Coexistence of Psychrophilic, Mesophilic, and Thermophilic Sulfate-Reducing Bacteria in a Deep Subsurface Aquifer Associated with Coal-Bed Methane Production

The microbial community of subsurface environments remains understudied due to limited access to deep strata and aquifers. Coal-bed methane (CBM) production is associated with a large number of wells pumping water out of coal seams. CBM wells provide access to deep biotopes associated with coal-bed water. Temperature is one of the key constraints for the distribution and activity of subsurface microorganisms, including sulfate-reducing prokaryotes (SRP). The 16S rRNA gene amplicon sequencing coupled with in situ sulfate reduction rate (SRR) measurements with a radioactive tracer and cultivation at various temperatures revealed that the SRP community of the coal bed water of the Kuzbass coal basin is characterized by an overlapping mesophilic-psychrophilic boundary. The genus Desulfovibrio comprised a significant share of the SRP community. The D. psychrotolerans strain 1203, which has a growth optimum below 20 degrees C, dominated the cultivated SRP. SRR in coal bed water varied from 0.154 +/- 0.07 to 2.04 +/- 0.048 nmol S cm(-3) day(-1). Despite the ambient water temperature of similar to 10-20 degrees C, an active thermophilic SRP community occurred in the fracture water, which reduced sulfate with the rate of 0.159 +/- 0.023 to 0.198 +/- 0.007 nmol S cm(-3) day(-1) at 55 degrees C. A novel moderately thermophilic Desulforudis audaxviator-clade SRP has been isolated in pure culture from the coal-bed water.

Automated summary

This study explored the microbial community of coal bed water and found an overlapping mesophilic-psychrophilic boundary, dominated by the Desulfovibrio genus and the D. psychrotolerans 1203 strain. Additionally, the researchers discovered an active thermophilic community in the fracture water, reducing sulfate at a rate of 0.159 to 0.198 nmol S cm(-3) day(-1) at 55 degrees C.