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Infect. Immun. doi:10.1128/IAI.01775-05
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The blp bacteriocins of Streptococcus pneumoniae mediate intraspecies competition both in vitro and in vivo

Departments of Microbiology and Pediatrics, University of Pennsylvania School of Medicine, Philadelphia; Division of Infectious Diseases, Children's Hospital of Philadelphia, Philadelphia PA

^* To whom correspondence should be addressed. Email: weiser{at}mail.med.upenn.edu.

	Abstract

The introduction of the seven-valent pneumococcal vaccine has led to the replacement of vaccine-serotypes with non-vaccine serotypes of Streptococcus pneumoniae. This observation implies that intraspecies competition between pneumococci occurs during nasopharyngeal colonization allowing one strain or set of strains to predominate over others. We investigated the contribution of the blp locus encoding putative bacteriocins and cognate immunity peptides to intraspecies competition. We sequenced the relevant regions of the blp locus of a type 6A strain able to inhibit the growth of TIGR4 in vitro. Using deletional analysis, we confirmed that inhibitory activity is regulated by the function of the response regulator, BlpR, and requires the two putative bacteriocin genes, blpM and blpN. Comparison of the TIGR4 BlpM and N amino acid sequences demonstrated that only five amino acid differences were sufficient to target the heterologous strain. Analysis of a number of clinical isolates suggests that the BlpMN bacteriocin divide into two families. A mutant in the blpMN operon created in the clinically relevant type 19A background was deficient in both bacteriocin activity as well as immunity. This strain was unable to compete with both its parent strain and a serotype 4 isolate during co-colonization in the mouse nasopharynx suggesting that the locus is functional in vivo and confirming its role in promoting intraspecies competition.

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