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Journal of Bacteriology, December 2009, p. 7353-7362, Vol. 191, No. 23
0021-9193/09/$08.00+0     doi:10.1128/JB.01053-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Multiple Two-Component Systems Modulate Alkali Generation in Streptococcus gordonii in Response to Environmental Stresses{triangledown}

Yaling Liu and Robert A. Burne*

Department of Oral Biology, University of Florida, Gainesville, Florida 32610

Received 10 August 2009/ Accepted 16 September 2009

The oral commensal Streptococcus gordonii must adapt to constantly fluctuating and often hostile environmental conditions to persist in the oral cavity. The arginine deiminase system (ADS) of S. gordonii enables cells to produce, ornithine, ammonia, CO2, and ATP from arginine hydrolysis, augmenting the acid tolerance of the organism. The ADS genes are substrate inducible and sensitive to catabolite repression, mediated through ArcR and CcpA, respectively, but the system also requires low pH and anaerobic conditions for optimal activation. Here, we demonstrate that the CiaRH and ComDE two-component systems (TCS) are required for low-pH-dependent expression of ADS genes in S. gordonii. Further, the VicRK TCS is required for optimal ADS gene expression under anaerobic conditions and enhances the sensitivity of the operon to repression by oxygen. The known anaerobic activator of the ADS, Fnr-like protein (Flp), appeared to act independently of the Vic TCS. Mutants of S. gordonii lacking components of the CiaRH, ComDE, or VicRK grew more slowly in acidified media and were more sensitive to killing at lethal pH values and to agents that induce oxidative stress. This study provides the first evidence that TCS can regulate the ADS of bacteria in response to specific environmental signals and reveals some notable differences in the contribution of CiaRH, ComDE, and VicRK to viability and stress tolerance between the oral commensal S. gordonii and the oral pathogen Streptococcus mutans.

* Corresponding author. Mailing address: Department of Oral Biology, University of Florida, Gainesville, FL 32610. Phone: (352) 273-8850. Fax: (352) 273-8829. E-mail: rburne{at}dental.ufl.edu

{triangledown} Published ahead of print on 25 September 2009.

Journal of Bacteriology, December 2009, p. 7353-7362, Vol. 191, No. 23
0021-9193/09/$08.00+0     doi:10.1128/JB.01053-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Liu, Y., Burne, R. A. (2009). Multiple Two-Component Systems of Streptococcus mutans Regulate Agmatine Deiminase Gene Expression and Stress Tolerance. J. Bacteriol. 191: 7363-7366 [Abstract] [Full Text]  


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