A NOVEL TRANSFORMATION OF POLYCHLORINATED-BIPHENYLS BY RHODOCOCCUS SPSTRAIN RHA1

We have characterized a biphenyl degrader, Rhodococcus sp. strain RHA1 . Biphenyl-grown cells of strain RHA1 efficiently transformed 45 compo nents in the 62 major peaks of a polychlorinated biphenyl (PCB) mixtur e of Kanechlors 200, 300, 400, and 500 within 3 days, which includes m ono- to octachlorobiphenyls. Among the intermediate metabolites of PCB transformation, di- and trichlorobenzoic acids were identified. The g radual decrease of these chlorobenzoic acids during incubation indicat ed that these chlorobenzoic acids would also be degraded by this strai n. The effect of the position of chlorine substitution was determined by using PCB mixtures that have chlorine substitutions mainly at eithe r the ortho or the meta position. This strain transformed both types o f congeners, and strong PCB transformation activity of RHA1 was indica ted. RHA1 accumulated 4-chlorobenzoic acid temporally during the trans formation of 4-chlorobiphenyl, The release of most chloride in the cou rse of 2,2'-dichlorobiphenyl degradation was observed. These results s uggested that RHA1 would break down at least some PCB congeners into s maller molecules to a considerable extent.