been recognized as key drivers in ecosystem processes such as leaf litter decomposition. We examined fungal and bacterial communities on decaying alder Alnus glutinosa (L.) Gaertner leaves along a gradient of increasing agricultural land use and associated nutrient enrichment in 9 boreal streams during 4 separate seasons (fall 2003, spring 2005, fall 2005, and spring 2006). Denaturing gradient gel electrophoresis (DGGE) and quantitative polymerase chain reactions (qPCR) showed that agricultural land use had significant effects on both bacterial and fungal communities, and on the ratios of fungi to total microbes associated with decomposing leaf litter. Furthermore, landscape factors and fluvial geomorphology appeared to influence the community composition of fungi and bacteria. Seasonal effects were found for fungal community structure only, indicating a higher temperature sensitivity of fungi compared to bacteria.

  • 9.
    Berglund, Johnny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Jürgens, Klaus
    Bruchmüller, Iris
    Wedin, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Use of group-specific PCR primers for identification of chrysophytes by denaturing gradient gel electrophoresis2005In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, ISSN 0948-3055, Vol. 39, no 2, p. 171-182Article in journal (Refereed)
    Abstract [en]

    The chrysophytes Chrysophyceae and Synurophyceae are ecologically important groups of autotrophic, mixotrophic and heterotrophic flagellates. The smallest forms are difficult to identify by classical microscopy but have important functions both as primary producers and as consumers of bacteria in the aquatic food chain. Group-specific primers for amplification of the 18S small sub-unit rRNA gene were developed for analysis of chrysophyte diversity by denaturing gradient gel electrophoresis (DGGE). Two different primer pairs were tested. The first primer pair (EukC1-F–Chryso-R) primarily targeted Paraphysomonadaceae and Ochromonadales, which generally have heterotrophic or mixotrophic nutrition. The second primer pair (EukC2-F–Chryso-R) targeted both Chrysophyceae and Synurophyceae. The primer pairs were tested for PCR amplification of the 18S rRNA gene of 25 cultured chrysophyte species and 6 other closely related nanoplanktonic species. Both primer pairs performed well, since PCR products were obtained for the corresponding chrysophyte cultures. None of the non-chrysophyte species were amplified with these primers. PCR products of chrysophyte cultures could be separated by DGGE in a denaturing gradient from 40 to 60%. In order to test this PCR-DGGE system for natural planktonic systems, we used field samples from a brackish water area (Baltic Sea) and a freshwater lake. The most intense DGGE bands were excised, sequenced and compared to sequences in GenBank. All obtained sequences grouped within the chrysophytes. Thus, the method seems to be promising for examining chrysophyte diversity in planktonic systems.

  • 10. Bertilsson, Stefan
    et al.
    Stepanauskas, Ramonas
    Cuadros-Hansson, Rocio
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Graneli, Wilhelm
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Tranvik, Lars
    Photochemically induced changes in bioavailable carbon and nitrogen pools in a boreal watershed1999In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 19, no 1, p. 47-56Article in journal (Refereed)
    Abstract [en]

    In several recent studies, a net stimulation of bacterial growth has been demonstrated after exposing humic surface waters to solar radiation or artificial ultraviolet radiation. This stimulation has been attributed to a photochemical release of bioavailable carbon or nitrogen compounds (ammonium). In a synoptic experiment, we exposed 0.2 mu m filtered water from 12 different habitats in a river system, dominated by allochthonous carbon input, to mild artificial UV radiation. A significant photochemical release of carboxylic acids of low molecular weight occurred. Furthermore, the exposure increased carbon-limited bacterial yield on average by a factor of 1.7. No photochemical production of free ammonium could be detected, which was in accordance with the lack of effects of radiation on bacterial growth yield under nitrogen-limited conditions. We conclude that, in boreal systems dominated by allochthonous carbon input, photochemical production of bioavailable carbon rather than nitrogen compounds is likely to positively influence the total substrate pool available for bacterial utilization.

  • 11.
    Bertilsson, Stefan
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Stepanauskas, Ramunas
    Cuadros-Hansson, Rociao
    Granéli, Wilhelm
    Wikner, Johan
    Tranvik, Lars
    Photochemically induced changes in bioavailable carbon and nitrogen pools in a boreal watershed1999In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 19, p. 47-56Article in journal (Refereed)
  • 12. Blackburn, N.
    et al.
    Zweifel, Ulla Li
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Hagström, Åke
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Cycling of marine dissolved organic matter: II. A model analysis.1996In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 11, p. 79-90Article in journal (Refereed)
  • 13.
    Burgmer, Tanja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Reiss, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wickham, Stephen A.
    Hillebrand, Helmut
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of snail grazers and light on the benthic microbial food web in periphyton communities2010In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 61, no 2, p. 163-178Article in journal (Refereed)
    Abstract [en]

    Periphyton harbours a complex microbial food web with different trophic levels, but little is known about trophic interactions within this food web and its response to factors that potentially control the entire community. We used natural periphyton communities from Lake Erken (Sweden) in 2 experiments manipulating grazer presence. In addition to an ungrazed control, we included natural densities of either of 2 snail species (Theodoxus fluviatilis and Bithynia tentaculata) in order to test how generalist consumers affect different components of the periphyton. In the second experiment, we additionally manipulated light supply to alter the heterotroph-autotroph ratio in the periphyton and thus potentially the trophic interactions. In both experiments, grazer presence decreased algal biomass immediately and shifted the community composition from dominance of large filamentous forms to dominance of prostrate and motile unicellular species. Biomass of bacteria, heterotrophic nanoflagellates, ciliates and meiofauna also decreased with grazing, but with differentiated temporal dynamics and effect strength. In the ungrazed control, first heterotrophic protists and later meiofaunal biomass increased, indicating strong bottom-up and top-down propagation of trophic interactions in the microbial food web. High light increased the biomass of mixotrophic ciliates and nanoautotrophs but not total algal biomass. Grazer presence decreased algal richness in the second experiment, but increased evenness of the algal community under high light conditions. We conclude that grazer presence puts different pressure on the components of the periphyton, which are further linked by direct or indirect internal trophic processes.

