Competence-induced fratricide in streptococci

Authors

  • Jean-Pierre Claverys,

    Corresponding author
    1. Laboratoire de Microbiologie et Génétique Moléculaires, UMR5100 CNRS-Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 09, France.
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  • Bernard Martin,

    1. Laboratoire de Microbiologie et Génétique Moléculaires, UMR5100 CNRS-Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 09, France.
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  • Leiv Sigve Håvarstein

    1. Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway.
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E-mail claverys@ibcg.biotoul.fr; Tel. (+33) 561 33 59 11; Fax (+33) 561 33 58 61.

Summary

Competence for natural genetic transformation in Streptococcus pneumoniae is controlled by the extracellular concentration of the competence-stimulating peptide (CSP), an exported peptide pheromone. Upon entering the competent state, pneumococci start transcribing a number of CSP-responsive genes, termed the early and late competence (com) genes. Some of the proteins encoded by these com genes are absolutely required for DNA uptake and transformation, but most of them are dispensable. This finding indicates that the majority of CSP-regulated proteins in S. pneumoniae is involved in processes unrelated to natural genetic transformation. Recently, however, it became clear that the biological role of a few of the dispensable proteins might be linked to the transformation process. Although these proteins are not needed for transformation per se, they constitute a killing mechanism that could be used by competent cells to acquire DNA from non-competent pneumococci. This mechanism, termed fratricide, has so far only been described for pneumococci. In this manuscript, we review evidence that suggests the conservation of fratricide as well as the independent evolution of its genetic control and of its effectors in several species of the genus Streptococcus, and discuss its possible biological significance in relation to natural transformation.

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