Transcriptional analysis of therpoEgene encoding extracytoplasmic stress response sigma factor σ^EinSalmonella entericaserovar Typhimurium

Abstract

The rpoE gene of Salmonella enterica serovar Typhimurium (S. Typhimurium), which encodes the extracytoplasmic stress response sigma factor c E , is critically important for the virulence of S. Typhimurium. We analysed expression of rpoE by wild-type and mutant bacteria grown in different conditions by S1-nuclease mapping using RNA, and using in vivo reporter gene fusions. Three promoters, rpoEp1, rpoEp2 and rpoEp3, were located upstream of the S. Typhimurium rpoE gene. The promoters were differentially expressed during growth and under several stress conditions including cold shock. Expression from the rpoEp3 promoter was absent in an S. Typhimurium rpoE mutant, demonstrating its dependence upon c E . The level of mRNA corresponding to rpoEp3 was also higher in a cpxR mutant, indicating a negative regulation of the promoter by the Cpx system. Using this rpoE-dependent promoter, we optimised a two-plasmid system for identification of promoters recognised by S. Typhimurium c E . The rpoEp3 promoter was active in the Escherichia coli twoplasmid system and has an identical transcription start point as in S. Typhimurium but only after induction of S. Typhimurium rpoE expression.

Role of the alternative sigma factors σ E and σ S in survival of Salmonella enterica serovar Typhimurium during starvation, refrigeration and osmotic shock

“…Recently a large number of genes have been shown, or are suspected, to be s E -regulated in S. Typhimurium and E. coli. These include genes encoding proteins concerned with envelope homeostasis such as periplasmic proteases and folding factors but also many genes of unknown function that are predicted to encode inner-and outer-membrane proteins and genes that function in the cytoplasm (Rezuchova et al, 2003;Bang et al, 2005;Kabir et al, 2005;Rhodius et al, 2006;Skovierova et al, 2006). These genes can be targeted to determine which are important for coping with the stresses reported in this study.…”

“…2b). The importance of rpoE for survival at 4.5 u C suggests that, in S. Typhimurium, at least, some genes involved in prolonging survival at refrigeration temperatures are s E -regulated (Miticka et al, 2003;Rezuchova et al, 2003). Recently a large number of genes have been shown, or are suspected, to be s E -regulated in S. Typhimurium and E. coli.…”

“…Cold-shock activates the stress-response regulons in E. coli and Salmonella enterica serovar Typhimurium (S. Typhimurium) controlled by the alternative sigma factors RpoE (s E ) and RpoS (s S ) (Loewen & Hengge-Aronis, 1994;Munro et al, 1995;Kandror et al, 2002;Miticka et al, 2003;Polissi et al, 2003). These studies suggest that s E and s S may be important for survival of S. Typhimurium at low temperature, but this has not been investigated.…”

“…Another stress relevant to food processing known to activate expression of both s E and s S dependent genes in E. coli and S. Typhimurium is hyperosmotic shock (HenggeAronis et al, 1993;Hengge-Aronis, 1996;Bianchi & Baneyx, 1999;Miticka et al, 2003;Balaji et al, 2005). However, again there has been little or no work on the role of s E and s S on the growth/survival of S. enterica in hyperosmotic environments.…”

Shifts from glucose to certain secondary carbon-sources result in activation of the extracytoplasmic function sigma factor σ E in Salmonella enterica serovar Typhimurium

“…Previous studies indicate that, once activated, s E initiates the transcription of several genes with extracytoplasmic functions required for the cell envelope to combat the effects of the stress. In the absence of stress, s E is normally bound to the inner-membrane (IM) protein RseA, an anti-sigma factor or inhibitor of s E , preventing its interaction with RNA polymerase, and thus the transcription of s E -dependent genes (De Las Penas et al, 1997;Missiakas et al, 1997;Alba et al, 2002, Miticka et al, 2003. When a specific stress occurs to the cell envelope, RseA is degraded by DegS and YaeL, s E is then released and is able to bind to core RNA polymerase (E).…”