  • 14.
    Davis, Stephen L.
    et al.
    Texas A&M Univ, USA.
    Roelke, Daniel L.
    Texas A&M Univ, USA.
    Brooks, Bryan W.
    Baylor Univ, USA.
    Lundgren, Veronica
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Texas A&M Univ, USA.
    Withrow, Frances
    Texas A&M Univ, USA.
    Scott, W. Casan
    Baylor Univ, USA.
    Rotifer-Prymnesium parvum interactions: role of lake bloom history on rotifer adaptation to toxins produced by P-parvum2015In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 75, no 1, p. 55-68Article in journal (Refereed)
    Abstract [en]

    Prymnesium parvum is a harmful algal bloom species present in many inland water bodies of the southcentral USA, but does not form fish-killing blooms in all of them. The present study tested the hypothesis that rotifer grazing of P. parvum might influence the incidence of blooms. Three-day in-lake experiments, which focused on the size fraction of zooplankton dominated by rotifers and natural phytoplankton assemblages inoculated with P. parvum, were conducted during the time of bloom development in 2 reservoirs of the southcentral USA: Lakes Somerville and Whitney, where the latter experiences P. parvum blooms and the former does not. Toxicity at a level lethal to fish was only occasionally observed during these experiments, so our experimental treatments are considered to be at a low-toxicity level. As a whole, rotifers in Lakes Somerville and Whitney selectively grazed P. parvum. Rotifers in Lake Somerville appeared to benefit from this selective grazing, while rotifers in Lake Whitney did not. The differences between rotifer communities from these lakes might be because rotifers from Lake Somerville historically have only been exposed to low levels of toxins produced by P. parvum and were able to develop resistance to these toxins, thus enabling them to persist and perhaps contribute to the suppression of blooms there. The opportunity for this type of microevolutionary adaptation may not occur in lakes where P. parvum blooms and waters reach high toxicity levels, such as those which have occurred historically in Lake Whitney.

  • 15. Degerman, Rickard
    et al.
    Dinasquet, Julie
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Riemann, Lasse
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    de Luna, Sara Sjostedt
    Andersson, Agneta
    Effect of resource availability on bacterial community responses to increased temperature2013In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 68, no 2, p. 131-142Article in journal (Refereed)
    Abstract [en]

    Climate change is predicted to cause higher temperatures and increased precipitation, resulting in increased inflow of nutrients to coastal waters in northern Europe. This has been assumed to increase the overall heterotrophy, including enhanced bacterial growth. However, the relative importance of temperature, resource availability and bacterial community composition for the bacterial growth response is poorly understood. In the present study, we investigated effects of increased temperature on bacterial growth in waters supplemented with different nutrient concentrations and inoculated with microbial communities from distinct seasonal periods. Seven experiments were performed in the northern Baltic Sea spanning an entire annual cycle. In each experiment, bacterioplankton were exposed to 2 temperature regimes (in situ and in situ + 4 degrees C) and 5 nutrient concentrations. Generally, elevated temperature and higher nutrient levels caused an increase in the bacterial growth rate and a shortening of the response time (lag phase). However, at the lowest nutrient concentration, bacterial growth was low at all tested temperatures, implying a stronger dependence on resource availability than on temperature for bacterial growth. Furthermore, data indicated that different bacterial assemblages had varying temperature responses and that community composition was strongly affected by the combination of high nutrient addition and high temperature. These results support the concern that climate change will promote heterotrophy in aquatic systems, where nutrient levels will increase considerably. In such environments, the bacterial community composition will change, their growth rates will increase, and their response time will be shortened compared to the present situation.

  • 16.
    Degerman, Rickard
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dinasquet, Julie
    Kalmar, Sweden.
    Riemann, Lasse
    Kalmar, Sweden; Helsingör, Denmark.
    de Luna, Sara Sjostedt
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effect of resource availability on bacterial community responses to increased temperature2013In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 68, no 2, p. 131-142Article in journal (Refereed)
    Abstract [en]

    Climate change is predicted to cause higher temperatures and increased precipitation, resulting in increased inflow of nutrients to coastal waters in northern Europe. This has been assumed to increase the overall heterotrophy, including enhanced bacterial growth. However, the relative importance of temperature, resource availability and bacterial community composition for the bacterial growth response is poorly understood. In the present study, we investigated effects of increased temperature on bacterial growth in waters supplemented with different nutrient concentrations and inoculated with microbial communities from distinct seasonal periods. Seven experiments were performed in the northern Baltic Sea spanning an entire annual cycle. In each experiment, bacterioplankton were exposed to 2 temperature regimes (in situ and in situ + 4 degrees C) and 5 nutrient concentrations. Generally, elevated temperature and higher nutrient levels caused an increase in the bacterial growth rate and a shortening of the response time (lag phase). However, at the lowest nutrient concentration, bacterial growth was low at all tested temperatures, implying a stronger dependence on resource availability than on temperature for bacterial growth. Furthermore, data indicated that different bacterial assemblages had varying temperature responses and that community composition was strongly affected by the combination of high nutrient addition and high temperature. These results support the concern that climate change will promote heterotrophy in aquatic systems, where nutrient levels will increase considerably. In such environments, the bacterial community composition will change, their growth rates will increase, and their response time will be shortened compared to the present situation.

  • 17.
    del Valle, Daniela A.
    et al.
    University of Hawaii, USA.
    Martínez-García, Sandra
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. University of Hawaii, USA.
    Sañudo-Wilhelmy, Sergio A.
    University of Southern California, USA.
    Kiene, Ronald P.
    University of South Alabama, USA ; Dauphin Island Sea Lab, USA.
    Karl, David M.
    University of Hawaii, USA.
    Methionine and dimethylsulfoniopropionate as sources of sulfur to the microbial community of the North Pacific Subtropical Gyre2015In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 75, no 2, p. 103-116Article in journal (Refereed)
    Abstract [en]

    Methionine (Met) and dimethylsulfoniopropionate (DMSP) are 2 important substrates that can serve as sources of sulfur and carbon to microbial communities in the sea. We studied the vertical and diel distributions and the assimilation rates of dissolved Met (dMet) and dissolved DMSP (dDMSP) into proteins of different microbial groups at Stn ALOHA, in the oligotrophic North Pacific Subtropical Gyre (NPSG). Concentrations of dMet never exceeded 50 pM and were at their daily minimum during the night-time (<0.17 pM). dMet assimilation into proteins accounted for <30% of the dMet lost from the dissolved pool, suggesting that other metabolic pathways were also important. Concentrations of dDMSP ranged from 0.35 to 1.0 nM in surface waters and did not present a distinguishable diel pattern. Cell-sorted Prochlorococcus, high nucleic acid (HNA), and low nucleic acid (LNA) non-pigmented bacteria showed a clear diel pattern for dMet and dDMSP assimilation, with higher rates during the night-time. Among the different groups, HNA bacteria had the highest per-cell assimilation rate for dMet and dDMSP, but when accounting for cell numbers in each group, the HNA and LNA bacterial group assimilation rates were comparable for both dDMSP and dMet. Integrated water column (0 to 125 m) dDMSP assimilation rates by the entire microbial assemblage were 1.7- To 5.3-fold faster than those for dMet, suggesting that dDMSP constitutes a more important source of sulfur than dMet to the microbial community of the NPSG during the time of our study.

