The aim of this research is to improve the understanding of a new cell surface regulatory process (Talk-Back regulation) in the """"""""Mutants"""""""" group of oral streptococci. The physiological aspects of this group of streptococci that enable them to survive the environmental stresses of """"""""feast or famine"""""""" and continuous assaults by host defense mechanisms inherent to the oral cavity, are basic to understanding the persistence and pathogenicity of these bacteria. Elucidation of the mechanism(s) by which the cell surface (in this instance, the Gram positive cell wall) communicates its growth status to the cytoplasm seems likely to be important to this regard. In addition to further describing a basic regulatory circuit, this study will also describe molecular events leading to the secondary inhibition of RNA and protein synthesis observed in the tolerant response to beta-lactam and other cell wall active antibiotics. This experimental approach will utilize established bacteriological and biochemical methods to analyze molecular events subsequent to exposure of growing bacterial cultures to benzylpenicillin and other inhibitors of cell wall synthesis. Analysis of putative regulatory nucleotides and stress proteins associated with the """"""""Talk- Back"""""""" response will be coupled with parallel studies on cultures undergoing other environmental stresses. Compositional and structural changes in the cell wall of bacteria subsequent to treatment with antibiotics will be performed via HPLC analysis of enzymatic digestion products. Appropriate regulatory mutants (to be isolated) will greatly facilitate the proposed research and provide the basis for future genetic analysis of the regulatory circuits of these streptococci. The long range objectives of this research are to define the molecular aspects of """"""""Talk-Back"""""""" regulation and the involvement of this pathway in the tolerant and nonlytic death responses to cell wall antibiotics and to improve the understanding of the basic physiology of the """"""""Mutants"""""""" streptococci which enable them to survive in an contribute to diseases of the oral cavity.
