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Infection and Immunity, December 2001, p. 7254-7261, Vol. 69, No. 12
Department of Infectious Diseases, Centre for
Molecular Microbiology and Infection, Imperial College School of
Medicine, London SW7 2AZ, United Kingdom
Received 1 June 2001/Returned for modification 18 July
2001/Accepted 19 September 2001
Many virulence factors are required for Salmonella
enterica serovar Typhimurium to replicate intracellularly and
proliferate systemically within mice. In this work, we have carried out
genetic analyses in vivo to determine the functional relationship
between two major virulence factors necessary for systemic infection by S. enterica serovar Typhimurium: the
Salmonella pathogenicity island 2 (SPI-2) type III
secretion system (TTSS) and the PhoP-PhoQ two-component regulatory
system. Although previous work suggested that PhoP-PhoQ regulates SPI-2
TTSS gene expression in vitro, in vivo competitive analysis of mutant
strains indicates that these systems contribute independently to
S. typhimurium virulence. Our results also suggest that
mutation of phoP may compensate partially for defects in
the SPI-2 TTSS by deregulating SPI-1 TTSS expression. These results
provide an explanation for previous reports showing an apparent
functional overlap between these two systems in vitro.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.12.7254-7261.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
In Vivo Genetic Analysis Indicates That PhoP-PhoQ
and the Salmonella Pathogenicity Island 2 Type III
Secretion System Contribute Independently to Salmonella
enterica Serovar Typhimurium Virulence
*
Corresponding author. Mailing address: Department of
Infectious Diseases, Centre for Molecular Microbiology and Infection, Imperial College School of Medicine, Armstrong Rd., London SW7 2AZ,
United Kingdom. Phone: 44-(0)20-7594-3073. Fax: 44-(0)20-7594-3076. E-mail: d.holden{at}ic.ac.uk.
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