Four of these double mutants (wraB/ychN, wraB/osmC, wraB/dcoC and wraB/cbpA) showed a decreased ability to survive when subjected to oxidative stress by H2O2, indicating functional redundancy with these genes for oxidative stress adaptation. In the current study, mutagenesis of ygaU
proved unsuccessful. A comprehensive study of genes of importance for virulence in BALB/c mice has demonstrated that deletion of ygaU is possible, and that the gene is not essential for growth or for mouse virulence . Thus, despite our difficulties, we advocate that this gene this website too, can be considered non-essential for growth and virulence in S. Typhimurium, while no results on stress adaptation are available. ygaU encodes CP673451 in vivo an uncharacterized protein demonstrated to be induced by salt stress in E. coli and to be a novel member of the RpoS regulon in S. Typhimurium . It contains a BON domain, which is characteristic of osmotic shock protection proteins , and a LysM domain, which was first reported in bacterial cell wall degrading enzymes and recently in other proteins with
a variety of functions . In the current investigation, ygaU was found to be significantly regulated in eight tested conditions, but due to our difficulties with construction of a defined mutant we could not assess the importance for stress adaptation. The CbpA protein of S. Typhimurium elicits 89% similarity to the E. coli CbpA -standing for curved selleck chemical DNA-binding protein A- and it is induced when cells approach the stationary phase [31, 32]. It is a DnaJ homolog demonstrated to act as a co-chaperone in conjunction with DnaK . Regulation of CbpA activity is controlled at the transcriptional level by the RpoS and Lrp global regulators and at posttranscriptional level by degradation of CpbM by the Lon and ClpAP proteases Vitamin B12 . In the current investigation, cbpA was significantly regulated in seven tested conditions. The cbpA mutant was found not to show any changes in phenotype
under any of the tested conditions, and four double mutants elicited similar lack of phenotypical changes. However, three other combinations of double mutants showed significantly decreased ability to survive under H2O2 stress (cbpA/wraB, cbpA/yajD and cbpA/osmC mutants). The UspA (universal stress protein A) superfamily is widely distributed in bacteria, Archaea, fungi and plants and in E. coli it is induced under a wide variety of stress factors . The exact function of UspA is somewhat elusive, however, in some cases it appears to be of importance in defense toward DNA damaging agents and respiratory uncouplers . In S. Typhimurium it has been demonstrated that uspA expression is induced during entry into stationary phase and by temperature up-shifts . Furthermore, mutants have been reported to have increased sensitivity towards oxidative stress, most pronounced in the exponential growth phase, and survival in minimal media was impaired .