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Effect of Growth Temperature on Crl-Dependent Regulation of σS Activity in Salmonella enterica Serovar Typhimurium▿

By Véronique Robbe-Saule, Ingrid Carreira, Annie Kolb and Françoise Norel


The small regulatory protein Crl favors association of the stationary-phase sigma factor σS (RpoS) with the core enzyme polymerase and thereby increases σS activity. Crl has a major physiological impact at low levels of σS. Here, we report that the Crl effects on σS-dependent gene expression, the H2O2 resistance of Salmonella enterica serovar Typhimurium, and the resistance of this organism to acidic pH are greater at 28°C than at 37°C. Immunoblot experiments revealed a negative correlation between σS and Crl levels; the production of Crl was slightly greater at 28°C than at 37°C, whereas the σS levels were about twofold lower at 28°C than at 37°C. At both temperatures, Crl was present in excess of σS, and increasing the Crl level further did not increase the H2O2 resistance level of Salmonella and the expression of the σS-dependent gene katE encoding the stationary-phase catalase. In contrast, increasing the σS level rendered Salmonella more resistant to H2O2 at 28°C, increased the expression of katE, and reduced the magnitude of Crl activation. In addition, the effect of Crl on katE transcription in vitro was not dependent on temperature. These results suggest that the effect of temperature on Crl-dependent regulation of the katE gene and H2O2 resistance are mediated mainly via an effect on σS levels. In addition, our results revealed that σS exerts a negative effect on the production of Crl in stationary phase when the cells contain high levels of σS

Topics: Molecular Biology of Pathogens
Publisher: American Society for Microbiology (ASM)
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Provided by: PubMed Central
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