GENE-EXPRESSION IN RESPONSE TO MULTIPLE NUTRIENT-STARVATION CONDITIONS IN SALMONELLA-TYPHIMURIUM

In nature, bacteria encounter a variety of environmental conditions, among the most frequent of these is the limitation or starvation of one or more essential nutrients. It is reasonable to assume, therefore, that bacteria have evolved mechanisms to enhance their survival over prolonged periods of nutrient starvation. We have identified eight genetic loci in the enteropathogen Salmonella typhimurium, using Mu d-directed lacZ operon fusion technology, that were induced in response to two or more different starvation conditions (sti). In simultaneous studies, we also identified genetic loci, using Mu d-lac fusion, which respond to only phosphate-starvation conditions (psi). We further characterized these loci as to their induction-characteristics, kinetics of induction, expression during growth on different carbon sources, and approximate location on the S. typhimurium genetic map. In concurrent studies, we analyzed whole cell extracts of S. typhimurium grown under a variety of nutrient starvation conditions as well as under nonlimiting conditions, using two-dimensional polyacrylamide gel electrophoresis. Results from these studies correlated well with our gene fusion studies. In more recent studies, we have demonstrated a complex genetic regulation of a number of these starvation-inducible loci, and have implicated at least four of these loci in the long term starvation-survival of S. typhimurium.