SUMMARY: Seven strains of viridans streptococci of the species and were investigated for autolysis. The effect of pH, salt concentration and temperature on the autolytic process was studied in NaHPO/NaHPO buffer. Whole cells and walls of all strains autolysed most rapidly at pH values above 7. Autolysis of whole cells of and one strain of (15909) was maximal in 0·05 to 0·2 buffer, while the two strains and 15912 showed maximal autolysis in 0·5 and 1·0 buffers. Cultures harvested in the stationary phase of growth possessed only slightly decreased autolytic activity compared with those from the exponential phase. Whole cells autolysed more rapidly at 37°C than at 45°C and 10°C. Autolysis of isolated walls of three strains of (903, 15909 and 15912) was maximal at pH 7.0 and 7·5 and in 1·0 buffers. 15909 also showed maximal lysis in 0·01 and 0·5 buffers. An endopeptidase action of the autolytic system of 15912 was indicated by the progressive release of soluble amino groups during autolysis of the walls. No release of reducing groups was observed. Several free amino acids were released during autolysis of these walls, alanine, lysine and glutamic acid being in greatest quantity.


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