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A two-component regulatory system (phoP phoQ) controls Salmonella typhimurium virulence
S I Miller1, A M Kukral, J J Mekalanos
1Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115.
Summary
Mutations in the Salmonella typhimurium phoP locus significantly reduce virulence in mice. These phoP and phoQ genes are key regulators, and their disruption offers partial protection against wild-type Salmonella infection.
Area of Science:
- Microbiology
- Genetics
- Immunology
Background:
- Salmonella typhimurium is a significant pathogen.
- Virulence factors are crucial for bacterial pathogenesis.
- Two-component regulatory systems control bacterial responses to environmental cues.
Purpose of the Study:
- To investigate the role of the phoP locus in Salmonella typhimurium virulence.
- To characterize the phoP and phoQ genes and their regulatory functions.
- To evaluate the potential of phoP/phoQ mutants as live vaccines.
Main Methods:
- Genetic manipulation of Salmonella typhimurium strains to create mutations in phoP, phoQ, and pagC.
- DNA sequencing to determine the genetic organization of the phoP locus.
- Virulence assays in BALB/c mice.
- Macrophage survival assays.
- Live vaccine efficacy studies.
Main Results:
- Mutations in the phoP locus (phoP, phoQ) markedly attenuated Salmonella typhimurium virulence in mice.
- The phoP locus comprises an operon of two genes, phoP and phoQ, encoding transcriptional regulators.
- Strains with phoP or phoQ mutations showed decreased survival in macrophages.
- A pagC mutation also resulted in a virulence defect.
- phoP/phoQ mutants provided partial protection against wild-type Salmonella challenge when used as live vaccines.
Conclusions:
- The Salmonella typhimurium phoP/phoQ two-component system is essential for virulence.
- Disruption of the phoP/phoQ regulon impairs bacterial survival in macrophages.
- phoP/phoQ mutants represent promising candidates for live attenuated Salmonella vaccines.