Potential for hydrogen-oxidizing chemolithoautotrophic and diazotrophic populations to initiate biofilm formation in oligotrophic, deep terrestrial subsurface waters.
Deep terrestrial biosphere waters are separated from the light-driven surface by the time required to percolate to the subsurface. Despite biofilms being the dominant form of microbial life in many natural environments, they have received little attention in the oligotrophic and anaerobic waters found in deep bedrock fractures. This study is the first to use community DNA sequencing to describe biofilm formation under in situ conditions in the deep terrestrial biosphere.



In this study, flow cells were attached to boreholes containing either "modern marine" or "old saline" waters of different origin and degree of isolation from the light-driven surface of the earth. Using 16S rRNA gene sequencing, we showed that planktonic and attached populations were dissimilar while gene frequencies in the metagenomes suggested that hydrogen-fed, carbon dioxide- and nitrogen-fixing populations were responsible for biofilm formation across the two aquifers. Metagenome analyses further suggested that only a subset of the populations were able to attach and produce an extracellular polysaccharide matrix. Initial biofilm formation is thus likely to be mediated by a few bacterial populations which were similar to Epsilonproteobacteria, Deltaproteobacteria, Betaproteobacteria, Verrucomicrobia, and unclassified bacteria.



Populations potentially capable of attaching to a surface and to produce extracellular polysaccharide matrix for attachment were identified in the terrestrial deep biosphere. Our results suggest that the biofilm populations were taxonomically distinct from the planktonic community and were enriched in populations with a chemolithoautotrophic and diazotrophic metabolism coupling hydrogen oxidation to energy conservation under oligotrophic conditions.
Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, 391 82, Kalmar, Sweden.
Xiaofen
X
Wu
Microbial Analytics Sweden AB, Mölnlycke, Sweden.
Karsten
K
Pedersen
Microbial Analytics Sweden AB, Mölnlycke, Sweden.
Johanna
J
Edlund
Microbial Analytics Sweden AB, Mölnlycke, Sweden.
Lena
L
Eriksson
Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
Mats
M
Åström
KTH Royal Institute of Technology, Science for Life Laboratory, School of Biotechnology, Stockholm, Sweden.
Anders F
AF
Andersson
Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
Stefan
S
Bertilsson
Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, 391 82, Kalmar, Sweden. mark.dopson@lnu.se.
Mark
M
Dopson
D020562:Betaproteobacteria / Q000145:classification / Q000235:genetics*; D018441:Biofilms / Q000145:classification*; D052837:Chemoautotrophic Growth / Q000235:genetics* / Q000502:physiology; D020564:Deltaproteobacteria / Q000145:classification / Q000235:genetics*; D020565:Epsilonproteobacteria / Q000145:classification / Q000235:genetics*; D000071251:Extreme Environments; D060587:Groundwater / Q000382:microbiology; D006859:Hydrogen / Q000737:chemistry; D054892:Metagenome; D009586:Nitrogen Fixation / Q000235:genetics* / Q000502:physiology; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D061327:Verrucomicrobia / Q000145:classification / Q000235:genetics*; D014871:Water Microbiology
D012336:RNA, Ribosomal, 16S; D006859:Hydrogen
16S rRNA gene; Binning; Biofilm formation; Deep biosphere; Metabolism; Metagenome; Terrestrial