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Functional Microbial Diversity Explains Groundwater Chemistry in a Pristine Aquifer
Citation:
Flynn, T. M., R. A. Sanford, H. RYU, C. M. Bethke, A. D. Devine, N. ASHBOLT, AND J. W. SANTO-DOMINGO. Functional Microbial Diversity Explains Groundwater Chemistry in a Pristine Aquifer. BMC Microbiology. BioMed Central Ltd, London, Uk, 13:146, (2013).
Impact/Purpose:
To inform the public.
Description:
Microbial communities inhabiting anoxic aquifers catalyze critical biogeochemical reactions in the subsurface, yet little is known about how their community structure correlates with groundwater chemistry. In this study, we described the composition of microbial communities in the Mahomet aquifer of east-central Illinois using 16S rRNA gene sequencing and examine how the groundwater chemistry controls the distribution of bacteria and archaea. Nearly 17, 000 bacterial and archaeal sequences were analyzed from both the sediment-associated and groundwater fractions of the aquifer. The data indicate clear differences in community structure between suspended and attached bacterial and archaeal populations in the subsurface, suggesting the importance of monitoring both microbial fractions when studying subsurface microbial processes. Statistical analyses showed that the composition of bacterial and archaeal communities in the wells analyzed was strongly correlated to the concentration of both sulfate. Clones related to sulfate-reducing bacterial species, such as Desulfobacter and Desulfobulbus spp., represented 16% of the bacterial community in wells with sulfate concentrations >0.2 mM, compared to only 3–12% in wells with less sulfate. Conversely, populations closely related to the iron reducing bacteria Geobacter were more prevalent in areas where the concentration of sulfate was less than 0.03 mM, representing 34% of all sequences there compared with 15–22% in higher sulfate wells. Archaeal 16S rRNA gene sequences associated with the methanogen groups Methanosarcinaceae and Methanosaetaceae comprised 73–80% of the archaeal community in areas where sulfate concentrations were depleted (<0.03 mM). These methanogens were nearly absent in samples collected from groundwater samples with >0.2 mM sulfate. The archaeal community was instead dominated by sequences from a novel lineage close to the ANME-2D group, known for anaerobic methane oxidation. Their presence and the lack of other apparent energy sources for metabolism suggest that this type of metabolism may be occurring in this aquifer potentially coupled to sulfate reduction. Overall, the results from this study point to a clear link between groundwater chemistry and microbial community structure.
