Abstract: Two microorganisms, which utilize phenol as a sole source of carbon and energy, were isolated from an enrichment culture. The microorganisms were identified as Pseudomonas sp. and Staphylococcus sp. The bacterial strains were found to harbor three endogenous plasmids. Two of the plasmids were lost when the microorganisms were treated with ethidium bromide. Loss of the plasmids in the organisms were correlated with the loss of the ability to metabolize phenol. Phenotypic testing of the wild type and cured strains revealed that the gene(s) responsible for phenol degradation may reside upon the plasmids.