  • 18. Engström-Öst, Jonna
    et al.
    Hogfors, Hedvig
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    El-Shehawy, Rehab
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    De Stasio, Bart
    Vehmaa, Anu
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Toxin-producing cyanobacterium Nodularia spumigena, potential competitors and grazers: testing mechanisms of reciprocal interactions2011In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 62, no 1, p. 39-48Article in journal (Refereed)
    Abstract [en]

    Interactions among toxic cyanobacteria, sympatric algae and planktivorous grazers are key processes governing plankton dynamics and cyanobacterial blooms. We studied interactions between the cyanobacterium Nodularia spumigena and microalgae (Rhodomonas salina and Tetraselmis suecica) as well as effects of zooplankton (copepod Eurytemora affinis) grazing on these interactions. N. spumigena was incubated without algae or with algae at different concentrations and with or without copepods. Following similar to 24 h incubation, we assayed changes in N. spumigena and algae abundance, concentration of intracellular (IC) and dissolved nodularin (toxin produced by N. spumigena) and quantity of Nodularia DNA in copepod guts (as a proxy for grazing pressure on the cyanobacterium). In the presence of algae, IC nodularin levels increased in a concentration-dependent manner; however, when copepods were present in the mixtures of algae and cyanobacterium, this increase was significantly less. The presence of T. suecica negatively affected the growth rate of N. spumigena, whereas the presence of the cyanobacterium strongly impeded growth of R. salina, but not of T. suecica. The IC nodularin quota correlated negatively with growth of R. salina, implicating the toxin's involvement in the observed growth suppression of the eukaryotic alga. Copepods actively ingested N. spumigena, even when the alternative food was plentiful, and neither N. spumigena quantity nor its toxin concentrations influenced copepod feeding rates and survival. These findings suggest complex allelopathic interactions between the autotrophs, whereas mesozooplankton grazers have an indirect negative effect on the nodularin concentrations by suppressing the competitors. These findings underscore the need to study ecologically important interactions among toxic cyanobacteria, sympatric algae and grazers, if we are to understand mechanisms regulating cyanobacterial blooms.

  • 19. Fandino, L.B.
    et al.
    Riemann, Lasse
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Steward, G.F.
    Azam, F.
    Population dynamics of Cytophaga-Flavobacteria during marine phytoplankton blooms analyzed by quantitative real-time PCR.2005In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 40, p. 251-257Article in journal (Refereed)
  • 20. Fandino, L.B.
    et al.
    Riemann, Lasse
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Steward, G.F.
    Long, R.A.
    Azam, F.
    Variations in bacterial community structure during a dinoflagellate bloom analyzed by DGGE and 16S rDNA sequencing2001In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 23, p. 119-130Article in journal (Refereed)
  • 21.
    Farnelid, Hanna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Tarangkoon, Woraporn
    Hansen, Gert
    Hansen, Per Juel
    Riemann, Lasse
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Putative N-2-fixing heterotrophic bacteria associated with dinoflagellate-Cyanobacteria consortia in the low-nitrogen Indian Ocean2010In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 61, no 2, p. 105-117Article in journal (Refereed)
    Abstract [en]

    Heterotrophic dinoflagellates bearing unicellular cyanobacterial symbionts are common within the order Dinophysiales. However, the ecological role of these symbionts is unclear. Due to the occurrence of such consortia in oceanic waters characterized by low nitrogen concentrations, we hypothesized that the symbionts fix gaseous nitrogen (N-2). Individual heterotrophic dinoflagellates containing cyanobacterial symbionts were isolated from the open Indian Ocean and off Western Australia, and characterized using light microscopy, transmission electron microscopy (TEM), and nitrogenase (nifH) gene amplification, cloning, and sequencing. Cyanobacteria, heterotrophic bacteria and eukaryotic algae were recognized as symbionts of the heterotrophic dinoflagellates. nifH gene sequences were obtained from 23 of 37 (62%) specimens of dinoflagellates (Ornithocercus spp. and Amphisolenia spp.). Interestingly, only 2 specimens contained cyanobacterial nifH sequences, while 21 specimens contained nifH genes related to heterotrophic bacteria. Of the 137 nifH sequences obtained 68% were most similar to Alpha-, Beta-, and Gammaproteobacteria, 8% clustered with anaerobic bacteria, and 5% were related to second alternative nitrogenases (anfH). Twelve sequences from 5 host cells formed a discrete cluster which may represent a not yet classified nifH cluster. Eight dinoflagellates contained only 1 type of nifH sequence (>99% sequence identity) but overall the putative N-2-fixing symbionts did not appear host specific and mixed assemblages were often found in single host cells. This study provides the first insights into the nifH diversity of dinoflagellate symbionts and suggests a symbiotic co-existence of non-diazotrophic cyanobacteria and N-2-fixing heterotrophic bacteria in heterotrophic dinoflagellates.

  • 22.
    Farnelid, Hanna
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Univ Calif Santa Cruz, Ocean Sci Dept, Santa Cruz, CA 95064 USA.
    Turk-Kubo, Kendra
    Univ Calif Santa Cruz, USA.
    del Carmen Munoz-Marin, Maria
    Univ Calif Santa Cruz, USA ; Univ Cordoba, Spain.
    Zehr, Jonathan P.
    Univ Calif Santa Cruz, USA.
    New insights into the ecology of the globally significant uncultured nitrogen-fixing symbiont UCYN-A2016In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 77, no 3, p. 125-138Article, review/survey (Refereed)
    Abstract [en]

    Cyanobacterial nitrogen-fixers (diazotrophs) play a key role in biogeochemical cycling of carbon and nitrogen in the ocean. In recent years, the unusual symbiotic diazotrophic cyanobacterium Atelocyanobacterium thalassa (UCYN-A) has been recognized as one of the major diazotrophs in the tropical and subtropical oceans. In this review, we summarize what is currently known about the geographic distribution of UCYN-A, as well as the environmental factors that govern its distribution. In addition, by compiling UCYN-A nifH sequences from the GenBank no. database as well as those from nifH gene amplicon next generation sequencing studies, we present an in-depth analysis of the distribution of defined UCYN-A sublineages (UCYN-A1, UCYN-A2 and UCYN-A3) and identify a novel sublineage, UCYN-A4, which may be significant in some environments. Each UCYN-A sublineage exhibited a remarkable global distribution pattern and several UCYN-A sublineages frequently co-occurred within the same sample, suggesting that if they represent different ecotypes they have overlapping niches. Recently, single cell visualization techniques using specific probes targeting UCYN-A1 and UCYN-A2 and their respective associated eukaryotic partner cells showed that the size of the consortia and the number of UCYN-A cells differed between these 2 sublineages. Combined, the results highlight that UCYN-A sublineages likely have different physiological requirements, which need to be accounted for in future studies. Furthermore, based on our increasing knowledge of the diversity of the UCYN-A lineage, we discuss some of the limitations of currently used cultivation-independent molecular techniques for the identification and quantification of UCYN-A.

