Base ratio and deoxyribonucleic acid homology studies of six Staphylococcus aureus typing bacteriophages

Genetic relatedness among Staphylococcus aureus typing bacteriophages 80, 47, 81, 71, 77, and 187 was investigated by using base ratio determinations and deoxyribonucleic acid (DNA)-DNA hybridization. Guanine/cytosine (G/C) content, as determined by thermal denaturation and chromatographic analysis of the purines released by acid hydrolysis of the DNA, was between 31 and 36%. No pattern correlating G/C content with serological or lytic group was discernible. DNA-DNA hybridization studies indicated high degrees of homology (43% or more) among the genomes of phages in the same serological group. Less homology (29% or less) was observed between the genomes of phages belonging to different serological groups. These findings implied a positive correlation between serological and genetic relatedness.