The chemistry and biological significance of the reactions between penicillins and specific bacterial proteins will be examined. Attempts will be made to define the role of bound penicillin in the bactericidal effects of the penicillins and in the penicillinase-mediated resistance of certain microorganisms to these antibiotics. The penicillin binding characteristics and the enzymatic properties of the binding proteins from penicillinase inducible bacteria will be compared to those of penicillin sensitive microorganisms. Efforts will be made to determine if penicillin resistant bacteria (penicillinase-inducible) contain a separate, distinct penicillin binding component required for the induction of penicillinase.