  • 23.
    Frank, Alexander H.
    et al.
    Univ Vienna, Austria.
    Pontiller, Benjamin
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Univ Vienna, Austria.
    Herndl, Gerhard J.
    Univ Vienna, Austria ; Royal Netherlands Inst Sea Res, Netherlands.
    Reinthaler, Thomas
    Univ Vienna, Austria.
    Erythromycin and GC7 fail as domain-specific inhibitors for bacterial and archaeal activity in the open ocean2016In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 77, no 2, p. 99-110Article in journal (Refereed)
    Abstract [en]

    Domain-specific metabolic inhibitors are currently used to differentiate archaeal from bacterial activity. However, studies testing the specificity of these inhibitors are sparse or are based on cultured strains. We determined the inhibition specificity of erythromycin (EMY) and N1-guanyl-1,7-diaminoheptane (GC7) on bacterial and archaeal communities in the North Atlantic. EMY and GC7 are assumed to inhibit bacterial and archaeal activity, respectively. Heterotrophic prokaryotic activity was estimated via H-3-leucine incorporation on the cell-specific level using catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography (MICRO-CARD-FISH). In the water masses studied, the contribution of Thaumarchaeota to total picoplankton abundance ranged from 5 to 24% while Euryarchaeota contributed 2 to 6%; the relative abundance of Bacteria ranged from 29 to 48%. The addition of EMY and GC7 reduced the bulk leucine incorporation by similar to 77% and similar to 41%, respectively. Evaluation of the inhibition efficiency of EMY on a cell-specific level showed no difference between Archaea (76.0 +/- 14.2% [SD]) and Bacteria (78.2 +/- 9.5%). Similarly, the reduction of substrate uptake in GC7-treated samples was similar in Archaea (59.9 +/- 24%) and Bacteria (47.2 +/- 9.6%). Taken together, our results suggest that in complex open-ocean prokaryotic communities neither EMY nor GC7 is efficient as a domain-specific inhibitor.

  • 24.
    Garcia, Sarahi L.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Mixed cultures as model communities: hunting for ubiquitous microorganisms, their partners, and interactions2016In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 77, no 2, p. 79-85Article in journal (Refereed)
    Abstract [en]

    Even though thousands of microbial strains have now been successfully cultivated and described, these only represent a small fraction of global microbial diversity. Moreover, many of the ubiquitous and abundant environmental microorganisms still defy axenic cultivation. Here, I present mixed cultures as a powerful tool to cultivate and study ubiquitous but hard-to-cultivate microorganisms. A mixed culture is a subsample from a complex natural community that contains 2 or more microbial strains. When cultivated together with their metabolic partners, these ubiquitous microorganisms can mutually satisfy metabolic dependencies just as they do in the environment. By reducing the complexity while keeping some diversity, mixed cultures can then be used as model communities. Furthermore, by combining the relative simplicity of these model communities with molecular and bioinformatics tools, the complex natural interactions could be deciphered one model community at a time. Ultimately, mixed cultures can be used to generate a working hypothesis to explore the microbial ecology and genetic population structures of the unseen vast majority of microorganisms.

  • 25. Gasol, J. M.
    et al.
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Alonso-Saez, L.
    Ducklow, H.
    Herndl, G. J.
    Koblizek, M.
    Labrenz, M.
    Luo, Y.
    Moran, X. A. G.
    Reinthaler, T.
    Simon, M.
    Towards a better understanding of the microbial carbon flux in the sea2008In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 53, p. 21-38Article in journal (Refereed)
    Abstract [en]

    We now have a relatively good idea of how bulk microbial processes shape the cycling of organic matter and nutrients in the sea. The advent of the molecular biology era in microbial ecology has resulted in advanced knowledge about the diversity of marine microorganisms, suggesting that we might have reached a high level of understanding of carbon fluxes in the oceans. However, it is becoming increasingly clear that there are large gaps in the understanding of the role of bacteria in regulating carbon fluxes. These gaps may result from methodological as well as conceptual limitations. For example, should bacterial production be measured in the light? Can bacterial production conversion factors be predicted, and how are they affected by loss of tracers through respiration? Is it true that respiration is relatively constant compared to production? How can accurate measures of bacterial growth efficiency be obtained? In this paper, we discuss whether such questions could (or should) be addressed. Ongoing genome analyses are rapidly widening our understanding of possible metabolic pathways and cellular adaptations used by marine bacteria in their quest for resources and struggle for survival (e.g. utilization of light, acquisition of nutrients, predator avoidance, etc.). Further, analyses of the identity of bacteria using molecular markers (e.g. subgroups of Bacteria and Archaea) combined with activity tracers might bring knowledge to a higher level. Since bacterial growth (and thereby consumption of DOC and inorganic nutrients) is likely regulated differently in different bacteria, it will be critical to learn about the life strategies of the key bacterial species to achieve a comprehensive understanding of bacterial regulation of C fluxes. Finally, some processes known to occur in the microbial food web are hardly ever characterized and are not represented in current food web models. We discuss these issues and offer specific comments and advice for future research agendas.

  • 26. Gasol, Josep M.
    et al.
    Pinhassi, Jarone
    Alonso-Sáez, Laura
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ducklow, Hugh
    Herndl, Gerhard J.
    Koblizek, Michal
    Labrenz, Matthias
    Luo, Yawei
    Morán, Xosé Anxelu G.
    Reinthaler, Thomas
    Simon, Meinhard
    Towards a better understanding of microbial carbon flux in the sea2008In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 53, no 1, p. 21-38Article in journal (Refereed)
    Abstract [en]

    We now have a relatively good idea of how bulk microbial processes shape the cycling of organic matter and nutrients in the sea. The advent of the molecular biology era in microbial ecology has resulted in advanced knowledge about the diversity of marine microorganisms, suggesting that we might have reached a high level of understanding of carbon fluxes in the oceans. However, it is becoming increasingly clear that there are large gaps in the understanding of the role of bacteria in regulating carbon fluxes. These gaps may result from methodological as well as conceptual limitations. For example, should bacterial production be measured in the light? Can bacterial production conversion factors be predicted, and how are they affected by loss of tracers through respiration? Is it true that respiration is relatively constant compared to production? How can accurate measures of bacterial growth efficiency be obtained? In this paper, we discuss whether such questions could (or should) be addressed. Ongoing genome analyses are rapidly widening our understanding of possible metabolic pathways and cellular adaptations used by marine bacteria in their quest for resources and struggle for survival (e.g. utilization of light, acquisition of nutrients, predator avoidance, etc.). Further, analyses of the identity of bacteria using molecular markers (e.g. subgroups of Bacteria and Archaea) combined with activity tracers might bring knowledge to a higher level. Since bacterial growth (and thereby consumption of DOC and inorganic nutrients) is likely regulated differently in different bacteria, it will be critical to learn about the life strategies of the key bacterial species to achieve a comprehensive understanding of bacterial regulation of C fluxes. Finally, some processes known to occur in the microbial food web are hardly ever characterized and are not represented in current food web models. We discuss these issues and offer specific comments and advice for future research agendas.

