Degradation of phenol and m-toluate in Pseudomonas sp. strain EST1001 and its Pseudomonas putida transconjugants is determined by a multiplasmid system

Abstract

The utilization of phenol, m-toluate, and salicylate (Phe+, mTol+, and Sal+ characters, respectively) in Pseudomonas sp. strain EST1001 is determined by the coordinated expression of genes placed in different plasmids, i.e., by a multiplasmid system. The natural multiplasmid strain EST1001 is phenotypically unstable. In its Phe-, mTol-, and Sal- segregants, the plasmid DNA underwent structural rearrangements without a marked loss of plasmid DNA, and the majority of segregants gave revertants. The genes specifying the degradation of phenol and m-toluate were transferable to P. putida PaW340, and in this strain a new multiplasmid system with definite structural changes was formed. The 17-kilobase transposable element, a part of the TOL plasmid pWWO present in the chromosome of PaW340, was inserted into the plasmid DNA in transconjugants. In addition, transconjugant EST1020 shared pWWO-like structures. Enzyme assays demonstrated that ortho-fission reactions were used by bacteria that grew on phenol, whereas m-toluate was catabolized by a meta-fission reaction. Salicylate was a functional inducer of the enzymes of both pathways. The expression of silent metabolic pathways of phenol or m-toluate degradation has been observed in EST1001 Phe- mTol+ and Phe+ mTol- transconjugants. The switchover of phenol degradation from the ortho- to the meta-pathway in EST1033 also showed the flexibility of genetic material in EST1001 transconjugants.