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Genomics, physiology and applications of cold tolerant acidophiles
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Psychrotolerant acidophiles have gained increasing interest because of their importance in biomining operations in environments where the temperature falls well below 10°C during large parts of the year.

Acidithiobacillus ferrivorans is the only characterized acidophile with the ability to live a psychrotrophic lifestyle and is able to oxidize ferrous iron and inorganic sulfur compounds at low temperature. The A. ferrivorans SS3 genome sequence mirrors its low temperature chemolithotrophic lifestyle and indicates ecological flexibility. Two enzyme systems for the synthesis of the protective molecule trehalose as well as multiple cold shock proteins suggest its psychrotolerance. In addition to genes coding for ferrous iron and inorganic sulfur compound oxidation enzymes, candidate genes for molecular hydrogen utilization were identified. Also, A. ferrivorans SS3 was suggested to have the ability to switch between nitrogen fixation and nitrogen uptake. Characterization of ferrous iron and inorganic sulfur compound oxidation during low temperature growth showed that both substrates were efficiently oxidized and revealed the potential of using ferric iron as an alternative electron acceptor. Gene transcript analyses also revealed constitutive expression of genes involved in ferrous iron oxidation and their rapid increase in expression when ferrous iron became available. Growth experiments further suggested ferrous iron was preferred over inorganic sulfur compounds during bioleaching. This phenomenon was especially evident during A. ferrivorans-mediated bioleaching of chalcopyrite as sulfur accumulated and eventually inhibited further leaching. A potential way to alleviate this problem is addition of low temperature, obligate inorganic sulfur compound oxidizing acidophiles. Although, these microorganisms have not been identified, analysis of a cold, acidic biofilm from Kristineberg mine suggested additional psychrotolerant inorganic sulfur compound oxidation oxidizers might be present. Psychrotolerant acidophiles from Kristineberg mine have also been demonstrated to remove inorganic sulfur compounds from mining process water at in situ temperatures. This use of indigenous microorganisms for removal of environmental pollutants is a big step towards greener mining.

Abstract [sv]

Syra-älskande bakterier, s.k. acidofiler, är mikroorganismer som lever i ofta metallrika miljöer med väldigt lågt pH. Dom används industriellt i en process kallad biolakning där metaller utvinns från mineral genom den katalyserande förmågan hos dessa mikroorganismer.

Acidithiobacillus ferrivorans är en nyligen karaktäriserad acidofil som oxiderar järn- och svavelföreningar vid låga temperaturer, den första och hittills enda av sitt slag. Den har visat sig väldigt användbar vid biolakning i kalla miljöer, såsom i Sveriges norra delar där medeltemperaturen sjunker under 10°C under stora delar av året. En inblick i den genetiska potentialen hos denna mikroorganism avspeglar dess livsstil samt avslöjar en bred ekologisk flexibilitet. Ett flertal gener kan sammankopplas med dess förmåga att överleva vid låga temperaturer, såsom gener för tillverkning av s.k. köldchockproteiner. Vid sidan om gener som kodar för järn- och svaveloxiderande enzymer återfinns potentialen att oxidera vätgas. A. ferrivorans verkar även kunna växla mellan att fixera kvävgas och ta upp kvävejoner ifrån sin omgivande miljö, beroende på den tillgängliga kvävekällan. Vidare karaktärisering av järn- och svaveloxidering vid låga temperaturer visade att båda typer av substrat kan oxideras effektivt men avslöjar även att svaveloxidering kan sammankopplas med reducering av järn istället för den traditionella syrgasen. Analys av genuttryck visade att gener för järnoxidering var kontinuerligt uttryckta och att en signifikant uppreglering sker så snart järn introduceras. Det visade sig även att järn verkar vara det föredragna substratet vid biolakning. Detta fenomen är speciellt uppenbart under biolakningsexperiment med A. ferrivorans då elementärt svavel succesivt ackumuleras och så småningom hindrar vidare frigörelse av metaller. En lösning på detta problem skulle kunna vara att tillsätta köldtoleranta mikroorganismer med enbart svaveloxiderande förmåga. Idag finns inte några sådana bakterier beskrivna, men analys utav en kontinuerligt kyld och sur biofilm isolerad ifrån Kristinebergsgruvan indikerar emellertid förekomsten av svaveloxiderande bakterier. Köldtoleranta acidofiler från Kristinebergsgruvan har även visat sig användbara vid industriellt avlägsnande av svavelföreningar från gruvindustriellt processvatten. Att använda naturligt förekommande mikroorganismer vid rening av miljöfarligt avfall är ett stort steg i riktning mot en grönare gruvindustri.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2012. , 69 p.
National Category
Microbiology
Identifiers
URN: urn:nbn:se:umu:diva-60550ISBN: 978-91-7459-472-0 (print)OAI: oai:DiVA.org:umu-60550DiVA: diva2:561082
Public defence
2012-11-22, Norrlands universitetssjukhus, Major Groove, NUS, Umeå, 09:00
Opponent
Supervisors
Available from: 2012-11-01 Created: 2012-10-16 Last updated: 2012-10-18Bibliographically approved
List of papers
1. Draft genome of the psychrotolerant acidophile Acidithiobacillus ferrivorans SS3
Open this publication in new window or tab >>Draft genome of the psychrotolerant acidophile Acidithiobacillus ferrivorans SS3
2011 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 193, no 16, 4304-4305 p.Article in journal (Refereed) Published
Abstract [en]

Acidithiobacillus ferrivorans SS3 is a psychrotolerant acidophile capable of growth in the range of 5° to 30°C (optimum, ≈25°C). It gains energy from the oxidation of ferrous iron and inorganic sulfur compounds and obtains organic carbon from carbon dioxide. Here, we present the draft genome sequence of A. ferrivorans SS3 that will permit investigation of genes involved in growth in acidic environments at low temperatures.

