SALMONELLA-TYPHIMURIUM LOCI INVOLVED IN SURVIVAL WITHIN MACROPHAGES

A set of Tn10 mutants of Salmonella typhimurium which have a diminishe d capacity to survive in murine macrophages and decreased virulence in mice has been described previously. In this study, we characterized 3 0 of these mutants and determined map locations of Tn10 insertions for 23 of these strains. In addition, short fragments of transposon-flank ing DNA were cloned, and the nucleotide sequence was determined for 23 mutants. Seven mutants carried transposon insertions in known genes, representing six loci: htrA, prc, purD, fliD, nagA, and smpB. The poss ible roles of these genes in Salmonella virulence are discussed. One i nsertion was found to be in an unknown gene which shared homology with the open reading frames Bv' and Bv located in the pin inversion syste m of Shigella boydii. In one mutant, Tn10 was found to be inserted in a gene with significant homology to adhE of Escherichia coli and Clost ridium acetobutylicum. The map location and degree of homology indicat e that the Salmonella gene encodes a related but different, dehydrogen ase. In 14 of the mutants analyzed, Tn10 was inserted into genes which had no significant homologies to entries in the DNA and protein data bases. In conclusion, 16 insertions define loci, termed ims for impair ed macrophage survival, which have not yet been described in S. typhim urium but have been shown previously to be necessary for full virulenc e in mice. Although most ims loci are distributed randomly throughout the genome, a cluster was found between 75 and 78 min on the Salmonell a chromosome.