Rhodococcus erythropolis TA421, a polychlorinated biphenyl and biphenyl degrader isolated from a termite
ecosystem, has seven bphC genes expressing 2,3-dihydroxybiphenyl dioxygenase activity. R. erythropolis TA421
harbored a large and probably linear plasmid on which three (bphC2, bphC3, and bphC4) of the seven bphC
genes were located. A non-biphenyl-degrading mutant, designated strain TA422, was obtained spontaneously
from R. erythropolis TA421. TA422 lacked the plasmid, suggesting that the three bphC genes were involved in
the degradation of biphenyl. Southern blot analyses showed that R. erythropolis TA421 and Rhodococcus
globerulus P6 have a similar set of bphC genes and that the genes for biphenyl catabolism are located on
plasmids of different sizes. These results indicated that the genes encoding the biphenyl catabolic pathway in
Rhodococcus strains are borne on plasmids.