Natural competence for genetic transformation in Streptococcus pneumoniae is controlled by the ComCDE signal-transduction pathway. Together, ComD, a membrane histidine kinase, and ComE, its cognate response regulator, constitute a typical two-component regulatory system involved in sensing the comC-encoded competence-stimulating peptide (CSP). The comCDE operon is strongly upregulated when CSP reaches a critical threshold, probably to coordinate competence induction throughout the population. During a study of the early regulation of the comCDE operon, a mutation which resulted in increased β-galactosidase production from a comC : : lacZ fusion was isolated. This mutation, which was characterized as a G→T change in the transcription terminator of the tRNAArg located immediately upstream of comCDE, is suggested to destabilize the terminator and to allow transcriptional readthrough of comCDE. Here, it is shown that, quite unexpectedly, the mutation confers reduced transformability. A series of experiments undertaken with the aim of understanding this surprising phenotype is described. Evidence is presented that increased basal-level expression of comDE impedes both spontaneous and CSP-induced competence in S. pneumoniae. There is a discussion of how an increased concentration of ComD and/or ComE could affect competence development.
AlloingG, GranadelC, MorrisonD. A, ClaverysJ. P.
1996; Competence pheromone, oligopeptide permease and induction of competence in Streptococcus pneumoniae . Mol Microbiol 21:471–478[CrossRef]
AlloingG, MartinB, GranadelC, ClaverysJ. P.
1998; Development of competence in Streptococcus pneumoniae : pheromone auto-induction and control of quorum-sensing by the oligopeptide permease. Mol Microbiol 29:75–84[CrossRef]
BergéM,
MoscosoM,
PrudhommeM,
MartinB.,
ClaverysJ. P.
2002; Uptake of transforming DNA in Gram-positive bacteria: a view from Streptococcus pneumoniae . Mol Microbiol 45:411–421[CrossRef]
ChastanetA, PrudhommeM, ClaverysJ. P, MsadekT.
2001; Regulation of Streptococcus pneumoniae clp genes and their role in competence development and stress survival. J Bacteriol 183:7295–7307[CrossRef]
ClaverysJ. P, HåvarsteinL. S. 2002; Extra-cellular peptide control of competence for genetic transformation in Streptococcus pneumoniae . Front Biosci 7:1798–1814[CrossRef]
GuiralS.
2004Libération de pneumolysine lors de la compétence pour la transformation génétique de la bactérie Streptococcus pneumoniae: implication d'une bactériocine à deux peptides PhD dissertation Université Paul Sabatier;
GuiralS, MitchellT. J, MartinB, ClaverysJ. P.
2005; Competence-programmed predation of noncompetent cells in the human pathogen Streptococcus pneumoniae : genetic requirements. Proc Natl Acad Sci U S A 102:8710–8715[CrossRef]
GuiralS, DagkessamanskaiaA, MoscosoM,
ClaverysJ. P.
2006a; Competence in Streptococcus pneumoniae : what is it for?. In The Molecular Biology of Streptococci Edited by HakenbeckR.,
ChhatwalG. S.
Norwich, UK: Horizon Scientific Press;
GuiralS, GranadelC, PrudhommeM, MartinB, ClaverysJ. P,
HénardV,
LaaberkiM.-H. 2006b; Construction and evaluation of a chromosomal expression platform (CEP) for ectopic, maltose-driven gene expression in Streptococcus pneumoniae . Microbiology 152:343–349[CrossRef]
HåvarsteinL. S,
CoomaraswamyG.,
MorrisonD. A.
1995; An unmodified heptadecapeptide pheromone induces competence for genetic transformation in Streptococcus pneumoniae . Proc Natl Acad Sci U S A 92:11140–11144[CrossRef]
HuiF. M, MorrisonD. A.
1991; Genetic transformation in Streptococcus pneumoniae : nucleotide sequence analysis shows comA , a gene required for competence induction, to be a member of the bacterial ATP-dependent transport protein family. J Bacteriol 173:372–381
HuiF. M, ZhouL, MorrisonD. A.
1995; Competence for genetic transformation in Streptococcus pneumoniae : organization of a regulatory locus with homology to two lactococcin A secretion genes. Gene 153:25–31[CrossRef]
LeeM. S, MorrisonD. A.
1999; Identification of a new regulator in Streptococcus pneumoniae linking quorum sensing to competence for genetic transformation. J Bacteriol 181:5004–5016
LuoP, LiH, MorrisonD. A.
2004; Identification of ComW as a new component in the regulation of genetic transformation in Streptococcus pneumoniae . Mol Microbiol 54:172–183[CrossRef]
MartinB, PratsH, ClaverysJ. P.
1985; Cloning of the hexA mismatch repair of Streptococcus pneumoniae and identification of the product. Gene 34:293–303[CrossRef]
MartinB,
GarcíaP,
CastaniéM. P,
ClaverysJ. P. 1995; The recA gene of Streptococcus pneumoniae is part of a competence-induced operon and controls lysogenic induction. Mol Microbiol 15:367–379[CrossRef]
MartinB, PrudhommeM, AlloingG, GranadelC, ClaverysJ. P.
2000; Cross-regulation of competence pheromone production and export in the early control of transformation in Streptococcus pneumoniae . Mol Microbiol 38:867–878[CrossRef]
Mortier-BarrièreI,
de SaizieuA,
ClaverysJ. P, MartinB.
1998; Competence-specific induction of recA is required for full recombination proficiency during transformation in Streptococcus pneumoniae . Mol Microbiol 27:159–170[CrossRef]
PestovaE. V, HåvarsteinL. S,
MorrisonD. A. 1996; Regulation of competence for genetic transformation in Streptococcus pneumoniae by an auto-induced peptide pheromone and a two-component regulatory system. Mol Microbiol 21:853–864[CrossRef]
PrudhommeM, ClaverysJ. P.
2006; There will be a light: the use of luc transcriptional fusions in living pneumococcal cells. In The Molecular Biology of Streptococci Edited by HakenbeckR.,
ChhatwalG. S.
Norwich, UK: Horizon Scientific Press;
SungC. K, MorrisonD. A.
2005; Two distinct functions of ComW in stabilization and activation of the alternative sigma factor ComX in Streptococcus pneumoniae . J Bacteriol 187:3052–3061[CrossRef]
SungC. K, LiH, ClaverysJ. P, MorrisonD. A.
2001; An rpsL cassette, janus, for gene replacement through negative selection in Streptococcus pneumoniae . Appl Environ Microbiol 67:5190–5196[CrossRef]
SuretteM. G, LevitM, LiuY, LukatG, NinfaE. G, NinfaA, StockJ. B.
1996; Dimerization is required for the activity of the protein histidine kinase CheA that mediates signal transduction in bacterial chemotaxis. J Biol Chem 271:939–945[CrossRef]
WeenO, GaustadP, HåvarsteinL. S. 1999; Identification of DNA binding sites for ComE, a key regulator of natural competence in Streptococcus pneumoniae . Mol Microbiol 33:817–827[CrossRef]