Due to its high chemical stability, the biodegradation of benzene is the most challenging amongst hydrocarbons. While oxygen-dependent oxygenases are employed by aerobic bacteria to overcome the energy barrier, the mechanism of anaerobic benzene biodegradation is still enigmatic. The sulfate-reducing, clonal enrichment culture BzS1 is capable of benzene degradation under anoxic conditions. In addition, the alkylbenzene toluene may be used as sole source of carbon and energy. In this project, the protein complements of the soluble as well as membrane protein-enriched fractions of cells of strain BzS1 adapted to anaerobic growth with benzene or toluene, respectively, were studied.