Absence of type specific M antigen from group A streptococci grown in a chemically defined medium.

The growth of three serological types of group A streptococci in a peptideand protein-free medium was described (Mickelson, Bacteriol Proc., p. 75, 1963). The three strains of Streptococcus pyogenes, Richards (type 3), N19 (type 19), and S43 (type 6; Slade and Slamp, J. Exptl. Med. 102:291, 1955), after repeated subculturing in the synthetic medium (100 or more times), were each tested for the group-specific and type-specific antigens by the precipitin test (Swift, Wilson, and Lancefield, J. Exptl. Med. 78:127, 1943). This procedure was performed on three separate batches of cells for each culture. On each test, the group A antigen ("C" polysaccharide) was present, but the type-specific antigen (M-protein) was absent. The same strains grown on a chemically defined medium containing reduced ovalbumin showed no loss of M protein (Slade and Slamp, J. Exptl. Med. 102:291, 1955). The absence of M protein was of special interest, and indicated the need for peptides in the medium for synthesis of M protein by the group A streptococci. This explanation was suggested by the results of Fox (J. Biol. Chem. 236:166, 1961), who showed that nonproliferating cells of S. pyogenes were stimulated to synthesize M protein, streptolysin 0, and proteinase by the presence of peptides from enzyme-hydrolyzed casein. Another suggested example of a protein requirement for biosynthesis of microbial antigens is the loss of agglutinability of mutant leptospirae when grown in a synthetic medium (Stalheim and Wilson, personal communication). Streptococcal cells harvested from a chemically defined medium, in which there was luxuriant growth, lacked M protein, which indicated that the biosynthesis of certain microbial antigens is not an obligatory part of the growth process.