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J. Bacteriol. doi:10.1128/JB.01144-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Regulation of gene expression in Streptococcus pneumoniae by response regulator 09 is Strain-Dependent

Department of Pediatrics, Erasmus MC-Sophia Children's Hospital, Rotterdam, The Netherlands.; Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, United Kingdom.; Laboratory of Pediatric Infectious Diseases, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.; Department of Molecular Genetics, University of Groningen, Haren, The Netherlands

^* To whom correspondence should be addressed. Email: P.Hermans{at}cukz.umcn.nl,

	Abstract

Recent murine studies have demonstrated that the role of response regulator 09 (RR09) of S. pneumoniae in virulence varies between strains. In the present study, we used a murine pneumonia model of infection to assess the virulence of a TIGR4 rr09-mutant, and found that TIGR4rr09 was attenuated after intranasal infection. Further, we investigated the in vitro transcriptional changes in pneumococcal rr09 mutants of two strains, D39 and TIGR4, by microarray analysis. The transcriptional profiles of the rr09 mutants in both strains displayed clear differences compared to their parental wild-type. In D39rr09 but not TIGR4rr09, genes involved in competence (e.g. comAB) were upregulated. In TIGR4, genes located on the rlrA pathogenicity islet, absent in the D39 genome, appeared to be regulated by RR09. Furthermore, several phosphotransferase systems (PTSs), believed to be involved in sugar uptake (e.g., sp0060-sp0066), were strongly downregulated in D39rr09, while not regulated by RR09 in TIGR4. To address the role of one of these PTS in virulence, D39sp0063 was constructed and tested in a murine infection model. No difference in virulence compared to the wild-type was found, indicating that downregulation of this gene alone is not the cause of the avirulent phenotype of D39rr09. Finally, expression of rr09 and three of our identified RR09 targets were assessed during infection in mice. This in vivo experiment confirmed differences in expression between TIGR4 wild-type and rr09-mutant, as well as between wild-type D39 and TIGR4. In conclusion, our results indicate strain-specific regulation of pneumococcal gene expression by RR09.

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