Detection of homology to the beta bacteriophage integration site in a wide variety of Corynebacterium spp.

In toxigenic conversion of Corynebacterium diphtheriae C7, β bacteriophage DNA integrates into either of two chromosomal attachment sites, attB1 or attB2. These attB sites share a 96-base-pair sequence with the attP sites of β-related phages. The distribution of attB-related sites in other species of Corynebacterium was assessed by hybridization with a DNA probe containing both attB sites of the C7 strain and a second DNA probe containing the attP site of a β-related phage. All but one of the 15 C. diphtheriae strains tested, regardless of origin or colonial type, contained at least two BamHI fragments that hybridized strongly to both of these probes under conditions of high stringency. Strains of C. ulcerans and C. pseudotuberculosis, species in which conversion to toxinogeny has also been demonstrated, also had one or two hybridizing BamHI fragments. The functionality of these sites as integration sites was demonstrated by isolating lysogens of all three species following single infection with one or more β-related phages. As predicted, following lysogenization one of the DNA fragments that had exhibited homology with the attB1-attB2 probe was replaced by two hybiridizing fragments. Other species of Corynebacterium, including pathogens and nonpathogens from animals, plant pathogens, and soil isolates also carried at least one BamHI fragment that hybridized with the attB1-attB2 and attP probes. The data indicate that sequences homologous to the β phage integration sites in C. diphtheriae have been conserved in members of the genus Corynebacterium.