Relationship between phenylcarbamate degradation and plasmids in two strains of Pseudomonas

Two strains of soil bacteria, Pseudomonas cepacia and Pseudomonas alcaligenes, which degrade herbicides have been isolated. Both contain plasmids whose presence is correlated with the capacity to metabolise phenylcarbamates. Successive subculturing in the absence of herbicide or curing my mitomycin C leads to the loss of small plasmids from both strains associated with modifications in herbicide degradation. Further, the level of the smallest plasmid of P. cepacia increases when CIPC is the sole carbon source. This plasmid hybridises to several larger molecular species, suggesting a certain degree of structural rearrangement in response to the presence of the herbicide.