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Environ Microbiol. 2017 Feb;19(2):459-474. doi: 10.1111/1462-2920.13362. Epub 2016 Jul 7.

Genomic resolution of a cold subsurface aquifer community provides metabolic insights for novel microbes adapted to high CO2 concentrations.

Author information

1
Department of Earth and Planetary Sciences, University of California, Berkeley, 307 McCone Hall, CA, 94720, USA.
2
Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA.
3
Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA.
4
Earth Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, USA.

Abstract

As in many deep underground environments, the microbial communities in subsurface high-CO2 ecosystems remain relatively unexplored. Recent investigations based on single-gene assays revealed a remarkable variety of organisms from little studied phyla in Crystal Geyser (Utah, USA), a site where deeply sourced CO2 -saturated fluids are erupted at the surface. To provide genomic resolution of the metabolisms of these organisms, we used a novel metagenomic approach to recover 227 high-quality genomes from 150 microbial species affiliated with 46 different phylum-level lineages. Bacteria from two novel phylum-level lineages have the capacity for CO2 fixation. Analyses of carbon fixation pathways in all studied organisms revealed that the Wood-Ljungdahl pathway and the Calvin-Benson-Bassham Cycle occurred with the highest frequency, whereas the reverse TCA cycle was little used. We infer that this, and selection for form II RuBisCOs, are adaptions to high CO2 -concentrations. However, many autotrophs can also grow mixotrophically, a strategy that confers metabolic versatility. The assignment of 156 hydrogenases to 90 different organisms suggests that H2 is an important inter-species energy currency even under gaseous CO2 -saturation. Overall, metabolic analyses at the organism level provided insight into the biochemical cycles that support subsurface life under the extreme condition of CO2 saturation.

PMID:
27112493
DOI:
10.1111/1462-2920.13362
[Indexed for MEDLINE]

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