Microbial mineralization of ethene under sulfate-reducing conditions

Previous investigations demonstrated that respiratoly reductive dechlorination of vinyl chloride (VC) can be efficient even at H₂ concentrations (≤2 nM) that are characteristic of SO₄-reducing conditions. In the study reported here, microorganisms indigenous to a lake-bed sediment completely mineralized [1,2-¹⁴C] ethene to ¹⁴14CO₂ when incubated under SO₄-reducing conditions. Together, these observations argue for a novel mechanism for the net anaerobic oxidation of VC to CO₂: reductive dechlorination of VC to ethene followed by anaerobic oxidation of ethene to CO₂. Moreover, the results of this study suggest that reliance on ethene and/or ethane accumulation as a quantitative indicator of complete reductive dechlorination of chioroethene contaminants may not be warranted.