Abstract
By use of the staphylolytic enzyme lysostaphin, a method was devised for isolating and purifying highly polymerized deoxyribonucleic acid (DNA) from lysostaphinsusceptible Micrococcaceae. Staphylococcus aureus DNA isolated by this procedure gave an estimated molecular weight of ca. 2 x 10(8) and a residual protein content of 2.3%. The mole percentage of guanine + cytosine (GC) present in the DNA from 21 strains of aerobic Micrococceae was determined by buoyant density in cesium chloride. DNA from 12 biochemically typical members of the genus Staphylococcus gave a mean GC composition of 35.2 +/- 0.5 mole per cent. Four biochemically atypical Staphylococcus strains and one biochemically typical strain of the genus Micrococcus (M. candicans) were found to be susceptible to lysostaphin and gave typical Staphylococcus spp. GC base ratios. One biochemically atypical member of the genus Micrococcus (M. varians) was not susceptible to lysostaphin and gave a typical Micrococcus spp. GC base ratio. Lysostaphin susceptibility is an easy test to perform, and the results of this test appear to correlate with GC base ratio studies of the genera of Micrococcaceae.