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Journal of Bacteriology, January 2006, p. 399-408, Vol. 188, No. 2
0021-9193/06/$08.00+0 doi:10.1128/JB.188.2.399-408.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Regulation of SpeB in Streptococcus pyogenes by pH and NaCl: a Model for In Vivo Gene Expression
Jennifer A. Loughman and
Michael Caparon*
Department of Molecular Microbiology, Washington University School of Medicine, Box 8230, St. Louis, Missouri 63110-1093
Received 1 September 2005/
Accepted 24 October 2005
For a pathogen such as Streptococcus pyogenes, ecological success is determined by its ability to sense the environment and mount an appropriate adaptive transcriptional response. Thus, determining conditions for analyses of gene expression in vitro that are representative of the in vivo environment is critical for understanding the contributions of transcriptional response pathways to pathogenesis. In this study, we determined that the gene encoding the SpeB cysteine protease is up-regulated over the course of infection in a murine soft-tissue model. Conditions were identified, including growth phase, acidic pH, and an NaCl concentration of <0.1 M, that were required for expression of speB in vitro. Analysis of global expression profiles in response to these conditions in vitro identified a set of coregulated genes whose expression patterns showed a significant correlation with that of speB when examined during infection of murine soft tissues. This analysis revealed that a culture medium that promotes high levels of SpeB expression in vitro produced an expression profile that showed significant correlation to the profile observed in vivo. Taken together, these studies establish culture conditions that mimic in vivo expression patterns; that growth phase, pH, and NaCl may mimic relevant cues sensed by S. pyogenes during infection; and that identification of other environmental cues that alter expression of speB in vitro may provide insight into the signals that direct global patterns of gene expression in vivo.
* Corresponding author. Mailing address: Department of Molecular Microbiology, Washington University School of Medicine, Box 8230, St. Louis, MO 63110-1093. Phone: (314) 362-1485. Fax: (314) 362-3203. E-mail:
caparon{at}borcim.wustl.edu.
Supplemental material for this article may be found at http://jb.asm.org/.
Journal of Bacteriology, January 2006, p. 399-408, Vol. 188, No. 2
0021-9193/06/$08.00+0 doi:10.1128/JB.188.2.399-408.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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