Competence-specific Autolysis in Streptococcus sanguis

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Abstract
S. sanguis strain Wicky activated to competence for genetic transformation undergoes a rapid decrease in optical density upon transfer to an alkaline buffer containing reducing agents. The mechanism of this autolysis-like process was studied. 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 phospolipid and no degradation of cell wall polymers, including peptidoglycan, could be detected. No peptidoglycan hydrolase activity capable of degrading radiolabeled S. sanguis cell walls was detected in unfractionated S. sanguis extracts. Autolysis of competent S. sanguis may involve the activity of a novel type of murein hydrolase that introduces only a limited number of bond breaks into the peptidoglycan.