| Abstract: | Lysogenic conversion has been suggested as a mechanism of control of group A streptococcal pyrogenic exotoxin type A production. Digestion of DNA from two converting bacteriophages, 3GL16 and T12, with a variety of restriction endonucleases yielded identical DNA fragments upon electrophoresis in agarose gels. Several known A toxin-positive strains that did not appear to produce converting phage upon induction were analyzed for toxin and phage DNA. Strains, including NY5, 594, and C203S, were shown by hybridization studies to carry the A toxin gene (speA) adjacent to chromosomally inserted phage fragments, homologous to phage T12 DNA, which may represent defective converting phages. The phage T12 att site mapped adjacent to speA. These data suggest that phage T12 acquired the A toxin gene from the bacterial genome. All streptococcal strains tested that were A toxin negative by Ouchterlony immunodiffusion failed to show any hybridization to speA-specific probes. |
