Peculiarities of the DNA of MM1, a temperate phage of Streptococcus pneumoniae.

The abundant presence of temperate phages in the chromosomes of clinical isolates of Streptococcus pneumoniae has been well documented. The genome of MM1, a temperate phage of pneumococcus, has been isolated as a DNA-protein complex. The protein is covalently bound to the DNA, was iodinated in vitro with Na125I, and has an Mr of 22,000. Electron microscopy and enzymatic analyses revealed that the MM1 genome is a linear, circularly permuted, terminally redundant collection of double-stranded DNA molecules packaged via a headful mechanism. The location of the pac site appears to be downstream of the terminase, between orf32 and orf34 of the MM1 genome.