IDENTIFICATION OF A NEW PRP LOCUS REQUIRED FOR PROPIONATE CATABOLISM IN SALMONELLA-TYPHIMURIUM LT2

A new propionate (prp) locus of S. typhimurium was defined by mutation , was located to minute 8 of the chromosome, and was shown to be trans cribed in the clockwise direction. A plasmid carrying the wild-type pr p(+) locus was isolated by complementation, and its initial physical c haracterization is presented. Transcriptional regulation of prp was st udied using MudI1734(lacZ(+)) operon fusions. Propionate stimulated pr p transcription in a merodiploid strain containing prp(+) and a prp::M udI1734 fusion, but failed to stimulate transcription of the same fusi on in a haploid genetic background. prp transcription was reduced by a factor of 2 in strains deficient in the synthesis of the global regul atory protein FruR; fruR mutants failed to grow on propionate. Propion ate blocked growth of prp mutants on medium containing succinate as ca rbon/energy source.