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Mol Microbiol. 2000 May;36(3):688-96.

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

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1
Laboratoire de Genétique et Physiologie Bactérienne, Centre Hospitalo Universitaire de Rangueil, Université Paul Sabatier 31403 Toulouse cedex, France.

Abstract

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.

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