| Summary: | Ethyl tert-butyl ether (ETBE) is a gasoline additive that became an important aquifer pollutant. The information about natural bacterial consortia with a capacity for complete ETBE degradation is limited. Here we assess the taxonomical composition of bacterial communities and diversity of the <i>ethB</i> gene (involved in ETBE biodegradation) in ETBE-enrichment cultures that were established from a gasoline-polluted aquifer, either from anoxic ETBE-polluted plume water (PW), or from an upstream non-polluted water (UW). We used a 16S rRNA microarray, and 16S rRNA and <i>ethB</i> gene sequencing. Despite the dissimilar initial chemical conditions and microbial composition, ETBE-degrading consortia were obtained from both PW and UW. The composition of ETBE-enrichment cultures was distinct from their initial water samples, reflecting the importance of the rare biosphere as a reservoir of potential ETBE degraders. No convergence was observed between the enrichment cultures originating from UW and PW, which were dominated by <i>Mesorhizobium</i> and <i>Hydrogenophaga</i>, respectively, indicating that distinct consortia with the same functional properties may be present at one site. Conserved <i>ethB</i> genes were evidenced in both PW and UW ETBE-enrichment cultures and in PW water. Our results suggest that the presence of <i>ethB</i> genes rather than the taxonomical composition of in situ bacterial communities indicate the potential for the ETBE degradation at a given site.
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