Competence-specific autolysis in Streptococcus sanguis

Streptococcus sanguis strain Wicky activated to competence for genetic transformation is known to undergo a rapid decrease in optical density upon transfer to an alkaline buffer containing reducing agents. We studied the mechanism of this autolysis-like process and made the following observations. The process was specific because preincubation of the competence inducing factor with a specific inactivating protein prevented both cellular lysis and acquisition of competence for genetic transformation. The optical density decrease of competent bacteria involved the release of a large fraction of intracellular protein, RNA and lipid. However, no hydrolysis of phospholipid and no degradation of cell wall polymers including peptidoglycan could be detected. No peptidoglycan hydrolase activity capable of degrading radiolabelled S. sanguis cell walls was detected in unfractionated S. sanguis extracts. It is suggested that autolysis of competent S. sanguis involves the activity of a novel type of murein hydrolase that introduces only a limited number of bond breaks into the peptidoglycan.