This Article Full Text (PDF) Other Versions of this Article: JB.00813-07v1 189/18/6532    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Regev-Yochay, G. Articles by Malley, R. Search for Related Content PubMed PubMed Citation Articles by Regev-Yochay, G. Articles by Malley, R.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.00813-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

SpxB is a suicide gene of Streptococcus pneumoniae and confers a selective advantage in a competitive colonization in vivo model

Department of Epidemiology and Department of Immunology and Infectious Diseases, Harvard School of Public Health, and Division of Infectious Diseases, Department of Medicine, Children's Hospital, Harvard Medical School, Boston, MA

^* To whom correspondence should be addressed. Email: gregev{at}hsph.harvard.edu.

	Abstract

The human bacterial pathogen Streptococcus pneumoniae dies spontaneously when reaching stationary phase. The extent of S. pneumoniae death at stationary phase is unusual in bacteria and has been conventionally attributed to autolysis by the LytA amidase. In this study we show that spontaneous pneumococcal death is due to hydrogen peroxide (H₂O₂), not LytA, and that the gene responsible for H₂O₂ production (spxB) also confers a survival advantage in colonization. Survival of S. pneumoniae in stationary phase was significantly prolonged by eliminating H₂O₂ in any of three different ways: chemically by supplementing the media with catalase, metabolically by growing the bacteria in anaerobic conditions, or genetically by assessing spxB mutants that do not produce H₂O₂. Likewise, addition of H₂O₂ to exponentially growing S. pneumoniae resulted in a similar death rate as cells in stationary phase. While lytA mutants do not lyse at stationary phase, they died at a similar rate to the wild type strain. Furthermore, we show that the death process induced by H₂O₂ has features of apoptosis, as evidenced by increased Annexin V staining, decreased DNA content, and appearance on transmission electron microscopy. Finally, in an in vivo rat model of competitive colonization, the presence of spxB conferred a selective advantage over the spxB mutant, suggesting an explanation for the persistence of this gene. We conclude that the suicide gene of pneumococcus is spxB, which induces an apoptotic-like death in pneumococcus and confers a selective advantage in nasopharyngeal co-colonization.

This article has been cited by other articles:

• Allegrucci, M., Sauer, K. (2008). Formation of Streptococcus pneumoniae Non-Phase-Variable Colony Variants Is Due to Increased Mutation Frequency Present under Biofilm Growth Conditions. J. Bacteriol. 190: 6330-6339 [Abstract] [Full Text]  
• Mai-Prochnow, A., Lucas-Elio, P., Egan, S., Thomas, T., Webb, J. S., Sanchez-Amat, A., Kjelleberg, S. (2008). Hydrogen Peroxide Linked to Lysine Oxidase Activity Facilitates Biofilm Differentiation and Dispersal in Several Gram-Negative Bacteria. J. Bacteriol. 190: 5493-5501 [Abstract] [Full Text]  
• Kreth, J., Zhang, Y., Herzberg, M. C. (2008). Streptococcal Antagonism in Oral Biofilms: Streptococcus sanguinis and Streptococcus gordonii Interference with Streptococcus mutans. J. Bacteriol. 190: 4632-4640 [Abstract] [Full Text]  
• Rice, K. C., Bayles, K. W. (2008). Molecular Control of Bacterial Death and Lysis. Microbiol. Mol. Biol. Rev. 72: 85-109 [Abstract] [Full Text]