BIOSYNTHESIS OF BACTERIAL CELL WALLS AND MEMBRANES

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We will study aspects of the biosynthesis and assembly of bacterial cell surface structures - the cell wall and membrane, in relationship to cellular growth and cell division. Streptococcus faecalis ATCC 9790 (S. faecium) will be used as a "model system", primarily because of its relatively simple shape and mode of division. Future investigations will emphasize: 1. The roles of the autolytic peptidoglycan hydrolase (an N-acetylmuramidase) in cell wall growth and division. The autolytic enzyme will be isolated, purified to homogeniety and a number of its properties will be studied. Interaction of highly purified enzyme with known inhibitors of its activity such as lipoteichoic acids and phospholipids will be studied. The kinetics of synthesis, and excretion of the lipoteichoic acid inhibitor will be studied during both balanced and unbalanced growth. 2. The isolation and study of the properties of conditional mutants with defects in cell wall or membrane assembly, structure, synthesis or function. Initial emphasis will be placed on mutants with defects in their autolytic enzyme system. 3. Detailed studies of observed variations in rates of peptidoglycan synthesis and capacity to autolyze of cells in various stages of the cell division cycle. We will be particularly interested in the biochemical and molecular mechanisms for regulation of autolytic activity during normal cell division. 4. Studies of the relationship of autolytic enzyme activity to the bactericidal action of penicillins and other antibiotics that inhibit cell wall assembly. The sequence of reactions leading to cell death will be investigated as will mechanisms by which streptomycin (and other aminoglycoside antibiotics) and penicillins (and other inhibitors of cell wall assembly) act synergistically.