All-or-nothing character of DNA degradation in bacteria after ionizing radiation.

The response of single cells of Escherichia coli B(s-11) and 15JG151 to radiation-induced DNA degradation has been observed by autoradiography. For both cells it is concluded that the event which causes DNA degradation is of an all-or-nothing character. The unit which suffers degradation is not the whole cell, but each cell has between two and four such units. The results suggest that there is some resynthesis of degraded DNA. Evidence that this occurs is shown by examining the degradation of mass cultures of 15TAU/t3 and t7 below and above the permissive temperature for DNA synthesis. The results on the all-or-nothing character are in agreement with previous studies made by completely different techniques.