Deoxyribonucleic acid homologies among some bacteria.

The deoxyribonucleic acid (DNA)-agar method has been employed to demonstrate homologies among the DNA's of several members of the Enterobacteriaceae (B. J. McCarthy and E. T. Bolton, Proc. Natl. Acad. Sci. U.S. 50:156,1963). This work used the extent of reaction (binding) of radiolabeled DNA fragments to a series of DNA-agars as the index of polynucleotide homology. Competition experiments, in which a large excess of unlabeled DNA fragments comshown in Table 1. Specificity of the technique was assured by control experiments in which the background binding of Escherichia coli B fragments and Salmonella typhimurium strain LT2 fragments to agar containing no DNA was 0.4 and 0.25%, respectively. In addition, DNA fragments from Brucella neotomae, an organism unrelated to the Enterobacteriaceae, were unable to compete with E. coli fragments for sites on E. coli DNA-agar (Table 1, bottom line).