Microbial metagenomes from three aquifers in the Fennoscandian shield terrestrial deep biosphere reveal metabolic partitioning among populations.
Microorganisms in the terrestrial deep biosphere host up to 20% of the earth's biomass and are suggested to be sustained by the gases hydrogen and carbon dioxide. A metagenome analysis of three deep subsurface water types of contrasting age (from <20 to several thousand years) and depth (171 to 448 m) revealed phylogenetically distinct microbial community subsets that either passed or were retained by a 0.22 μm filter. Such cells of <0.22 μm would have been overlooked in previous studies relying on membrane capture. Metagenomes from the three water types were used for reconstruction of 69 distinct microbial genomes, each with >86% coverage. The populations were dominated by Proteobacteria, Candidate divisions, unclassified archaea and unclassified bacteria. The estimated genome sizes of the <0.22 μm populations were generally smaller than their phylogenetically closest relatives, suggesting that small dimensions along with a reduced genome size may be adaptations to oligotrophy. Shallow 'modern marine' water showed community members with a predominantly heterotrophic lifestyle. In contrast, the deeper, 'old saline' water adhered more closely to the current paradigm of a hydrogen-driven deep biosphere. The data were finally used to create a combined metabolic model of the deep terrestrial biosphere microbial community.
Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
Xiaofen
X
Wu
Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
Karin
K
Holmfeldt
Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
Valerie
V
Hubalek
Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
Daniel
D
Lundin
Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
Mats
M
Åström
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, Kalmar, Sweden.
Mark
M
Dopson
D001419:Bacteria / Q000235:genetics*; D044822:Biodiversity; D005075:Biological Evolution; D018533:Biomass; D019295:Computational Biology; D060587:Groundwater; D054892:Metagenome; D064307:Microbiota; D010802:Phylogeny; D025341:Principal Component Analysis; D020560:Proteobacteria / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013548:Sweden; D014871:Water Microbiology