The major long-term objectives of the research of this laboratory are to define the chromosome of Staphylococcus aureus, and thus gain a better understanding of the factors that are responsible for pathogenicity, the manner by which extrachromosomal elements contribute to it's characteristics, and to evaluate the degree of diversity that exists within the genus Staphylococcus. The specific aims of this proposed research are to (1) continue with the characterization of the chromosome map of NCTC 8325 (phage group III) S. aureus, (2) continue to characterize the chromosome maps of strains 112 (phage group I) and Ps55 (phage group II), and their relationship to the NCTC 8325 map, (3) develop and evaluate potentially useful mutations that should expand the spectrum of useful approaches and flexibility of genetic analysis in S. aureus, (4) analyze the S. aureus chromosome for the presence of tandem genetic duplications from the perspective of using them as an aid in chromosome mapping, and (5) initiate the development of the necessary mapping techniques to develop genetic/physical chromosome maps of representative coagulase-negative staphylococci.//