Recombination deficient mutants of Streptococcus pyogenes K56

Abstract

Nitrosoguanidinc mutagenesis of the Group A streptococcal strain K56 known as a good recipient in phage-mediated transduction led to the isolation of two recombination deficient mutants showing transduction frequencies of chromosomal markers about 100-fold lower than those of the parent strain. These mutants were sensitive to ultraviolet (UV) irradiation hut had retained their ability t o reactivate UV-irradiated phage A25. They were cross-sensitive to the killing action of nitrosognanidine and ethyl methane sulfonate and showed severely inhibited DNA synthesis after UV radiation.

Recombination-deficient mutant of Streptococcus faecalis

“…The ability to revert suggests that the original lesion was a point mutation. The mutant resembles recA strains of Escherichia coli (1), which, like similar mutants in Haemophilus influenzae (14), Bacillus subtilis (17), Staphylococcus aureus (10,22), and S. pyogenes (15), are sensitive to UV irradiation and chemical agents which interact with DNA. Such strains also have been shown to undergo DNA degradation upon exposure to irradiation; UV202 also exhibited this trait.…”