PMID:11679074

Citation	Lyon, WR, Madden, JC, Levin, JC, Stein, JL and Caparon, MG (2001) Mutation of luxS affects growth and virulence factor expression in Streptococcus pyogenes. Mol. Microbiol. 42:145-57
Abstract	Adaptive responses of bacteria that involve sensing the presence of other bacteria are often critical for proliferation and the expression of virulence characteristics. The autoinducer II (AI-2) pathway has recently been shown to be a mechanism for sensing other bacteria that is highly conserved among diverse bacterial species, including Gram-positive pathogens. However, a role for this pathway in the regulation of virulence factors in Gram-positive pathogens has yet to be established. In this study, we have inactivated luxS, an essential component of the AI-2 pathway, in the Gram-positive pathogen Streptococcus pyogenes. Analyses of the resulting mutants revealed the aberrant expression of several virulence properties that are regulated in response to growth phase, including enhanced haemolytic activity, and a dramatic reduction in the expression of secreted proteolytic activity. This latter defect was associated with a reduced ability to secrete and process the precursor of the cysteine protease (SpeB) as well as a difference in the timing of expression of the protease. Enhanced haemolytic activity of the luxS strain was also shown to be linked with an increased expression of the haemolysin S-associated gene sagA. Disruptions of luxS in these mutants also produced a media-dependent growth defect. Finally, an allelic replacement analysis of an S. pyogenes strain with a naturally occurring insertion of IS1239 in luxS suggested a mechanism for modulation of virulence during infection. Results from this study suggest that luxS makes an important contribution to the regulation of S. pyogenes virulence factors.
Links	PubMed
Keywords	Animals; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Carbon-Sulfur Lyases; Culture Media; Cysteine Endopeptidases/genetics; Cysteine Endopeptidases/metabolism; Fungal Proteins/genetics; Fungal Proteins/metabolism; Homoserine/analogs & derivatives; Homoserine/genetics; Homoserine/metabolism; Humans; Lactones/metabolism; Mutation; Streptococcus pyogenes/genetics; Streptococcus pyogenes/growth & development; Streptococcus pyogenes/pathogenicity; Streptococcus pyogenes/physiology; Streptolysins/metabolism; Transcription, Genetic; Virulence/genetics
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