MULTIPLE POLYCHLORINATED BIPHENYL TRANSFORMATION SYSTEMS IN THE GRAM-POSITIVE BACTERIUM RHODOCOCCUS SP STRAIN RHA1

The cloned bphA gene of the polychlorinated biphenyl (PCB) degrader Rh odococcus sp. strain RHA1 was expressed in Rhodococcus erythropolis IA M1399 cells, resulting in the transformation of di-, tri-, and tetrach lorobiphenyls. Disruption of the bphAI gene in RHA1 resulted in a lack of growth on biphenyl and a loss of PCB transformation activity. Howe ver, the bphA1 insertion mutant of RHA1, designated RDA1, retained the ability to transform PCB congeners when grown on ethylbenzene as its carbon source. It also transformed 4-chlorobiphenyl to l-chlorobenzoat e, although it was suspected to be deficient in bphB and bphC gene act ivities as well as bphA. This suggested that an alternative PCB degrad ation system distinct from the one encoded by the cloned bph genes was present.