Isolation of an R- M+ mutant of Yersinia enterocolitica serotype O:8 and its application in construction of rough mutants utilizing mini-Tn5 derivatives and lipopolysaccharide-specific phage.

A generally applicable procedure was used to isolate a spontaneous restriction-deficient mutant of Yersinia enterocolitica serotype O:8. Transposition frequency in the mutant strain 8081-res was approximately 6.7 x 10(-6) per recipient, while it was practically zero in the wild-type strain 8081-c. Mobilization frequency into 8081-res was 10(5) times higher than that into the wild-type strain. The mutant had lost the ability to express the YenI restriction endonuclease activity present in serotype O:8 strains. This allowed the construction of a transposon library in 8081-res. Insertion mutants with transposons in the genes of the rfa region were selected from this library.