DNA base composition, nature of intracellular DNA, morphology, and classification of bacteriophages infecting Micrococcus luteus

Ten bacteriophages infecting Micrococcus luteus have been characterized. All phages contain double-stranded DNA, of 64.3--73.5 mol% guanine plus cytosine (GC). The DNA of phage N7 has the highest GC content reported for any bacterial virus. No unusual bases have been found. The intracellular replicating DNAs of six phages are covalently closed circular molecules. All 10 phages have isometric, probably icosahedral, heads and long, flexible, noncontractile tails and can be sorted into two morphological groups based on size and presence or absence of a collar. Host-range studies indicate six host-range groups.