Effects of Lysozyme on Bacillus cereus 569: Rupture of Chains of Bacteria and Enhancement of Sensitivity to Autolysins

Bacillus cereus 569 is known to be resistant to lysis by lysozyme because of the presence of deacetylated glucosamine residues in its peptidoglycan, and cultures continued to grow even in the presence of lysozyme at 200 microgram ml-1. However, lysozyme caused rupture of the chains of bacteria and promoted the rate of autolysis in a non-growing cell suspension, causing a doubling of the rate of release of radioactively labelled wall material. Heat-inactivated cells did not autolyse and were not lysed by lysozyme unless they were supplemented by unheated cells or cell-free autolysate. Enhancement of autolysin activity could also be effected by pre-treatment of heated cells with lysozyme. The action of lysozyme on isolated cell walls released some free reducing groups, indicating limited breakage of the polysaccharide chains of peptidoglycan, and it was concluded that lysozyme modified the peptidoglycan and made it more susceptible to autolysin(s). Lysozyme also enhanced the rate of septum separation and the probable significance of the results in relation to the control of cell separation is discussed.