  • 27. Grossart, H.-P.
    et al.
    Riemann, Lasse
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Azam, F.
    Bacterial motility in the sea and its ecological implications2001In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 25, p. 247-258Article in journal (Refereed)
  • 28.
    Hagström, Åke
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Azam, Farooq
    Univ Calif San Diego, USA.
    Berg, Carlo
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Zweifel, Ulla Li
    University of Gothenburg.
    Isolates as models to study bacterial ecophysiology and biogeochemistry2018In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 80, no 1, p. 15-27Article in journal (Refereed)
    Abstract [en]

    Here, we examine the use of bacterial isolates growing in artificial media or seawater as a means to investigate bacterial activity in the upper ocean. The discovery of a major role of bacteria in the ocean's carbon cycle owes greatly to the development of culture-independent assemblage-level approaches; however, this should not detract from the recognition of model isolates as representing the environmental microbiome. A long-established tool for culturing bacteria, in medicine and general microbiology, has been agar plates. In addition, a great variety of liquid substrates including seawater have been used to successfully identify and cultivate important bacteria such as Pelagibacter ubique. Yet, the discrepancy between microscopic counts and plate counts, the great plate count anomaly, has led to a biased perception of the limited relevance of isolated bacteria. Linking isolates to whole-genome sequencing, phylogenetic analysis and computational modeling will result in culturable model bacteria from different habitats. Our main message is that bacterial ecophysiology, particularly growth rates in seawater, and functionalities inferred through the identity, abundance and expression of specific genes could be mechanistically linked if more work is done to isolate, culture and study bacteria in pure cultures. When we rally behind a strategy aimed at culturing targeted phenotypes, we are not saying that culture independent studies of bacteria in the sea are not informative. We are suggesting that culturebased studies can help integrate the ecological and genomic views.

  • 29.
    Hagström, Åke
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Zweifel, Ulla Li
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Biogeographical diversity among marine bacterioplankton2000In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 21, p. 231-244Article in journal (Refereed)
  • 30.
    Hagström, Åke
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Zweifel, Ulla Li
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Marine bacterioplankton show bursts of rapid growth induced by substrate shifts2001In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 24, p. 109-115Article in journal (Refereed)
  • 31.
    Hamisi, Mariam
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, Thomas
    University of Dar es Salaam, Tanzania.
    Muruke, Masoud
    University of Dar es Salaam, Tanzania.
    Bergman, Birgitta
    Stockholm University, Faculty of Science, Department of Botany.
    Nitrogen fixation by epiphytic and epibenthic diazotrophs associated with seagrass meadows along the Tanzanian coast, Western Indian Ocean2009In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 57, p. 33-42Article in journal (Refereed)
    Abstract [en]

    Seasonal, diurnal, and age-dependent variations in nitrogen fixation (nitrogenase activity) by epiphytic diazotrophs colonizing the seagrasses Halodule uninervis, Cymodocea rotundata, Thalassodendron ciliatum, and Thalassia hemprichii, and by epibenthic diazotrophs associated with seagrass-vegetated and nonvegetated sediments, were estimated at 2 sites along the Tanzanian coast, Western Indian Ocean. Acetylene reduction-gas chromatography showed that nitrogenase activity values were significantly higher (p = 0.0004) at the site with low nutrient levels (Mjimwema) than at the site with higher nutrient levels (Ocean Road). The nitrogenase activity ranged from 10 to 192 nmol N g–1 h–1 for H. uninervis, 7 to 80 nmol N g–1 h–1 for C. rotundata, 10 to 75 nmol N g–1 h–1 for Thalassia hemprichii, and from 4 to 61 nmol N g–1 h–1 for Thalassodendron ciliatum. Nitrogenase activity values in sediments covered by seagrasses were significantly higher than in surrounding nonvegetated sediments (t = 4.021, p = 0.0005). Significant variations in nitrogenase activity were apparent depending on leaf age and season, with highest activity being found in mid-aged leaves during the northeastern monsoon (NEM), and in older leaves during the southeastern monsoon (SEM). Daytime nitrogenase activity was appreciable on above-ground seagrass parts, while rhizosphere activity peaked at night-time. Collectively our data show that diazotrophs (cyanobacteria and other bacteria) are associated with seagrasses (leaves and roots), and potentially constitute an integral part of the ecosystem. They show highly dynamic nitrogenase activity and a succession in seagrass colonization, and we concluded that their presence may contribute to the productivity of the seagrass beds.

  • 32.
    Heinrich, Friederike
    et al.
    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.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Seasonality and environmental control of freshwater SAR11 (LD12) in a temperate lake (Lake Erken, Sweden)2013In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 70, no 1, p. 33-44Article in journal (Refereed)
    Abstract [en]

    THE SAR11 clade is ubiquitous and abundant in planktonic environments. In freshwater lakes, the clade is represented by tribe LD12 which is phylogenetically distinct from the marine SAR11. We studied the ecology of LD12 in a temperate dimictic lake (Lake Erken, Sweden), by analyzing its seasonal dynamics with quantitative PCR, CARD-FISH and 454 pyrosequencing of the 16S rRNA gene. Results showed that LD12 can be as numerous in freshwater bacterioplankton as their marine SAR11 siblings. They exhibited strong seasonality and made up from 1.8 to 40% of the total bacterial 16S rRNA pool (mean 14%) with pronounced peaks in summer and late fall. Except in spring, LD12 was the dominant Alphaproteobacteria, contributing on average 72% of the 16S rRNA within this class. The LD12 population was dominated by a single persistent ribotype, suggesting low local divergence, at least at the phylogenetic resolution accessed with rRNA genes. The relative abundance of LD12 was positively correlated to nutrient concentrations (phosphate, ammonia, nitrate, and silica) and water transparency whereas the relative abundance was lower during periods characterized by high phytoplankton biomass. Based on these observations we propose that LD12 are poor competitors during periods of high phytoplankton productivity and associated release of labile organic compounds, but thrive when availability of inorganic nutrients is high. Similar to the marine SAR11 sibling group, local LD12 populations appear to respond in contrasting ways to nutrient availability in different lakes, pointing to either ecological divergence within the tribe or variations in the interplay between environmental driver variables.

  • 33. Herndl, Gerhard J.
    et al.
    Agogué, Helene
    Baltar, Federico
    Royal Netherlands Inst Sea Res, Dept Biol Oceanog, NL-1790 AB Den Burg, Netherlands.
    Reinthaler, Thomas
    Sintes, Eva
    Varela, Marta M.
    Regulation of aquatic microbial processes: the ‘microbial loop’ of the sunlit surface waters and the dark ocean dissected2008In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 53, no Sp. Iss. 1, p. 59-68Article in journal (Refereed)
    Abstract [en]

    Our understanding of microbial food web interactions in the ocean is essentially based on research performed in the euphotic layer, where the interactions between phytoplankton and prokaryotic plankton, mainly heterotrophic Bacteria, are well established. In the euphotic layer, particularly in meso- and eutrophic waters, prokaryotic plankton are mainly top-down controlled by bacterivorous flagellates and viruses, affecting metabolically active, fast growing populations more than dormant stages. In the meso- and bathypelagic realm of the ocean, however, prokaryotic plankton are thought to be mainly bottom-up controlled, because the heterotrophic component of the prokaryotic community is limited by the availability of organic carbon. However, deep-water prokaryotes exhibit a number of peculiarities compared to prokaryotes in the euphotic layer, among which are a large genome size and a gene repertoire indicative of a predominately surface-attached mode of life. This indicates that deep-water prokaryotic activity might be primarily associated with particles. Our present knowledge indicates that the microbial communities and their interactions in the deep ocean are likely very different from those known from surface waters. Increasing efforts to shed light on the microbial biota of the ocean's interior will likely lead to the discovery of novel metabolic pathways in prokaryotes and to the resolution of the current discrepancy between the geochemical evidence of remineralization rates of organic matter and actual measurements. 

