Maillard reaction causes suppression of virulence gene expression in Listeria monocytogenes

Many environmental signals affect the expression of virulence genes of the food borne pathogen Listeria monocytogenes. in addition media composition h as been shown to suppress levels of haemolytic activity. Using a Pr-plcA::l uxAB reporter gene fusion it was observed that the heat processing of media also reduces the level of virulence gene expression in L. monocytogenes wi thout affecting its growth. Physicochemical factors that are considered to enhance the Maillard reaction were also found to increase the levels of sup pression. The results indicate that heat treatment of a multicomponent matr ix gives rise to specific inhibitors of the Listeria virulence gene operon. (C) 2000 Elsevier Science B.V. All rights reserved.