A Phage-associated Murein Hydrolase in Streptococcus pneumoniae Infected with Bacteriophage Dp-1

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Abstract
A phage-associated murein hydrolase activity capable of degrading pneumococcal cell walls was isolated and purified to homogeneity from the phage-induced lysate of an autolysis-defective pneumococcal mutant infected with the bacteriophage Dp-1. Some properties of the enzyme resembled those of the wild-type (host) pneumococcal murein hydrolase; cell walls prepared from ethanolamine-grown pneumococci were resistant to the enzyme; the activity was inhibited by the Forssman antigen and was sensitive to proteolytic enzymes. The phage-associated enzyme was not inhibited by antiserum prepared against the purified pneumococcal murein hydrolase; the activity was stimulated by reducing agents and was partially inhibited by cardiolipin. The subunit MW of the phage-associated enzyme was somewhat smaller (31,000) than that of the pneumococcal hydrolase (35,000). This appears to be the first description of a phage-associated murein hydrolase activity in pneumococci.