Involvement of two plasmids in the degradation of carbaryl by Arthrobacter sp. strain RC100

A bacterium capable of utilizing carbaryl (1-naphthyl N-methylcarbamate) as the sole carbon source was isolated from carbaryl-treated soil. This bacterium was characterized taxonomically as Arthrobacter and was designated strain RC100. RC100 hydrolyzes the N-methylcarbamate linkage to 1-naphthol, which was further metabolized via salicylate and gentisate. Strain RC100 harbored three plasmids (designated pRC1, pRC2, and pRC3). Mutants unable to degrade carbaryl arose at a high frequency after treating the culture with mitomycin C. All carbaryl-hydrolysis-deficient mutants (Cah(-)) lacked pRC1, and all 1-naphthol-utilization-deficient mutants (Nat(-)) lacked pRC2. The plasmid-free strain RC107 grew on gentisate as a carbon source. These two plasmids could be transferred to Cah(-) mutants or Nat(-) mutants by conjugation, resulting in the restoration of the Cah and Nah phenotypes.