This research was supported by Agencia Nacional de Promoción Científica y Tecnológica and Universidad Nacional de Quilmes. M.E.L. and J.A.T. are research members at CONICET; C.W.R. is a CONICET fellow, Argentina. Maria Luján Cuestas is also gratefully acknowledged for her kind participation in the scientific revision of this manuscript. We appreciated Valeria Cappa’s collaboration in some experimental works. “
“Division of Natural Sciences, St. Norbert

College, De Pere, WI, USA Salmonella enterica can survive harsh environmental conditions, including hyperosmotic stress. It is well established that the alternative sigma factor, σs (RpoS), is required for maximal survival of enteric pathogens, including S. enterica. Although RpoS levels are greatest during stationary phase or stress conditions, RpoS can be found in S. enterica Luminespib nmr during growth. However, its activity during growth is poorly characterized. In this study, the impact of RpoS levels on the growth of S. enterica in LB supplemented

with 6% NaCl (LB-NaCl) was examined. Cells in stationary phase prior to inoculation into LB-NaCl had a shorter lag phase than Ferrostatin-1 solubility dmso did exponential-phase cells. In addition, the deletion of rpoS from S. enterica Typhimurium M-09 (M-09 ΔrpoS) increased the length of lag phase in LB-NaCl relative to the parental strain. Complementation of M-09 ΔrpoS in trans by an inducible plasmid encoding 4��8C rpoS reduced the length of lag phase. The length of lag phase in both the rpoS mutant and complemented strain was independent of their growth phase prior to inoculation of LB-NaCl. The results from this study demonstrate that the level of RpoS influences the length of lag phase and the growth of S. enterica in hyperosmotic growth conditions. “
“Citrobacter rodentium is a mouse pathogen that, because of its similarities with human enteropathogenic (EPEC) and enterohemorrhagic (EHEC) strains of Escherichia coli is widely used as a model system for in vivo and in vitro studies. Similarly

to EPEC and EHEC, C. rodentium carries the LEE (locus of enterocyte effacement) pathogenicity island, encoding virulence factors essential for causing transmissible colonic hyperplasia in mice by attaching and effacing (A/E) lesions. Expression of the genes carried by the LEE pathogenicity island is controlled by complex networks of transcriptional factors, including the global regulators H-NS, IHF, and Fis. In this study, we analyzed the role of Lrp, another global regulator of gene expression in enteric bacteria, on the expression of LEE genes of C. rodentium. To this aim, a real-time PCR approach was used and revealed a negative role of Lrp on the expression of all analyzed LEE genes. Mobility-shift experiments indicated that Lrp action is direct on LEE1 and indirect on all other analyzed LEE genes.