[Comparison of the physicochemical structure of DNA in Corynebacterium related to C. diphtheriae v. mitis,...

The hybridization of DNA of 19 C. diphtheriae v. mitis strains with DNA of 3H-labeled C. diphtheriae v. mitis strain C7(beta) tox+ resulted in revealing four homology levels: I (102-98%), II (78-68%), III (61-50%) and IV (42-25%). Homology levels I and II differed from one another on the level of species. In the hybridization of DNA of the same strains with DNA of 3H-labeled C. diphtheriae v. gravis (group II) strain 165(1) tox+ three homology levels were revealed; levels I and II differed from one another on the level of the genus. In the first and second series of the experiments the distribution of DNA of the above strains on these levels not always coincided. The genomes of C. diphtheriae v. mitis strains 7111 tox+ and 132 tox+ were shown to differ from those of both reference strains on the level of the genus. In strains C7(beta) tox+ and PW-8 tox+ Massachusetts the genetic similarity of their genomes on the level of species was disclosed. Among C. diphtheriae v. mitis and intermedius strains at least 5 homology levels were revealed; this fact suggests the presence of at least 5 bacterial species among them. The relationship of strains on the level of species within groups I and II of C. diphtheriae v. gravis was confirmed: DNA of the related strains belonging to the corresponding group were always to be found within the same homology level. Also confirmed was the fact that the strains of groups I and II, as well as strain C7(beta) tox+, differed on the level of species.(ABSTRACT TRUNCATED AT 250 WORDS)