The cell wall is believed to play a major role in the expression of virulence of Streptococcus mutans. For example, cell surface interactions of S. mutans involving the wall are important for colonization on the tooth surface, adherence to other bacteria, reactions to host defense mechanisms, processing of carbohydrates and for genetic interactions. A thorough understanding of these activities will require detailed studies of the structure and location of all wall components and of those factors responsible for their synthesis and regulation. The main structural polymer of S. mutans cell walls is peptidoglycan and, although its composition has been well described, the factors affecting its physiological functions and activities remain to be determined. Peptidoglycan hydrolases are a major group of enzymes believed important in cell wall physiology. Normally, peptidoglycan hydrolases are important for the growth, division and wall chemistry of most bacteria. However, peptidoglycan hydrolyases are also capable of inducing massive lytic responses which result in the death of an organism. Similar lytic responses have been observed in S. mutans; however, the induction processes for this activity remains to be defined.
Our specific aims are to characterize peptidoglycan hydrolases of S. mutans SL-1 (serotype d) and to assess their physiological function and regulation. Crude peptidoglycan hydrolase preparations have been obtained by dilute-alkali extraction of whole S. mutans cells. The activities of the enzyme(s) will be assessed by enzymatic and chromatographic techniques. Characterization and physical properties of the enzyme will be determined by high pressure liquid chromatography following purification. Studies of regulation will include determining the nature of interactions of the enzyme with lipoteichoic acids, lysozyme, proteases, fluoride and other ions. The results from the proposed study will enhance our knowledge of the wall chemistry of S. mutans. They will also help to further our understanding of the complex interactions of the cell surface components with the environment. Finally, the potential for inducing lysis of S. mutans by the manipulation or deregulation of cell-wall associated enzymes, notably the peptidoglycan hydrolases, may also provide a new method for controlling populations of S. mutans and possibly other microorganisms.
