Characteristics of a Lytic Enzyme Induced by Bacteriophage Infection of Micrococcus lysodeikticus

A lytic enzyme induced in Micrococcus lysodeikticus strain 1 by infection with N1 bacteriophage was purified 45- to 50-fold by ammonium sulfate precipitation, acid precipitation, and selective adsorption of contaminating proteins with calcium phosphate gel. The optimal pH for activity of the enzyme was 6.5 to 7.0. Maximal activity occurred at 45 to 50 C and at an ionic strength of 0.06. The enzyme had a limited specificity and lysed cell walls of M. lysodeikticus with the release of dinitrofluorobenzene reactive groups. Living cells were lysed in the absence of phage; however, the rate of lysis increased when phage was present in excess of 10 particles per bacterial cell. Young cells were most sensitive, and the sensitivity decreased to a minimum with stationary-phase cells. Acting synergistically, lysozyme and the N1-induced lysin caused lysis of cells which were resistant to either enzyme acting independently. The N1 lysin did not exhibit proteolytic activity.