title: Stable and Variable Parts of Microbial Community in Siberian Deep Subsurface Thermal Aquifer System Revealed in a Long-Term Monitoring Study.
abstract: The goal of this work was to study the diversity of microorganisms inhabiting a deep subsurface aquifer system in order to understand their functional roles and interspecies relations formed in the course of buried organic matter degradation. A microbial community of a deep subsurface thermal aquifer in the Tomsk Region, Western Siberia was monitored over the course of 5 years via a 2.7 km deep borehole 3P, drilled down to a Palaeozoic basement. The borehole water discharges with a temperature of ca. 50°C. Its chemical composition varies, but it steadily contains acetate, propionate, and traces of hydrocarbons and gives rise to microbial mats along the surface flow. Community analysis by PCR-DGGE 16S rRNA genes profiling, repeatedly performed within 5 years, revealed several dominating phylotypes consistently found in the borehole water, and highly variable diversity of prokaryotes, brought to the surface with the borehole outflow. The major planktonic components of the microbial community wereDesulfovirgula thermocuniculiandMethanothermobacterspp. The composition of the minor part of the community was unstable, and molecular analysis did not reveal any regularity in its variations, except some predominance of unculturedFirmicutes. Batch cultures with complex organic substrates inoculated with water samples were set in order to enrich prokaryotes from the variable part of the community. PCR-DGGE analysis of these enrichments yielded unculturedFirmicutes, Chloroflexi, andIgnavibacteriae. A continuous-flow microaerophilic enrichment culture with a water sample amended with acetate containedHydrogenophilus thermoluteolus, which was previously detected in the microbial mat developing at the outflow of the borehole. Cultivation results allowed us to assume that variable components of the 3P well community are hydrolytic organotrophs, degrading buried biopolymers, while the constant planktonic components of the community degrade dissolved fermentation products to methane and CO2, possibly via interspecies hydrogen transfer. Occasional washout of minor community components capable of oxygen respiration leads to the development of microbial mats at the outflow of the borehole where residual dissolved fermentation products are aerobically oxidized. Long-term community analysis with the combination of molecular and cultivation techniques allowed us to characterize stable and variable parts of the community and propose their environmental roles.
authors.affiliation: Department of Plant Physiology and Biotechnology, Tomsk State University Tomsk, Russia.
authors.forename: Yulia A
authors.initials: YA
authors.lastname: Frank
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Institute of Bioengineering Moscow, Russia.
authors.forename: Vitaly V
authors.initials: VV
authors.lastname: Kadnikov
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences (RAS) Moscow, Russia.
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Gavrilov
authors.affiliation: Glasgow and Holymoor Consultancy Ltd., Glasgow University Chesterfield, UK.
authors.forename: David
authors.initials: D
authors.lastname: Banks
authors.affiliation: Department of Plant Physiology and Biotechnology, Tomsk State University Tomsk, Russia.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Gerasimchuk
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences (RAS) Moscow, Russia.
authors.forename: Olga A
authors.initials: OA
authors.lastname: Podosokorskaya
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences (RAS) Moscow, Russia.
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Merkel
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences (RAS) Moscow, Russia.
authors.forename: Nikolai A
authors.initials: NA
authors.lastname: Chernyh
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Institute of Bioengineering Moscow, Russia.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Mardanov
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Institute of Bioengineering Moscow, Russia.
authors.forename: Nikolai V
authors.initials: NV
authors.lastname: Ravin
authors.affiliation: Department of Plant Physiology and Biotechnology, Tomsk State University Tomsk, Russia.
authors.forename: Olga V
authors.initials: OV
authors.lastname: Karnachuk
authors.affiliation: Federal Research Centre (FRC) Biotechnology, Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences (RAS) Moscow, Russia.
authors.forename: Elizaveta A
authors.initials: EA
authors.lastname: Bonch-Osmolovskaya
keywords: Western Siberia; deep subsurface; element cycles and biogeochemical processes; phylogenetic analysis; thermophilic microbial communities