Interspecies Streptococcal Antagonisms in Oral Biofilms

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DESCRIPTION (provided by applicant): The Candidates background is in bacterial genetics, biofilm formation and bacterial virulence. The immediate goal is to prepare for a career as an independent scientist and to develop a model for bacterial interactions in the dental biofilm. The career objective is to become an independent scientist studying oral microbial ecology as ranked academic faculty. The mentored-phase will include the development of additional technical skills, topical, teaching and pedagogy, participation in the T32 MinnCResT program, and presenting in seminars and at conferences. The mentored phase will include establishment of interdisciplinary collaborations with researchers at UMN, which will be extended during the independent phase, when the main focus is the achievement of the proposed research. Environment: The proposed research will be performed at the School of Dentistry, UMN in the lab of Dr. M.C. Herzberg, a renowned expert in streptococcal biology especially in surface-adhesion proteins, biofilm development and the patho-physiology of S. sanguinis in endocarditis. Research: The role of S. mutans in the etiology of dental caries has been well investigated. S. mutans resides in the dental plaque with over 70 bacterial species. Indeed, interaction in the S. mutans-associated microbiome may determine the cariogenic potential of dental plaque. These interactions include modulation of gene expression, interspecies co-aggregation and growth inhibition. We hypothesize that oral streptococci compete in part by influencing virulence gene expression in the antagonized or challenged species by direct physical interactions and/or metabolic signaling. We will model interactions of S. mutans and S. sanguinis because their mutual exclusion in dental plaque is well-known. To test our hypothesis that interspecies interactions influence the outcome of the competition between S. mutans and S. sanguinis, we will: (a) Develop a dual-species biofilm model based on saliva coated hydroxyapatite; (b) Search for new genes involved in the interspecies interaction between S. mutans and S. sanguinis; (d) Determine the mutual influenced expression profile of S. mutans and S. sanguinis virulence genes; (c) Further characterize the direct physical interactions between S. mutans and S. sanguinis by atomic force microscopy. Relevance: Virulence factors will be characterized that specify inter-species competition in the oral biofilm, contributing to better understanding and control of the overgrowth of cariogenic S. mutans.