Proc Natl Acad Sci U S A. 2005 Jun 14;102(24):8710-5. Epub 2005 May 31.

Competence-programmed predation of noncompetent cells in the human pathogen Streptococcus pneumoniae: genetic requirements.

Guiral S, Mitchell TJ, Martin B, Claverys JP.

Source

Laboratoire de Microbiologie et Génétique Moléculaires, Unité Mixte de Recherche 5100, Centre National de la Recherche Scientifique, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex, France.

Abstract

Natural competence for genetic transformation is the best-characterized feature of the major human pathogen Streptococcus pneumoniae. Recent studies have shown the virulence of competence-deficient mutants to be attenuated, but the nature of the connection between competence and virulence remained unknown. Here we document the release, triggered by competent cells, of virulence factors (e.g., the cytolytic toxin pneumolysin) from noncompetent cells. This phenomenon, which we name allolysis, involves a previously undescribed bacteriocin system consisting of a two-peptide bacteriocin, CibAB, and its immunity factor, CibC; the major autolysin, LytA, and lysozyme, LytC; and a proposed new amidase, CbpD. We show that CibAB are absolutely required for allolysis, whereas LytA and LytC can be supplied either by the competent cells or by the targeted cells. We propose that allolysis constitutes a competence-programmed mechanism of predation of noncompetent cells, which benefits to the competent cells and contributes to virulence by coordinating the release of virulence factors.