New types of Escherichia coli K-12 facultative recombination deficient mutants resistant to ultraviolet.

Numerous facultative temperature sensitive recombination deficient mutants of Escherichia coli K-12 strain 108 were isolated after mutagenization with nitrosoguanidine. The majority of the mutants were resistant to UV irradiation. Three mutants, KBP72, KBP169 and KBP610, with marked recombination deificiency (300 to 15,000 times) at 42 degrees C, were UV resistant; their sensitivity to mitomycin C was altered only slightly or not at all. Mutation KBP72 was co-transduced with ilv (83 unit on E. coli genetic map). The mutant is not able to form a functional recombinat structure. Two other mutations are located between 0 and 19 unit of the genetic map.