  • 34. Johansen, J.F.
    et al.
    Blackburn, N.
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Zweifel, Ulla Li
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Hagström, Åke
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Large Variability in Motility Characteristics among Marine Bacteria.2002In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 28, p. 229-237Article in journal (Refereed)
  • 35.
    Johansson, Mona
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Distribution of the Dinoflagellate parasite Parvilucifera infectans (Parkinsozoa) along the Swedish coast2006In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 43, no 3, p. 289-302Article in journal (Refereed)
    Abstract [en]

    Dinoflagellate parasites, e.g. Parvilucifera infectans Noren et Moestrup, 1996 can potentially control dinoflagellate blooms and thereby modify plankton communities and nutrient fluxes. Parvilucifera infectans has been detected in Swedish waters, but its distribution is largely unknown. Based on 18S rRNA sequences of 2 P. infectans isolates of different geographic origin (Sweden and Tasmania), we designed 2 primer pairs for specific PCR amplification of rRNA fragments from these parasites. We screened for presence of F infectans in a salinity gradient along the Swedish coastline (2 to 30 parts per thousand, 13 stations) from June to August 2004. Parasites were only detected in July and August at 3 stations in the region with highest salinity (Skagerrak). Presence of parasites was correlated with high abundances of dinoflagellate hosts (Prorocentrum spp., Ceratium spp.) but was also restricted to warm and saline waters. In addition, these stations were characterized by low bacterial abundances, low chl a and low nutrient levels. Parasites were not detected in this region in June, when temperatures were lower (< 15 degrees C) and microzooplankton predators were most abundant. Hence, our study reveals both temporal and spatial patchiness of P. infectans in coastal waters.

  • 36. Karhunen, Jatta
    et al.
    Arvola, Lauri
    Peura, Sari
    Tiirola, Marja
    Green sulphur bacteria as a component of the photosynthetic plankton community in small dimictic humic lakes with an anoxic hypolimnion2013In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 68, no 3, p. 267-272Article in journal (Refereed)
    Abstract [en]

    High bacteriochlorophyll (BChl) concentrations in the anoxic water layers of some humic lakes have indicated that green sulphur bacteria (GSB) may be ecologically significant. The abundance and spatial distribution of GSB were therefore addressed in 13 small humic lakes using fragment analysis and sequencing of PCR-amplified 16S rRNA genes. GSB were detected from lakes where the photosynthetically active radiation was at least 1.1 ?E m-2 s-1 at the oxic-anoxic boundary layer. In these lakes, 13 to 42% of the 16S rRNA gene sequences of the anoxic water column were assigned to GSB. The spatial distribution of GSB was tightly correlated with the spectrophotometrically measured BChl concentration during the summer season. Maximum BChl concentrations were observed in the uppermost part of the anoxic water layer, covering most of the chlorophyll pigment in these lakes. The GSB of the humic lakes typically belonged to a phylogenetically homogenous group closely related to Chlorobium clathratiforme.

  • 37.
    Kaur-Kahlon, G.
    et al.
    University of Gothenburg.
    Kumar, S.
    Indien.
    Rehnstam-Holm, Ann-Sofi
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Rai, A.
    Indien.
    Bhavya, P. S.
    Indien.
    Edler, L.
    WEAQ Lab, Ängelholm.
    Singh, A.
    University of Gothenburg.
    Andersson, B.
    University of Gothenburg.
    Karunasagar, I.
    Indien.
    Ramesh, R.
    Indien.
    Godhe, A.
    University of Gothenburg.
    Response of a coastal tropical pelagic microbial community to changed salinity and temperature2016In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 77, no 1, p. 37-50Article in journal (Refereed)
    Abstract [en]

    Studies on the responses of tropical microbial communities to changing hydrographic conditions are presently poorly represented. We present here the results from a mesocosm experiment conducted in southwest (SW) coastal India to investigate how changes in temperature and salinity may affect a coastal tropic microbial community. The onset of algal and bacterial blooms, the maximum production and biomass, and the interrelation between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up featuring ambient conditions (28 °C, 35 PSU), hyposalinity (31 PSU), warming (31 °C) and a double manipulated treatment with warming and hyposalinity (31 °C, 31 PSU). The hyposaline treatment had the most considerable influence manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulated treatment and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model approach, and found a significant interrelation between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation with subsequent significant effects on the quantity of microbial biomass and production.

  • 38. Langenheder, Silke
    et al.
    Kisand, Veljo
    Lindström, Eva S
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Tranvik, Lars J
    Growth dynamics within bacterial communities in riverine and estuarine batch cultures2004In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 37, no 2, p. 137-148Article in journal (Refereed)
    Abstract [en]

    We investigated temporal changes in community composition of bacteria growing on riverine dissolved organic carbon. Batch cultures were adjusted to riverine or estuarine salinity levels and inoculated with bacteria from these 2 environments to test whether growth patterns of bacterial taxa are influenced by salinity and/or the source of the inoculum. Changes in bacterial community composition at different stages of the growth phase were studied by 16S rDNA denaturing gradient gel electrophoresis (DGGE). Furthermore, the growth dynamics of 7 bacteria previously isolated from the estuary were followed by quantitative DNA-DNA hybridization. Growth dynamics within bacterial communities were significantly influenced by the source of the inoculum but not by salinity, suggesting that slight changes in salinity, to which riverine bacteria are exposed when discharged into the Northern Baltic Sea, are not a major regulating factor of community dynamics. Additionally, our results indicated only minor differences in the appearance and growth of bacteria when examined by quantitative DNA-DNA hybridization, whereas DGGE banding patterns suggested that there were fast- and slow-growing types of bacteria.

  • 39.
    Lebret, Karen
    et al.
    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.
    Colinas, Noemi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Swedish Univ Agr Sci, Dept Aquat Resources, Öregrund, Sweden.
    Lindström, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Increased water colour affects freshwater plankton communities in a mesocosm study2018In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 81, no 1, p. 1-17Article in journal (Refereed)
    Abstract [en]

    Increases in water colour (brownification) have been observed in aquatic systems in the Northern Hemisphere, partly caused by increased loading of organic carbon from terrestrial origins. We investigated the effect of increase in water colour on the composition, structure and function of lake plankton communities (bacteria, phytoplankton and zooplankton) conducting a mesocosm experiment in 3 medium-coloured lakes (average absorbance at 420 nm: 0.034 cm(-1)), with different nutrient concentrations and phytoplankton community composition. To simulate an increase in water colour, we added humic substances (HuminFeed) at 3 different concentrations. The additions significantly affected the water colour of the mesocosms, but had no measurable effect on total organic carbon concentration, thus change in light conditions was the main effect of our treatment on the plankton communities. The increase in water colour did not significantly affect the measured functions (productivity, respiration) and biomass of the plankton communities (bacteria, phytoplankton and zooplankton), but led to changes in the relative abundance of some phytoplankton taxa and, to a lesser extent, the bacterial community (differences in relative abundance). The treatments had no significant effect on zooplankton biomass or composition. Our study suggests that increases in water colour favour low-light-adapted phytoplankton species, which in turn also can affect bacterial composition, whereas the change in light climate had no clear impact on the functioning of plankton communities in weakly humic lakes.