Place, publisher, year, edition, pages
American Society for Microbiology, 2011
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-56530 (URN)10.1128/JB.05373-11 (DOI)21705598 (PubMedID)
Available from: 2012-06-20 Created: 2012-06-20 Last updated: 2017-12-07Bibliographically approved
2. Oxidation of elemental sulfur, tetrathionate and ferrous iron by the psychrotolerant Acidithiobacillus strain SS3.
Open this publication in new window or tab >>Oxidation of elemental sulfur, tetrathionate and ferrous iron by the psychrotolerant Acidithiobacillus strain SS3.
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2009 (English)In: Research in Microbiology, ISSN 0923-2508, E-ISSN 1769-7123, Vol. 160, no 10, 767-74 p.Article in journal (Refereed) Published
Abstract [en]

Mesophilic iron and sulfur-oxidizing acidophiles are readily found in acid mine drainage sites and bioleaching operations, but relatively little is known about their activities at suboptimal temperatures and in cold environments. The purpose of this work was to characterize the oxidation of elemental sulfur (S(0)), tetrathionate (S4O6(2-)) and ferrous iron (Fe2+) by the psychrotolerant Acidithiobacillus strain SS3. The rates of elemental sulfur and tetrathionate oxidation had temperature optima of 20 degrees and 25 degrees C, respectively, determined using a temperature gradient incubator that involved narrow (1.1 degrees C) incremental increases from 5 degrees to 30 degrees C. Activation energies calculated from the Arrhenius plots were 61 and 89 kJ mol(-1) for tetrathionate and 110 kJ mol(-1) for S(0) oxidation. The oxidation of elemental sulfur produced sulfuric acid at 5 degrees C and decreased the pH to approximately 1. The low pH inhibited further oxidation of the substrate. In media with both S(0) and Fe2+, oxidation of elemental sulfur did not commence until all available ferrous iron was oxidized. These data on sequential oxidation of the two substrates are in keeping with upregulation and downregulation of several proteins previously noted in the literature. Ferric iron was reduced to Fe2+ in parallel with elemental sulfur oxidation, indicating the presence of a sulfur:ferric iron reductase system in this bacterium.

Place, publisher, year, edition, pages
Elsevier, 2009
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-58311 (URN)10.1016/j.resmic.2009.08.022 (DOI)19782750 (PubMedID)
Available from: 2012-08-30 Created: 2012-08-29 Last updated: 2017-12-07Bibliographically approved
3. Gene identification and substrate regulation provides insights into sulfur accumulation during bioleaching with the psychrotolerant Acidithiobacillus ferrivorans
Open this publication in new window or tab >>Gene identification and substrate regulation provides insights into sulfur accumulation during bioleaching with the psychrotolerant Acidithiobacillus ferrivorans
(English)Manuscript (preprint) (Other academic)
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-60547 (URN)
Available from: 2012-10-16 Created: 2012-10-16 Last updated: 2016-02-25
4. Metagenomic analysis reveals adaptations to a psychrotrophic lifestyle in a low temperature acid mine drainage stream
Open this publication in new window or tab >>Metagenomic analysis reveals adaptations to a psychrotrophic lifestyle in a low temperature acid mine drainage stream
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-60548 (URN)
Available from: 2012-10-16 Created: 2012-10-16 Last updated: 2016-02-25
5. Low temperature removal of inorganic sulfur compounds from mining process waters
Open this publication in new window or tab >>Low temperature removal of inorganic sulfur compounds from mining process waters
2011 (English)In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 108, no 6, 1251-1259 p.Article in journal (Refereed) Published
Abstract [en]

Process water and effluents from mining operations treating sulfide rich ores often contain considerable concentrations of metastable inorganic sulfur compounds such as thiosulfate and tetrathionate. These species may cause environmental problems if released to downstream recipients due to oxidation to sulfuric acid catalyzed by acidophilic microorganisms. Molecular phylogenic analysis of the tailings pond and recipient streams identified psychrotolerant and mesophilic inorganic sulfur compound oxidizing microorganisms. This suggested year round thiosalt oxidation occurs. Mining process waters may also contain inhibiting substances such as thiocyanate from cyanidation plants. However, toxicity experiments suggested their expected concentrations would not inhibit thiosalt oxidation by Acidithiobacillus ferrivorans SS3. A mixed culture from a permanently cold (4-6°C) low pH environment was tested for thiosalt removal in a reactor design including a biogenerator and a main reactor containing a biofilm carrier. The biogenerator and main reactors were successively reduced in temperature to 5-6°C when 43.8% of the chemical oxidation demand was removed. However, it was found that the oxidation of thiosulfate was not fully completed to sulfate since low residual concentrations of tetrathionate and trithionate were found in the discharge. This study has demonstrated the potential of using biotechnological solutions to remove inorganic sulfur compounds at 6°C and thus, reduce the impact of mining on the environment. Biotechnol. Bioeng. 2011; 108:1251-1259. © 2011 Wiley Periodicals, Inc.

Keyword
Acidithiobacillus ferrivorans;psychrotolerant;thiosulfate;bioremediation;continuous process
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-43231 (URN)10.1002/bit.23057 (DOI)21280027 (PubMedID)
Available from: 2011-04-22 Created: 2011-04-22 Last updated: 2017-12-11Bibliographically approved

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