Recombination-deficient mutant of Salmonella typhimurium

A recombination-deficient (Rec(-)) ultraviolet-sensitive mutant of Salmonella typhimurium was isolated. The mutant grows more slowly than the wild-type strain and degrades its deoxyribonucleic acid extensively both during normal growth and after ultraviolet irradiation. Evidence is presented that a growing Rec(-) population consists of two types of cells, one which can divide and one which cannot.