Adaptation of an osmotically fragile L-form of Streptococcus pyogenes to physiological osmotic conditions and its ability to destroy human heart cells in tissue culture.

An osmotically fragile L-form of Streptococcus pyogenes, type 12, was quickly rendered osmotically stable by decreasing the sodium chloride content of the growth medium and with the temporary use of oleic acid. The change from osmotic fragility to stability was accompanied by changes in cell yield, generation time, saturated/unsaturated fatty acid ratio of the membrane, and cytoplasmic protein composition. Finally, this resulting osmotically stable L-form survived and was capable of rapidly destroying Girardi human heart cells in tissue culture.