The Thermal Denaturation of Partly Purified Bacterial Deoxyribonucleic Acid and its Taxonomic Applications

Partly purified DNA and the corresponding highly purified DNA was obtained from 25 strains of Gram negative, rod‐shaped bacteria. The DNAs were examined by the thermal denaturation method and the melting temperatures of both partly and highly purified DNA samples from the same strain were in close agreement. For all strains, the mean difference in G+C contents estimated from the melting temperatures of each partly and highly purified DNA was 0.4% G+C. The presence of residual RNA and protein in the partly purified DNA samples contributed to variations in the total hyperchromism but did not significantly affect the accuracy of the melting temperature determination.