Salmonella Research Today is a free monthly online journal that collates and summarizes the latest research about Salmonella, including details on salmonella typhimurium, food poisoning, infection, treatment. | ||||||||
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Effect of inactivation of degS on Salmonella enterica serovar typhimurium in vitro and in vivo.Rowley G, Stevenson A, Kormanec J, Roberts M Institute of Comparative Medicine, Professor of Molecular Bacteriology, Department of Veterinary Pathology, Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH, United Kingdom. m.roberts@vet.gla.ac.uk The alternative sigma factor (RpoE sigma(E)) enables Salmonella enterica serovar Typhimurium to adapt to stressful conditions, such as oxidative stress, nutrient deprivation, and growth in mammalian tissues. Infection of mice by Salmonella serovar Typhimurium also requires sigma(E). In Escherichia coli, activation of the sigma(E) pathway is dependent on proteolysis of the anti-sigma factor RseA and is initiated by DegS. DegS is also important in order for E. coli to cause extraintestinal infection in mice. We constructed a degS mutant of the serovar Typhimurium strain SL1344 and compared its behavior in vitro and in vivo with those of its wild-type (WT) parent and an isogenic rpoE mutant. Unlike E. coli degS strains, the Salmonella serovar Typhimurium degS strain grew as well as the WT strain at 42 degrees C. The degS mutant survived very poorly in murine macrophages in vitro and was highly attenuated compared with the WT strain for both the oral and parenteral routes of infection in mice. However, the degS mutant was not as attenuated as the serovar Typhimurium rpoE mutant: 100- to 1,000-fold more degS bacteria than rpoE bacteria were present in the livers and spleens of mice 24 h after intraperitoneal challenge. In most assays, the rpoE mutant was more severely affected than the degS mutant and a sigma(E)-dependent reporter gene was more active in the degS mutant than the rpoE strain. These findings indicate that degS is important for activation of the sigma(E) pathway in serovar Typhimurium but that alternative pathways for sigma(E) activation probably exist. Published 24 December 2004 in Infect Immun, 73(1): 459-63.
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