Microarray-Based Identification of a Novel Streptococcus pneumoniae Regulon Controlled by an Autoinduced Peptide

Abstract

ABSTRACT We have identified in the Streptococcus pneumoniae genome sequence a two-component system (TCS13, Blp [bacteriocin-like peptide]) which is closely related to quorum-sensing systems regulating cell density-dependent phenotypes such as the development of genetic competence or the production of antimicrobial peptides in lactic acid bacteria. In this study we present evidence that TCS13 is a peptide-sensing system that controls a regulon including genes encoding Blps. Downstream of the Blp TCS (BlpH R) we identified open reading frames ( blpAB ) that have the potential to encode an ABC transporter that is homologous to the ComA/B export system for the competence-stimulating peptide ComC. The putative translation product of blpC , a small gene located downstream of blpAB , has a leader peptide with a Gly-Gly motif. This leader peptide is typical of precursors processed by this family of transporters. Microarray-based expression profiling showed that a synthetic oligopeptide corresponding to the processed form of BlpC (BlpC*) induces a distinct set of 16 genes. The changes in the expression profile elicited by synthetic BlpC* depend on BlpH since insertional inactivation of its corresponding gene abolishes differential gene induction. Comparison of the promoter regions of the blp genes disclosed a conserved sequence element formed by two imperfect direct repeats upstream of extended −10 promoter elements. We propose that BlpH is the sensor for BlpC* and the conserved sequence element is a recognition sequence for the BlpR response regulator.