Abstract
Microbial communities in deep subsurface environments
comprise a large portion of Earth's biomass, but the
microbial activity in these habitats is largely unknown.
Here, we studied how microorganisms from two isolated
groundwater fractures at 180 and 500 m depths of the
Outokumpu Deep Drillhole (Finland) responded to methane
or methanol amendment, in the presence or absence of
sulfate as an additional electron acceptor. Methane is a
plausible intermediate in the deep subsurface carbon
cycle, and electron acceptors such as sulfate are
critical components for oxidation processes. In fact, the
majority of the available carbon in the Outokumpu deep
biosphere is present as methane. Methanol is an
intermediate of methane oxidation, but may also be
produced through degradation of organic matter. The
fracture fluid samples were incubated in vitro with
methane or methanol in the presence or absence of sulfate
as electron acceptor. The metabolic response of microbial
communities was measured by staining the microbial cells
with fluorescent redox sensitive dye combined with flow
cytometry, and DNA or cDNA-derived amplicon sequencing.
The microbial community of the fracture zone at the 180 m
depth was originally considerably more respiratory active
and 10-fold more numerous (105 cells ml-1 at 180 m depth
and 104 cells ml-1 at 500 m depth) than the community of
the fracture zone at the 500 m. However, the dormant
microbial community at the 500 m depth rapidly
reactivated their transcription and respiration systems
in the presence of methane or methanol, whereas in the
shallower fracture zone only a small sub-population was
able to utilize the newly available carbon source. In
addition, the composition of substrate activated
microbial communities differed at both depths from
original microbial communities. The results demonstrate
that OTUs representing minor groups of the total
microbial communities play an important role when
microbial communities face changes in environmental
conditions.
Original language | English |
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Article number | Article 431 |
Pages (from-to) | 431 |
Number of pages | 1 |
Journal | Frontiers in Microbiology |
Volume | 8 |
Issue number | March |
DOIs | |
Publication status | Published - 17 Mar 2017 |
MoE publication type | A1 Journal article-refereed |
Keywords
- deep biosphere
- deep life
- carbon
- methane
- methanol
- methanotrophy