Conjugal transfer of a TOL-like plasmid and extension of the catabolic potential of Pseudomonas putida F1

Strain mX was isolated from a petrol-contaminated soil, after enrichment on minimal medium with 0.5% (v/v) meta-xylene as a sole carbon source. The st rain was tentatively characterized as Pseudomonas putida and harboured a la rge plasmid (pMX) containing xyl genes involved in toluene or meta-xylene d egradation pathways via an alkyl monooxygenase and a catechol 2,3-dioxygena se. This new TOL-like plasmid was stable over two hundred generations and w as self-transferable. After conjugal transfer to P. putida F1, which posses ses the Tod chromosomal toluene biodegradative pathway, the transconjugant P. putida F1(pMX) was able to grow on benzene, toluene, meta-xylene, para-x ylene, and ethylbenzene compounds as the sole carbon sources. Catechol 2,3- dioxygenases of the transconjugant cells presented a more relaxed substrate specificity than those of parental cells (strain mX and P. putida F1).