CONSTRUCTION AND CHARACTERIZATION OF A FIMZ MUTANT OF SALMONELLA-TYPHIMURIUM

The Salmonella typhimurium fimA gene is controlled bg several ancillar y fim genes. One of these genes, fimZ, appears to be involved in incre asing the expression of fimA. A fimZ mutant of S. typhimurium was cons tructed by allelic exchange, and this mutant was found to be nonfimbri ate. The fimZ mutant demonstrated decreased levels of fimA expression compared with the parental strain when both were grown under condition s favoring fimbrial expression, An examination of the predicted amino acid sequence, deduced from the nucleotide sequence of fimZ, indicated that the FimZ polypeptide possessed a DNA binding motif, Bacterial ly sates, derived from strains transformed with recombinant plasmids poss essing a fimZ gene, demonstrated DNA binding activity with a fragment containing the fimA promoter, Lysates without a FimZ polypeptide did n ot exhibit any binding activity, These data are consistent with FimZ b eing a transcriptional activator of fimA, and FimZ acts by binding to the promoter region.