Plasmid-encoded degradation of p-nitrophenol by Pseudomonas cepacia

A Pseudomonas cepacia strain RKJ 200 capable of utilising p-nitrophenol (PNP+) as the sole source of carbon, nitrogen, and energy was isolated by selective enrichment. The degradation of PNP by this strain proceeds through an oxidative route as indicated by the accumulation of nitrite molecules in the culture medium. Initial studies indicate that the degradation of PNP occurs via hydroquinone as shown by thin layer chromatography and gas chromatography studies; hydroquinone is further degraded via the beta-ketoadipate pathway. A plasmid of approximately 50 kilobase pairs was found to be responsible for carrying genes for PNP degradation in this strain. This was based on the facts that the PNP- mutants lacked the plasmid and that the PNP+ phenotype could conjugally be transferred. In addition, the same plasmid also encoded resistance to inorganic zinc ions.