Factors affecting the susceptibility of bacterial cell walls to the action of lysozyme

Abstract Although we have heard a lot about the mode of binding of low molecular weight, soluble, lysozyme substrates, we have heard little about the mode of action of lysozyme on its natural insoluble substrate, the bacterial cell wall; so I want to bring a biological flavour into this discussion. Lysozyme was the name given by Fleming (1922) to the powerful bacteriolytic agent found in various cells and secretions; it was particularly active against a new bacterial species which he named Micrococcus lysodeikticus. The walls of this species still provide us with one of the best substrates for the study of lysozyme action. Salton showed that there is a considerable spectrum of activity of lysozyme in solubilizing walls of other species of bacteria. For example, walls of M. lysodeikticus are attacked rapidly by a concentration of enzyme of 1 μg/ml., Bacillus megaterium walls need 50 μg/ml., while walls of B. cereus are hardly changed visibly by 50 μg/ml. Consideration of the structure of the basal mucopeptide unit of bacterial cell walls, illustrated by Dr Perkins, shows that there are many ways in which structural differences could be introduced. Knowledge of the effects of some of these differences on lysozyme sensitivity may help in elucidating the mode of action of lysozyme on the complete bacterial cell wall.