Bacterial Degradation of Chlorinated Biphenyls

Abstract

Chlorinated biphenyls are widely used in industry and agriculture. These compounds are known to cause teratogenic effects and are widely distributed in the environment. Bacterial strains degrading chlorinated biphenyls were isolated by enrichment and direct screening procedures from activated sewage and polychlorinated biphenyl- (PCB) contaminated soils. The PCB-degrading bacteria were tentatively identified as Pseudomonas, Aeromonas, Achromobacter, Alcaligenes, Enterobacter, Bacillus, and gram-positive pleomorphic rods. These PCB-degrading bacterial strains were resistant to several antibiotics including newer β-lactam antibiotics (imipenem, moxalactam, cephoxitin, cefizoxine, and aztreonam). The electrophoretic pattern of plasmid DNAs from these strains showed presence of plasmids (molecular weight ranging 2 to >40 Mdal). Thin layer Chromatographic analysis of the water-soluble metabolites of 4-chlorobiphenyl by resting cell suspension of Pseudomonas putida (strain 83) and gram-positive bacteria (strain OBS23) showed different metabolites of Rf value: 0.71, 0.78, 0.83, 0.14, 0.18, 0.37, 0.53, 0.60, and 0.69, respectively. The gas Chromatographic analysis and ultraviolet absorption spectrum of water-soluble metabolites of 2,3- and 4-chlorinated biphenyls showed accumulation of benzoic acid and 2,3- and 4-chlorobenzoic acid, respectively. Our results demonstrate that PCB can be degraded by pure culture of bacteria and further suggest a preliminary evidence of reductive dehalogenation of chlorobiphenyls with P. putida strain 83.