The metabolic range of the solvent-resistant bacterium, Pseudomonas putida S12, was successfully expanded by transferring into it catabolic plasmids for the degradation of toluene, biphenyl and naphthalene. Enhancement of the catabolic possibilities of P. putida S12 strain does not interfere with its toluene resistance properties. In this way we obtained derivatives which are able to use the heterologous genes in a two-phase system.