title: Inducibility of the TOL catabolic pathway in Pseudomonas putida (pWW0) growing on succinate in continuous culture: evidence of carbon catabolite repression control.
abstract: The TOL catabolic genes in Pseudomonas putida (pWW0) are clustered in the upper operon, encoding enzymes for the conversion of toluene and xylenes to benzoate and toluates, and the meta-cleavage operon, encoding enzymes for the conversion of the benzoate and toluates to tricarboxylic acid cycle intermediates. In this study, it was shown that cells growing in a chemostat under succinate growth-limiting conditions express both the upper and meta-cleavage pathways in response to o-xylene, a nonmetabolizable effector of the XylR regulatory protein. The dilution rate maintained in the succinate-limited chemostat cultures influenced the synthesis levels of TOL pathway enzymes, their steady-state levels, and their turnover rates. Cells growing in the presence of nonlimiting concentrations of succinate in continuous culture did not express pathway enzymes in response to the addition of o-xylene, which was due to a blockage at the transcriptional level. Expression of the meta-cleavage pathway in response to 2,3-dimethylbenzoate, a nonmetabolizable effector of the XylS regulatory protein, was 93% lower in cultures exposed to succinate at nonlimiting concentrations than in the succinate-limited chemostats. The mRNA level of xylS during nonlimited growth on succinate was very low compared with that in succinate-limited cultures, suggesting that suppression of expression of the meta-cleavage pathway is regulated mainly by the level of the XylS regulator.
authors.affiliation: Laboratory for Waste Materials and Emissions, National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.
authors.forename: W A
authors.initials: WA
authors.lastname: Duetz
authors.forename: S
authors.initials: S
authors.lastname: Marqués
authors.forename: C
authors.initials: C
authors.lastname: de Jong
authors.forename: J L
authors.initials: JL
authors.lastname: Ramos
authors.forename: J G
authors.initials: JG
authors.lastname: van Andel
mesh_terms: D001483:Base Sequence; D001565:Benzoates / Q000494:pharmacology; D003470:Culture Media; D004794:Enzyme Repression / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005798:Genes, Bacterial / Q000502:physiology; D007700:Kinetics; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism*; D019802:Succinic Acid; D014992:Xylenes / Q000378:metabolism*
chemical_list: D001565:Benzoates; D003470:Culture Media; D013386:Succinates; D014992:Xylenes; C086734:2,3-dimethylbenzoic acid; D019802:Succinic Acid; C026114:2-xylene