  • 40.
    Lebret, Karen
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Uppsala University.
    Langenheder, Silke
    Uppsala University.
    Colinas, Noemi
    Uppsala University.
    Östman, Örjan
    Swedish University of Agricultural Sciences.
    Lindström, Eva S.
    Uppsala University.
    Increased water colour affects freshwater plankton communities in a mesocosm study2018In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 81, no 1, p. 1-17Article in journal (Refereed)
    Abstract [en]

    Increases in water colour (brownification) have been observed in aquatic systems in the Northern Hemisphere, partly caused by increased loading of organic carbon from terrestrial origins. We investigated the effect of increase in water colour on the composition, structure and function of lake plankton communities (bacteria, phytoplankton and zooplankton) conducting a mesocosm experiment in 3 medium-coloured lakes (average absorbance at 420 nm: 0.034 cm(-1)), with different nutrient concentrations and phytoplankton community composition. To simulate an increase in water colour, we added humic substances (HuminFeed) at 3 different concentrations. The additions significantly affected the water colour of the mesocosms, but had no measurable effect on total organic carbon concentration, thus change in light conditions was the main effect of our treatment on the plankton communities. The increase in water colour did not significantly affect the measured functions (productivity, respiration) and biomass of the plankton communities (bacteria, phytoplankton and zooplankton), but led to changes in the relative abundance of some phytoplankton taxa and, to a lesser extent, the bacterial community (differences in relative abundance). The treatments had no significant effect on zooplankton biomass or composition. Our study suggests that increases in water colour favour low-light-adapted phytoplankton species, which in turn also can affect bacterial composition, whereas the change in light climate had no clear impact on the functioning of plankton communities in weakly humic lakes.

  • 41.
    Lindström, Eva S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    del Giorgio, Paul A.
    Départment des sciences biologiques, Université du Québec à Montréal (UQÀM), Montréal, QC H3C 3P8, Canada .
    Progress and perspectives in aquatic microbial ecology: highlights of the SAME 14, Uppsala, Sweden, 20152017In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 80, p. 101-103Article in journal (Refereed)
    Abstract [en]

    The presentations and discussion during the Symposium of Aquatic Microbial Ecology (SAME) in Uppsala, Sweden, in August 2015 highlighted new directions and challenges in the study of aquatic microbial communities. In this virtual Special Issue, plenary speakers and meeting awardees explore these challenges. The contributions cover a wide range of topics from the use of molecular analyses of microbial communities to cultivation and stoichiometric analyses. The virtual Special also includes theoretical developments on the concept of rarity to community assembly. A common theme for the Special is, however, the importance of a combination of different approaches in order to deepen our understanding of the ecology of microbial communities.

    The full text will be freely available from 2022-11-24 14:31
  • 42.
    Lundgren, Veronica
    et al.
    Linnéuniversitetet, Institutionen för naturvetenskap, NV.
    Granéli, Edna
    Linnéuniversitetet, Institutionen för naturvetenskap, NV.
    Influence of altered light conditions and grazers on Scrippsiella trochoidea (Dinophyceae) cyst formation2011In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 63, no 3, p. 231-243Article in journal (Refereed)
    Abstract [en]

    We investigated whether or not the presence of copepods and different light conditions induced cyst ­formation in dinoflagellates. Scrippsiella trochoidea was exposed to Acartia tonsa directly and indirectly (grazer filtrate), in high light and low light conditions. The ingestion, faecal ­production and egg production of A. tonsa were compared between diets of S. trochoidea vegetative cells and temporary cysts. We found no effect of direct or indirect exposure to A. tonsa on S. ­trochoidea cyst formation in either high light or low light conditions. Controls and A. tonsa treatments kept in light displayed around 20% temporary cysts, whereas controls and A. tonsa treatments in low light were shown to have 50 to 80% temporary cysts. Thus, low light conditions had a strong effect on ­temporary cyst formation. No hypnocysts were observed in any experiment, which is probably related to the longer incubation times needed for their observation. Feeding on diets dominated by temporary cysts compared to vegetative cells decreased ingestion by a factor of 2.7, while faecal and egg production decreased by a factor of 2.2 and 2.9, respectively, suggesting that induction of temporary cysts in response to A. tonsa could be a survival strategy. However, S. trochoidea does not ­possess any grazer-induced defence in terms of temporary cyst formation, as it did not produce ­temporary cysts when exposed to A. tonsa. Rather, induction of temporary cysts seems to be controlled by decreased light intensity, which is a favorable trait for this species when driven to water depths where light is scarce.

  • 43.
    Lundgren, Veronica
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Granéli, Edna
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Influence of altered light conditions and grazers on Scrippsiella trochoidea (Dinophyceae) cyst formation2011In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 63, no 3, p. 231-243Article in journal (Refereed)
    Abstract [en]

    We investigated whether or not the presence of copepods and different light conditions induced cyst ­formation in dinoflagellates. Scrippsiella trochoidea was exposed to Acartia tonsa directly and indirectly (grazer filtrate), in high light and low light conditions. The ingestion, faecal ­production and egg production of A. tonsa were compared between diets of S. trochoidea vegetative cells and temporary cysts. We found no effect of direct or indirect exposure to A. tonsa on S. ­trochoidea cyst formation in either high light or low light conditions. Controls and A. tonsa treatments kept in light displayed around 20% temporary cysts, whereas controls and A. tonsa treatments in low light were shown to have 50 to 80% temporary cysts. Thus, low light conditions had a strong effect on ­temporary cyst formation. No hypnocysts were observed in any experiment, which is probably related to the longer incubation times needed for their observation. Feeding on diets dominated by temporary cysts compared to vegetative cells decreased ingestion by a factor of 2.7, while faecal and egg production decreased by a factor of 2.2 and 2.9, respectively, suggesting that induction of temporary cysts in response to A. tonsa could be a survival strategy. However, S. trochoidea does not ­possess any grazer-induced defence in terms of temporary cyst formation, as it did not produce ­temporary cysts when exposed to A. tonsa. Rather, induction of temporary cysts seems to be controlled by decreased light intensity, which is a favorable trait for this species when driven to water depths where light is scarce.

