Thermal stability of homologous and heterologous bacterial DNA duplexes

Thermal stability of homologous and heterologous DNA duplexes renatured according to the renaturation-rate method of De Ley et al. (1970) for 35 min or 17 hr, was estimated from the melting profiles of the duplexes. Comparison of the melting points of native and renatured DNA revealed that in the first 35 min of renaturation highly stable homologous duplexes were mainly formed, whereas up to 7% mismatching occurred in duplexes renatured for 17 hr. Up to 8% more mismatching was found in heterologous DNA duplexes of moderately related coryneform bacteria than in homologous ones after 35 min renaturation. It can be concluded that mismatching in heterologous hybrids of closely related DNAs had been restricted to a few % and of moderately related DNAs to approximately 10% in the initial renaturation phase.