title: Salmonella enteritidis has a homologue of tolC that is required for virulence in BALB/c mice.
abstract: The ability of Salmonella to invade tissue culture cells is correlated with virulence. Therefore, the tissue culture invasion model has been used extensively to study this process and to identify the bacterial genes involved and their products. Described here is the further characterization of a Salmonella enteritidis mutant (SM6T) originally identified as a non-invasive for tissue culture cells. A chromosomal DNA fragment complementing this defect was cloned and sequenced. The derived protein sequence is 89% identical to TolC from Escherichia coli, an outer membrane protein required for the signal peptide-independent transport of alpha-haemolysin and colicin V. Therefore, sinA was renamed tolC and is referred to in this text as tolCs to distinguish it from tolC of E. coli. TolCs and TolC are functionally similar since tolC can complement the invasion-defective phenotype of a tolCs mutant, and tolCs is required for export of alpha-haemolysin by Salmonella. The tolCs mutant is avirulent for mice when administered by the oral route, suggesting that the gene is important for virulence. Further characterization of the tolCs mutant indicated that like tolC mutants it is more sensitive than the wild-type strain to various detergents, antibiotics and dyes. This mutant is more sensitive to Triton X-100 only when associated with the monolayer, and the invasion-defective phenotype appears to be artifact of this sensitivity. In addition, the tolCs mutant is more sensitive to the bactericidal activity of human serum. Therefore, the avirulent phenotype could be the result of an inability to secrete a necessary virulence factor, or an increased sensitivity to complement and detergents as a result of a subtle alteration in the lipopolysaccharide (LPS) associated with tolC mutations.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Stone
authors.forename: V L
authors.initials: VL
authors.lastname: Miller
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003902:Detergents / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D029968:Escherichia coli Proteins; D005260:Female; D005816:Genetic Complementation Test; D006460:Hemolysin Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D012477:Salmonella enteritidis / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014774:Virulence / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003902:Detergents; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; D026901:Membrane Transport Proteins; C073126:tolC protein, E coli