Abstract
A diffusible inhibitor of bacterial growth (bacteriocine) was produced by 4 of 130 strains of Group A streptococci examined. Bacteriocine production on Todd Hewitt medium was optimal at pH 6.0-6.5. Partial purification suggests that the bacteriocine is of low molecular weight and is at least partly composed of protein. The bacteriocine was active against many strains of streptococci and other Gram-positive organisms but not against staphylococci or any of the Gram-negative strains examined.