Leucine-responsive Receptor Protein Acts as an Activator of Salmonella typhimurium fimA
Cole, Allison M.
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Members of the Salmonella genus, belonging to the family Enterobacteriacae, are gram negative, facultatively anaerobic rods, that pose a major health problem worldwide (Hook et al., 1980). Bacteria of this genus are pathogenic to humans and animals, causing a variety of diseases, including food poisoning and enteric fever (Hook et aI., 1980). The fimbrial gene cluster, responsible for phenotypic expression of type 1 fimbriae, has been characterized (Clegg et aI., 1994). The fimA gene encodes FimA, the major fimbrial subunit. In this experiment we begin to examine the role leucine responsive receptor protein, Lrp may have infimA transcription in S. typhimurium and the influence that leucine may have. A 'AjimAlacZ lysogen was constructed using S. typhimurium genes and inserted into E. coli JMI09Iac-lrp+ and E. coli JMI09 lac-lrp strains transformed with pISFI80, a plasmid containing fimZ, fimY, and fimW. The transcriptional activity of the lysogen was measured using p-galactosidase assays. Assays were run on these strains grown in M9 minimal medium supplemented with phenylalanine and thiamine, and half of the cultures were supplemented with leucine. It was found that Lrp is an activator of fimA transcription as demonstrated by the increased enzyme activity in the lrp wild type strains versus the lrp mutants. The role of leucine was unclear. Future studies will include further investigation of Lrp's role in fimA transcription and further elucidation of the fimbrial gene cluster in S. typhimurium.