Localization and functional analysis of transposon mutations in regulatory genes of the TOL catabolic pathway

Abstract

Mutant derivatives of the TOL plasmid pWW0-161, containing [transposon] Tn5 insertions in the xylS and xylR regulatory genes of the catabolic pathway, were identified and characterized. The 2 genes are located together on a 1.5-3.0-kilobase segment of TOL, just downstream of genes of the enzymes of the meta-cleavage pathway. As predicted by a current model for regulation of the TOL catabolic pathway, benzyl alcohol dehydrogenase, a representative enzyme of the upper (hydrocarbon .fwdarw. carboxylic acid) pathway, was induced by m-methylbenzyl alcohol in xylS mutant bacteria but not in a xylR mutant, whereas catechol 2,3-oxygenase, a representative enzyme of the lower (meta-cleavage) pathways, was induced by m-toluate in a xylR mutant but not in the xylS mutants. Catechol 2.3-oxygenase was not induced by m-methylbenzyl alcohol in xylS mutants but was induced by benzyl alcohol and benzoate. These results indicate that expression of the TOL plasmid-encoded catabolic pathway is regulated by at least 3 control elements, 2 of which (the products of the xylS and xylR genes) interact in the induction of the lower pathway by methylated hydrocarbons and alcohols, and one of which responds only to nonmethylated substrates. [Escherichia coli and Pseudomonas putula were used.].