Cross‐regulation of competence pheromone production and export in the early control of transformation in Streptococcus pneumoniae

作者：Bernard Martin, Marc Prudhomme, Geneviève Alloing, Chantal Granadel, Jean‐Pierre Claverys · 发表于：Molecular Microbiology · 年份：2000 · DOI：10.1046/j.1365-2958.2000.02187.x · 被引用次数：190 · 研究领域：Pneumonia and Respiratory Infections、Bacterial Infections and Vaccines、RNA and protein synthesis mechanisms

Two operons, comAB and comCDE, play a key role in the co-ordination of spontaneous competence development in cultures of Streptococcus pneumoniae. ComAB is required for export of the comC-encoded competence-stimulating peptide (CSP). Upon CSP binding, the histidine kinase ComD activates ComE, its cognate response regulator, required for autoinduction of comCDE and for induction of the late competence genes. To understand better the early control of competence development, mutants upregulating comCDE (ComCDEUP) were isolated using a comC-lacZ transcriptional fusion. Mutants were generated by polymerase chain reaction mutagenesis of the comCDE region and by in vitro transposon mutagenesis of the chromosome. Both types of ComCDEUP mutants exhibited similar phenotypes. They differed from wild type in displaying trypsin-resistant transformation, competence under acid growth conditions and expression of comCDE under microaerobiosis; increased production of CSP in the mutants could account for the various phenotypes. The ComCDEUP transposon mutations included four independent insertions in the ciaR gene, which encodes the response regulator of a two-component system previously found to affect competence, and two immediately upstream of the comAB operon. The latter two resulted in comAB overexpression, indicating that CSP export is rate limiting. Among comDE point mutations, a single amino acid change in ComD (T233I) conferred constitutive, CSP-independent competence and resulted in ...