BIOCHEMISTRY OF STAPHYLOCOCCAL EXOPOLYSACCHARIDES

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Certain strains of coagulase-positive (Staphylococcus aureus) and coagulase-negative (e.g., Staphylococcus epidermidis) staphylococci produce exopolysaccharides known as capsules and slimes. Capsules and slimes are morphologically and chemically distinct polymeric structures. Capsules are more firmly associated with the bacterial cell surface than slimes. Both capsules and slimes are virulence factors in that capsules allow strains to resist phagocytosis, and slimes promote adherence of staphylococci. Knowledge of the chemical structure of capsules, and slimes in particular, is at a relatively rudimentary stage. No in depth systematic studies on the physiology of capsule and slime production have been reported. Little information is available on the genetics and control of capsule and slime polysaccharides, or on the biological activities or host response to these polymers. This proposal is to open up the study of this area through study of the physiology and chemistry of staphylococcal capsules and slimes. The specific aims of the proposal are to: (i) employ optimal methods to isolate and purify capsular and slime polysaccharides; (ii) determine the chemical composition and structure of selected isolated and purified capsular and slime polysaccharides; (iii) examine the influence of the composition of the growth medium and cultural conditions on the production of capsular and slime polysaccharides to identify key components promoting polysaccharide production in selected staphylococcal strains.