Competence regulation by oxygen in Streptococcus pneumoniae: involvement of ciaRH and comCDE

Mol Microbiol. 2000 May;36(3):688-96. doi: 10.1046/j.1365-2958.2000.01891.x.


Anaerobic aerotolerant Streptococcus pneumoniae modulates its genetic transformability and its virulence in response to the oxygen concentration. The activity of a single protein encoded by nox and showing NADH oxidase activity is involved in these adaptive responses to O2. Northern blot analysis of wild-type cultures grown under aerobic and microaerobic conditions indicated transcriptional control of comCDE by O2. An O2-independent mutant strain carrying the gain-of-function mutation comE38KE was isolated and its analysis showed that ComE is a key point in competence stimulation by O2. Plasmid insertion mutations in ciaRH revealed that this two component signal-transducing system negatively regulates comCDE transcription. The level of comCDE transcripts appears as a major control point in competence regulation by O2 and also by growth phase and cell density.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaerobiosis
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Gene Expression Regulation, Bacterial*
  • Genotype
  • Histidine Kinase
  • Multienzyme Complexes*
  • Mutagenesis
  • Oxygen / pharmacology
  • Phenotype
  • Point Mutation
  • Protein Kinases / genetics
  • Streptococcus pneumoniae / drug effects
  • Streptococcus pneumoniae / genetics
  • Streptococcus pneumoniae / physiology*
  • Transcription, Genetic
  • Transformation, Bacterial
  • Virulence


  • Bacterial Proteins
  • ComE protein, Streptococcus pneumoniae
  • Multienzyme Complexes
  • comC protein, Bacillus subtilis
  • Protein Kinases
  • Histidine Kinase
  • Oxygen