CONSTRUCTION OF A CHROMOSOME MAP FOR THE PHAGE GROUP-II STAPHYLOCOCCUS-AUREUS PS55

The genome size and a partial physical and genetic map have been defin ed for the phage group II Staphylococcus aureus Ps55. The genome size was estimated to be 2,771 kb by pulsed-field gel electrophoresis (PFGE ) using the restriction enzymes SmaI, CspI, and SgrAI. The Ps55 chromo some map was constructed by transduction of auxotrophic and cryptic tr ansposon insertions, with known genetic and physical locations in S, a ureus NCTC 8325, into the Ps55 background, PFGE and DNA hybridization analysis were used to detect the location of the transposon in Ps55. P s55 restriction fragments were then ordered on the basis of genetic co nservation between the two strains, Cloned DNA probes containing the l actose operon (lac) and genes encoding staphylococcal protein A (spa), gamma hemolysin (hlg), and coagulase (coa) were also located on the m ap by PFGE and hybridization analysis, This methodology enabled a dire ct comparison of chromosomal organization between NCTC 8325 and Ps55 s trains, The chromosome size, gene order, and some of the restriction s ites are conserved between the two phage group strains.