Bacteriophage control of antiphagocytic determinants in group A streptococci.
At least two genes have been shown to be required for the expression of the antiphagocytic M protein molecule in group A streptococci. Evidence for phage involvement in the expression of M protein is that: (a) M- cultures of bacteria can be converted to the M+ state (resistant to phagocytosis) upon lysogenization with appropriate bacteriophages; (b) without those bacteriophages the M- recipient culture could not be detected to revert to the M+ state, even under our most stringent selective conditions; and (c) stable M+ lysogens cured of their bacteriophages returned to the M- state. Immunochemical analysis of lysogenically converted M+ strains demonstrated that they contain precipitating and antiphagocytic determinants of the parental M-76 strain (CS110) rather than M-12 determinants expressed by the phage donor strain. This information strongly suggests that the M- strain CS112 possesses the structural gene for M protein, but that it remains predominantly unexpressed. Quantitation of the M antigen produced by these strains supports the observation that the M- phage-recipient strain possesses a small amount of extractable M antigen and that phage activates its synthesis by some unknown mechanism. Various possibilities to account for the phage requirement in M protein synthesis and its role in the transition between M+ and M- states are discussed.
D000954:Antigens, Surface / Q000235:genetics*; D001434:Bacteriophage Typing; D001435:Bacteriophages / Q000502:physiology*; D000939:Epitopes / Q000235:genetics*; D014644:Genetic Variation; D008242:Lysogeny; D010587:Phagocytosis; D013297:Streptococcus pyogenes / Q000235:genetics*
D000954:Antigens, Surface; D000939:Epitopes