Physicochemical properties of temperate phage DNA and its possible effect on the variability of Mycobacterium lacticolum

The temperate phage 104 S was isolated from the S variant of Mycobacterium lacticolum, strain 104, and some of its characteristics were studied. The content of GC pairs in the phage DNA was 77 mole% as was calculated from the melting profile or 65 mole% as was calculated from the value of buoyant density in CsCl. The DNA was shown to be composed of 18,000 nucleotide pairs. DNA restriction fragments of M. lacticolum R, S and M variants were subjected for the first time to molecular hybridization with [32P]DNA of the temperate phage. The genome of the three M. lacticolum variants and the genome of a non-dissociating S variant clone were shown to contain sequences homologous to the DNA sequence of phage 104 S. Differences are found among the variants in the hybridizing DNA fragments. These data indicate that the phage DNA may actively be involved in the variability of the culture. Its participation can be realized by the different mode of prophage incorporation into the genome of the variants.