  • 44.
    Lymer, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Vrede, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Nutrient additions resulting in phage release and formation of non-nucleoid-containing bacteria2006In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 43, no 2, p. 107-112Article in journal (Refereed)
    Abstract [en]

    The responses of aquatic bacteriophages to (1) P additions in P-limited batch cultures and (2) separate P and N additions in batch cultures that were both P- and N-limited were monitored. Possible connections between the abundance of non-nucleoid-containing cells (non-Nu CC) and viral abundance were also examined. The water used in the experiments was collected from the mesotrophic Lake Erken (Sweden) in late autumn. In both experiments, nutrient addition resulted in increases in viral abundance and non-nucleoid-containing bacterial cells. However, in the P- and N-limited cultures, P addition resulted in increases in viral abundance and non-nucleoid-containing bacterial cells, but no increase in bacterial abundance. In contrast, in the cultures to which N was added, increases in viral abundance were accompanied by increases in the abundance of both bacteria and non-nucleoid-containing cells. The results show that there is a connection between changes in the abundance of viruses and non-nucleoid-containing cells. However, there are indications that viral abundance can change in response to changes in the P status of the environment without any increase in bacterial abundance.

  • 45.
    Mathisen, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Thelaus, J
    Sjöstedt de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rapid adaptation of predation resistance in bacteria isolated from a seawater microcosm2016In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 78, no 2, p. 81-92Article in journal (Refereed)
    Abstract [en]

    Bacterial defense against protozoan grazing has been shown to occur in many different bacteria. Predation resistance traits may however be plastic, making bacterial com munities resilient or resistant to predation perturbations. We studied the adaptation of pre dation resistance traits in bacteria isolated from a microcosm experiment. In the initial microcosm ex periment the predation pressure on bacteria varied markedly, while changes in the bacterial community composition could not be verified. Seven bacteria were isolated from the microcosm (Micrococcus sp., Rhodobacter sp., Paracoccus sp., Shewanella sp., Rhizobium sp. and 2 un identified species) and these were repeatedly exposed to high predation by the ciliate Tetrahymena pyriformis. High variations in edibility and rate of adaptation of predation resistance traits were observed among the strains. The initial mortality rate of the different bacterial taxa and the change over time varied by a factor of 7 and 24, respectively. Rhodobacter sp. was already predation resistant at the start of the experiment and did not change much over time, while Micrococcus sp., Paracoccus sp. and Shewanella sp. initially were relatively edible and later developed predation resistance. In conclusion, we show that rapid adaptation of predation resistance traits is common among bacteria in an aquatic microbial community, and that a single test of a bacterium’s edibility will in many cases not be enough to fully understand its ecological role, as it will not reveal the potential adaptive response. The results suggest the potential of rapid changes of predation resistance as a mechanism for bacterial communities to be resilient to variations in predation disturbances.

  • 46. Middelboe, M.
    et al.
    Riemann, Lasse
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Steward, G.F.
    Hansen, V.
    Nybroe, O.
    Virus induced transfer of organic carbon between marine bacteria in a model community2003In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 33, p. 1-10Article in journal (Refereed)
  • 47.
    Minnhagen, Susanna
    et al.
    Linnéuniversitetet, Institutionen för naturvetenskap, NV.
    Kim, Miran
    Chonnam National University, Republic of Korea.
    Salomon, Paulo
    Linnéuniversitetet, Institutionen för naturvetenskap, NV.
    Yih, Wonho
    Kunsan National University, Republic of Korea.
    Granéli, Edna
    Linnéuniversitetet, Institutionen för naturvetenskap, NV.
    Park, Myung Gil
    Chonnam National University, Republic of Korea.
    Active uptake of kleptoplastids by Dinophysis caudata from its ciliate prey Myrionecta rubra2011In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 62, no 1, p. 99-108Article in journal (Refereed)
    Abstract [en]

    We verified an active uptake of kleptoplastids in the toxic and bloom-forming dinoflagellatesof the genus Dinophysis from its preferred prey, the ciliate Myrionecta rubra, using a quantitativereal-time PCR technique. During a 65 d starvation/feeding experiment with Dinophysis caudata,changes in plastid 16S rRNA, plastid autofluorescence and plastid/nuclear DNA ratio throughthe cell cycle were followed with quantitative real-time PCR and flow cytometry. During starvation,the cultures initially showed a rapid growth and a 3.5-fold increase of number of cells ml–1, while atthe same time, plastid DNA cell–1 showed a 3.5-fold decrease, and a 3.6-fold decrease in phycoerythrinfluorescence cell–1. The decrease in plastid DNA cell–1 d–1 closely followed culture growth rate(Pearson correlation, r = 0.91), indicating that existing plastids were diluted within the growing populationand that no new plastids were synthesised by the cells. When starved cells were re-fed by theciliate M. rubra on Days 43 to 51 of the experiment, plastid DNA cell–1 increased 7-fold up to 14 00016S DNA copies per cell, thereby directly revealing the kleptoplastic behaviour. The implication isthat not only availability of the prey M. rubra itself, but also the supply of suitable kleptoplastidsmight be an important controlling factor for Dinophysis spp. bloom formation and decline.

  • 48.
    Minnhagen, Susanna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Kim, Miran
    Chonnam National University, Republic of Korea.
    Salomon, Paulo
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Yih, Wonho
    Kunsan National University, Republic of Korea.
    Granéli, Edna
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Park, Myung Gil
    Chonnam National University, Republic of Korea.
    Active uptake of kleptoplastids by Dinophysis caudata from its ciliate prey Myrionecta rubra2011In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 62, no 1, p. 99-108Article in journal (Refereed)
    Abstract [en]

    We verified an active uptake of kleptoplastids in the toxic and bloom-forming dinoflagellatesof the genus Dinophysis from its preferred prey, the ciliate Myrionecta rubra, using a quantitativereal-time PCR technique. During a 65 d starvation/feeding experiment with Dinophysis caudata,changes in plastid 16S rRNA, plastid autofluorescence and plastid/nuclear DNA ratio throughthe cell cycle were followed with quantitative real-time PCR and flow cytometry. During starvation,the cultures initially showed a rapid growth and a 3.5-fold increase of number of cells ml–1, while atthe same time, plastid DNA cell–1 showed a 3.5-fold decrease, and a 3.6-fold decrease in phycoerythrinfluorescence cell–1. The decrease in plastid DNA cell–1 d–1 closely followed culture growth rate(Pearson correlation, r = 0.91), indicating that existing plastids were diluted within the growing populationand that no new plastids were synthesised by the cells. When starved cells were re-fed by theciliate M. rubra on Days 43 to 51 of the experiment, plastid DNA cell–1 increased 7-fold up to 14 00016S DNA copies per cell, thereby directly revealing the kleptoplastic behaviour. The implication isthat not only availability of the prey M. rubra itself, but also the supply of suitable kleptoplastidsmight be an important controlling factor for Dinophysis spp. bloom formation and decline.

  • 49. Møller, Eva F.
    et al.
    Riemann, Lasse
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Søndergaard, Morten
    Bacteria associated with copepods: abundance, activity and community composition2007In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 47, p. 99-106Article in journal (Refereed)
  • 50.
    Pinhassi, Jarone
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Azam, F.
    Hemphälä, J.
    Long, R.A.
    Martinez, J.
    Zweifel, Ulla Li
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Hagström, Åke
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Coupling between bacterioplankton species compostion, population dynamics, and organic matter degradation.1999In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 17Article in journal (Refereed)
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