Microbial co-occurrence patterns in deep Precambrian bedrock fracture fluids
The bacterial and archaeal community composition and the possible carbon assimilation processes and energy sources of microbial communities in oligotrophic, deep, crystalline bedrock fractures is yet to be resolved. In this study, intrinsic microbial communities from groundwater of six fracture zone...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-05-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/3091/2016/bg-13-3091-2016.pdf |
| Summary: | The bacterial and archaeal community composition and the possible carbon
assimilation processes and energy sources of microbial communities in
oligotrophic, deep, crystalline bedrock fractures is yet to be resolved. In
this study, intrinsic microbial communities from groundwater of six fracture
zones from 180 to 2300 m depths in Outokumpu bedrock were characterized using
high-throughput amplicon sequencing and metagenomic prediction.
<i>Comamonadaceae</i>-, <i>Anaerobrancaceae</i>- and <i>Pseudomonadaceae</i>-related operational taxonomic units (OTUs) form the core community in deep crystalline bedrock
fractures in Outokumpu. Archaeal communities were mainly composed of
<i>Methanobacteriaceae</i>-affiliating OTUs. The predicted bacterial metagenomes showed that pathways
involved in fatty acid and amino sugar metabolism were common. In addition,
relative abundance of genes coding the enzymes of autotrophic carbon
fixation pathways in predicted metagenomes was low. This indicates that
heterotrophic carbon assimilation is more important for microbial
communities of the fracture zones. Network analysis based on co-occurrence
of OTUs revealed possible “keystone” genera of the microbial communities
belonging to <i>Burkholderiales</i> and <i>Clostridiales</i>. Bacterial communities in fractures resemble those found
in oligotrophic, hydrogen-enriched environments. Serpentinization
reactions of ophiolitic rocks in Outokumpu assemblage may provide a source
of energy and organic carbon compounds for the microbial communities in the
fractures. Sulfate reducers and methanogens form a minority of the total
microbial communities, but OTUs forming these minor groups are similar to
those found in other deep Precambrian terrestrial bedrock environments. |
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| ISSN: | 1726-4170 1726-4189 |