Anaerobic biodegradation of BTEX by original bacterial communities from an underground gas storage aquifer.

BTEX biodegradation by an indigenous deep subsurface microbial community was evaluated in a water sample collected in the area of an underground gas storage. Five different sulfate-reducing microbial communities able to use at least either benzene, toluene, ethylbenzene, or xylene (BTEX) compounds were studied. A total of 21 different bacterial phylotypes were identified, each community containing three to nine bacterial phylotypes. Archaeal phylotypes were retrieved from only three communities. The analysis of 16S rRNA gene sequences showed that i) these consortia were mainly composed of novel species, some of which belonging to bacterial groups not previously suspected to be involved in BTEX anaerobic degradation, ii) three consortia were dominated by an uncultured Pelobacter sp. previously detected in biodegraded oil reservoirs, iii) a deeply branching species distantly affiliated to Thermotogales was abundant in two consortia, and that iv) Firmicutes related to the Desulfotomaculum and Carboxydocella genera represented the only three detectable phylotypes in a toluene-degrading consortium. This work shows that subdominant microbial populations present in a deep subsurface aquifer used for seasonal underground gas storage could be involved in the natural attenuation of the traces of BTEX coinjected with methane in the deep subsurface.