A genetic analysis of Escherichia coli P6, a large-cell, radiation-resistant strain of E. coli, established that it originated as the result of a mutational event. The gene responsible for the complex P6 phenotype was located at 61 +/- 0.5 min on the E. coli linkage map. The close resemblance of conjugal and transductional recombinants to one or the other parent without indication of an interme...