[A study of the variability of group A type M29 streptococcus on exposure to biologically active substances].

Biologically active substances spermidine and the compounds contained in the low-molecular fraction of cattle blood serum change the phenotype of type 29 group A Streptococcus. Amino acid analysis and enzymatic destruction of cell walls have demonstrated changes of the streptococcal biological characteristics and cell wall structural organization. These changes may result from loss of supervariable component of the M-protein when compounds from cattle blood serum low-molecular fraction are added to culture medium and by unbalanced growth of Streptococcus after spermidine addition to growth medium.