Affiliation:
1. Dipartimento di Genetica e di Biologia dei Microrganismi, Università degli Studi di Milano, Italy.
Abstract
In order to study the toluene and o-xylene catabolic genes of Pseudomonas stutzeri OX1, a genomic library was constructed. A 28-kb EcoRI restriction endonuclease DNA fragment, cloned into the vector plasmid pLAFR1 and designated pFB3401, permitted Pseudomonas putida PaW340 to convert toluene and o-xylene into the corresponding meta-ring fission products. Physical and functional endonuclease restriction maps have been derived from the cloned DNA fragment. Further subcloning into and deletion analysis in the Escherichia coli vector pGEM-3Z allowed the genes for the conversion of toluene or o-xylene into the corresponding catechols to be mapped within a 6-kb region of the pFB3401 insert and their direction of transcription to be determined. Following exposure to toluene, E. coli cells carrying this 6-kb region produce a mixture of o-cresol, m-cresol, and p-cresol, which are further converted to 3-methylcatechol and 4-methylcatechol. Similarly, a mixture of 2,3-dimethylphenol and 3,4-dimethylphenol, further converted into dimethylcatechols, was detected after exposure to o-xylene. The enzyme involved in the first step of toluene and o-xylene degradation exhibited a broad substrate specificity, being able to oxidize also benzene, ethylbenzene, m-xylene, p-xylene, styrene, and naphthalene. Deletions of the 6-kb region which affect the ability to convert toluene or o-xylene into the corresponding methylphenols compromise also their further oxidation to methylcatechols. This suggests that a single enzyme system could be involved in both steps of the early stages of toluene and o-xylene catabolism.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
99 articles.
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