PROTEIN ANTIMICROBIAL BARRIERS TO BACTERIAL ADHESION

The ability of microorganisms to adhere to solid surfaces is a problem of high visibility and has been the focus of numerous investigations because these organisms can cause disease and food spoilage. During th e last several years, considerable attention has been focused on the d evelopment of food-grade antimicrobial barriers to adhesion in order t o inhibit the initial adhesion of microbial contaminants by applicatio n of an antimicrobial agent to the surface rather than trying to remov e these contaminants once they are adhered. The premise is that, if bo th the presence of the agent and its antimicrobial activity are mainta ined at the interface, sensitive bacterial cells or spores that attemp t to attach would be killed. Nisin has been used in foods as a direct additive to inhibit the growth of Gram-positive cells and spores. Simi larly, hen lysozyme is a commercially available antimicrobial protein that offers application in food processing systems, but the mode of ac tion of this enzyme differs from that of nisin. We have shown that nis in can adsorb to surfaces, maintain activity, and kill cells that have adhered. In addition, we have addressed questions relating to the sho rt- and long-term stability of adsorbed nisin, the degree to which imm obilized nisin can resist exchange with dissolved solution components, and the surface concentrations that are necessary to inhibit biofilm formation. More recently, we have focused on basic questions relating to molecular influences on antimicrobial activity at interfaces using synthetic mutants of bacteriophage T4 lysozyme and hen lysozyme in add ition to nisin.