Influence des conditions de culture préalables et de la présence du gènerpoSpour la survie deSalmonella typhimuriumen eau de mer exposée à la lumière solaire

Abstract

The effect of sunlight exposure on Salmonella typhimurium isogenic strains harboring an rpoS gene functional (rpoS+) or not functional (rpoS-) was investigated in microcosms of sterile sea water at 20 degrees C. The two strains rapidly lost their ability to produce colonies on solid culture media. The detrimental action of sunlight was more important when the salinity of sea water increased. The survival of stationary phase cells was influenced by RpoS. Bacteria grown in media with high salinity or osmolarity and transferred to sea water in stationary phase were more resistant to irradiation than those grown in media with low salinity. Prior growth under oxidative (0.2 mmol/L of H2O2) or amino acid starved (minimal medium) conditions did not modify the survival of either strain when they were exposed to sunlight. Bacteria were more resistant when cells were incubated in sea water in the dark prior to being exposed to sunlight. The resistance to sunlight irradiation was also greater in clones of both strains isolated from microcosms exposed to sunlight for 90 min, then further inoculated into sea water and reexposed to sunlight.

Exposure to low UVA doses increases KatA and KatB catalase activities, and confers cross-protection against subsequent oxidative injuries in Pseudomonas aeruginosa

“…In addition, mutant strains of E. coli deficient in the excision repair system (uvr) are highly sensitive to UVA (Webb & Brown, 1976;Shennan et al, 1996), and similar results were obtained in strains of Salmonella and E. coli defective for RecA, the protein responsible for expression of genes involved in the SOS response (Eisenstark, 1970;Webb & Brown, 1976). The RpoS protein, the alternative sigma transcription factor involved in general stress responses during the stationary growth phase, is also involved in UVA defence both in enterobacteria and Pseudomonas syringae (Miller et al, 2001;Maatouk et al, 2004;Berney et al, 2006b). Studies of global gene expression during UVA adaptation in bacteria such as E. coli, Shewanella oneidensis and Enterococcus faecalis showed activation of the genes coding for antioxidant enzymes ahpCF, ahpC and sodA (Qiu et al, 2005;Berney et al, 2006a;Sassoubre et al, 2014); however, induction of genes coding for main catalases was not a common element in these studies.…”

INFLUENCE OF MARINE WATER CONDITIONS ON SALMONELLA ENTERICA SEROVAR TYPHIMURIUM SURVIVAL

“…may also depend on the species, origin and source of contamination (Troussellier 1998; Lesne et al . 2000; Rozen and Belkin 2001; Maatouk et al . 2004; Chandran and Mohamed Hatha 2005).…”