Complementation between uvr mutants of Streptococcus pyogenes

Summary From the group A streptococcal strains K 56 and 56 188, respectively 13 and 6 nitrosoguanidine-induced uvr mutants were isolated and used in complementation experiments employing strain 56 188 and its derivatives as donors in phage A 25-mediated heterologous transductions. When A 25 propagated on wild type or on 2 of the six 56 188-derived uvr mutants was used to infect 4 of the uvr recipient strains, a substantial increase in survivors of UV irradiation was found over those observed in selfing experiments or control experiments without phage. Less than 1% of the UV survivors had stably integrated the uvr⁺ allele. The remaining 4 uvr donors failed to complement the 4 above-mentioned recipients, indicating that the strains in question fell into 2 complementation groups.Nine of the 13 K 56-derived mutants, which in contrast to the others were characterized by non-reversibility to UV resistance, did not even show an increase in UV survivors when infected with phage grown on wild type. The possibility is discussed that these strains might carry second mutations affecting UV sensitivity which, however, did not appear to be of the rec type.