Anaerobic benzene degradation by iron- and sulfate-reducing enrichment cultures

Anaerobic benzene degradation was studied with a sulfate- and an iron-reducing enrichment culture (BPL and BF). In culture BPL, molecular analysis revealed 95% dominance of a novel phylotype that is affiliated to the genus Pelotomaculum. To elucidate the initial activation mechanism of anaerobic benzene degradation, putative metabolites were screened revealing benzoate as a product of a carboxylation reaction. For identification of enzymes involved in anaerobic benzene degradation the whole proteomes expressed in benzene-, phenol-, and benzoate-grown cells of culture BF were separated by SDS gels. A specific benzene-expressed protein band with a mass of 60 kDa was identified by N-terminal sequencing. The amino acid sequence was similar to known carboxylases. A combined shotgun genome sequencing together with a proteomic analysis identified a cluster of ORFs containing the same putative anaerobic benzene carboxylase (Abc) enzyme. The respective putative genes were also identified from the proteome of culture BPL suggesting that carboxylation is a common activation mechanism in anaerobic benzene degradation.