Environmental pH changes, but not the LuxS signalling pathway, regulate SpeB expression in M1 group A streptococci

J Med Microbiol. 2012 Jan;61(Pt 1):16-22. doi: 10.1099/jmm.0.036012-0. Epub 2011 Sep 2.


The autoinducer-2/LuxS signalling pathway participates in quorum sensing in diverse bacterial species. In group A streptococci (GAS), LuxS has been shown to be involved in regulating the expression of several important virulence factors. Streptococcal pyrogenic exotoxin B (SpeB), a cysteine protease that has important roles in GAS pathogenesis, is positively regulated by LuxS in M3 and M5 strains. In the present study, it was found that the supernatant harvested from an overnight culture stimulated M1 strains to express speB. However, mutation of the luxS gene in M1 strains or treating M1 strains with luxS mutant culture supernatant did not affect speB expression, indicating that the LuxS pathway is not involved in regulation of speB expression in M1 strains. In addition, the acid property of culture broth was found to be able to stimulate M1 strains to express speB in the same LuxS-independent manner. These results indicate that speB expression in M1 strains is induced by environmental pH changes but is not regulated by the LuxS signalling pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Carbon-Sulfur Lyases / genetics
  • Carbon-Sulfur Lyases / metabolism*
  • Culture Media / chemistry
  • Exotoxins / genetics
  • Exotoxins / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Humans
  • Hydrogen-Ion Concentration
  • Mutation
  • Signal Transduction
  • Streptococcus pyogenes / classification
  • Streptococcus pyogenes / genetics
  • Streptococcus pyogenes / metabolism*
  • Streptococcus pyogenes / physiology*
  • Virulence Factors


  • Bacterial Proteins
  • Culture Media
  • Exotoxins
  • Virulence Factors
  • erythrogenic toxin
  • Carbon-Sulfur Lyases
  • LuxS protein, Bacteria