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Infection and Immunity, January 2005, p. 459-463, Vol. 73, No. 1
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.1.459-463.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Effect of Inactivation of degS on Salmonella enterica Serovar Typhimurium In Vitro and In Vivo

Gary Rowley,1 Andrew Stevenson,1 Jan Kormanec,2 and Mark Roberts1*

Molecular Bacteriology Group, Institute of Comparative Medicine, Department of Veterinary Pathology, Glasgow University Veterinary School, Glasgow, United Kingdom,1 Institute of Molecular Biology, Centre of Excellence for Molecular Medicine, Slovak Academy of Science, Dubravska, Bratislava, Slovak Republic2

Received 4 June 2004/ Returned for modification 8 July 2004/ Accepted 17 September 2004

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°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.

* Corresponding author. Mailing address: Institute of Comparative Medicine, Professor of Molecular Bacteriology, Department of Veterinary Pathology, Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH, United Kingdom. Phone: 0141 330 5780. Fax: 0141 330 5602. E-mail: m.roberts{at}vet.gla.ac.uk.

Editor: J. T. Barbieri

Infection and Immunity, January 2005, p. 459-463, Vol. 73, No. 1
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.1.459-463.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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