Some evidences for the involvement of plasmid in diuron herbicide degradation

Pseudomonas sp. strain Bk8 was isolated from field soil contaminated with different urea-herbicides. This strain is a plasmid (pBkB)-harbouring organism capable of complete degradation of diuron herbicide. Plasmid-cured strain Bk8M was obtained by treatment of Pseudomonas sp. Bk8 with Mitomycin C. This cured strain is capable of only partial degradation of diuron side chain and accumulated a phenolic compound in the medium during growing on diuron as a sole source of carbon and energy. Conjugation experiment was carried out using Bk8M as a recipient and Bk8 as a donor of pBk8 plasmid. The transconjugant was able to degrade a diuron without accumulation of phenolic compound. It was proposed that plasmid pBk8 is self-transmissible and involved in the degradation of diuron aromatic ring but it is not connected with the transformation of diuron into diuron phenol compound.