Oral bacteria exist as compositionally and structurally complex populations in biofilms colonizing the tissues of the mouth. In most cases, oral biofilms are compatible with health. It is perturbations caused by environmental stresses that induce the changes in the composition and metabolic activities of biofilm bacteria that lead to the initiation and progression of oral diseases. The overall goals of the proposal are to provide detailed molecular and physiologic information about the capacity of oral bacteria to form and persist in biofilms, with particular focus on environmental stresses that can modulate the virulence of oral bacteria and enhance the pathogenic potential of oral biofilms. To achieve these goals, the following aims are outlined:
Aim 1. Analyze the molecular basis for post-transcriptional control of dnaK operon expression and stress tolerance in S. mutans.
Aim 2. Determine the role of (p)ppGpp in physiologic homeostasis, growth and survival decisions, and virulence expression in exponentially-growing S. mutans.
Aim 3. Dissect the molecular basis for stress tolerance and modulation of relP expression by a MarR transcriptional regulator and two ATP binding cassette exporters. By implementing the research plan, we will disclose fundamental details about the intimate linkage of stress tolerance with the ability of this organism to form biofilms on surfaces of the oral cavity. The research will provide the scientific community with an array of information that can be used to develop novel and more effective strategies to prevent and treat oral diseases and other debilitating human infectious diseases.

Public Health Relevance

The bacteria that cause oral diseases must be able to tolerate environmental stresses in the form of low pH, harmful oxygen radicals and deprivation for nutrients. The research conducted here examines the way in which bacteria regulate gene expression in response to their environment to optimize their ability to cause disease. Using state-of- the-art technologies, new targets for therapies to prevent or treat oral diseases and other infections in humans are being identified.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
Research Project (R01)
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Study Section
Oral, Dental and Craniofacial Sciences Study Section (ODCS)
Program Officer
Lunsford, Dwayne
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University of Florida
Schools of Dentistry
United States
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Seaton, K; Ahn, S-J; Burne, R A (2015) Regulation of competence and gene expression in Streptococcus mutans by the RcrR transcriptional regulator. Mol Oral Microbiol 30:147-59
Ahn, Sang-Joon; Kaspar, Justin; Kim, Jeong Nam et al. (2014) Discovery of novel peptides regulating competence development in Streptococcus mutans. J Bacteriol 196:3735-45
Guo, Qiang; Ahn, Sang-Joon; Kaspar, Justin et al. (2014) Growth phase and pH influence peptide signaling for competence development in Streptococcus mutans. J Bacteriol 196:227-36
Kim, Jeong Nam; Stanhope, Michael J; Burne, Robert A (2013) Core-gene-encoded peptide regulating virulence-associated traits in Streptococcus mutans. J Bacteriol 195:2912-20
Palmer, Sara R; Miller, James H; Abranches, Jacqueline et al. (2013) Phenotypic heterogeneity of genomically-diverse isolates of Streptococcus mutans. PLoS One 8:e61358
Kim, Jeong Nam; Ahn, Sang-Joon; Seaton, Kinda et al. (2012) Transcriptional organization and physiological contributions of the relQ operon of Streptococcus mutans. J Bacteriol 194:1968-78
Wen, Z T; Nguyen, A H; Bitoun, J P et al. (2011) Transcriptome analysis of LuxS-deficient Streptococcus mutans grown in biofilms. Mol Oral Microbiol 26:2-18
Seaton, Kinda; Ahn, Sang-Joon; Sagstetter, Ann M et al. (2011) A transcriptional regulator and ABC transporters link stress tolerance, (p)ppGpp, and genetic competence in Streptococcus mutans. J Bacteriol 193:862-74
Wen, Zezhang T; Yates, David; Ahn, Sang-Joon et al. (2010) Biofilm formation and virulence expression by Streptococcus mutans are altered when grown in dual-species model. BMC Microbiol 10:111
Ahn, Sang-Joon; Rice, Kelly C; Oleas, Janneth et al. (2010) The Streptococcus mutans Cid and Lrg systems modulate virulence traits in response to multiple environmental signals. Microbiology 156:3136-47

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