Chitin hydrolysis by Listeria spp., including L. monocytogenes

Listeria spp., including the food-borne pathogen Listeria monocytogenes, are ubiquitous microorganisms in the environment and thus are difficult to exclude from food processing plants. The factors that contribute to their multiplication and survival in nature are not well understood, but the ability to catabolize various carbohydrates is likely to be very important. One major source of carbon and nitrogen in nature is chitin, an insoluble linear beta-1,4-linked polymer of N-acetylglucosamine (GIcNAc). Chitin is found in cell walls of fungi and certain algae, in the cuticles of arthropods, and in shells and radulae of molluscs. In the present study, we demonstrated that L. monocytogenes and other Listeria spp. are able to hydrolyze alpha-chitin. The chitinolytic activity is repressed by the presence of glucose in the medium, suggesting that chitinolytic activity is subjected to catabolite repression. Activity is also regulated by temperature and is higher at 30 degrees C than at 37 degrees C. In L. monocytogenes EGD, chitin hydrolysis depends on genes encoding two chitinases, lmo0105 (chiB) and Imo1883 (chiA), but not on a gene encoding a putative chitin binding protein (Imo2467). The chiB and chiA genes are phylogenetically related to various well-characterized chitinases. The potential biological implications of chitinolytic activity of Listeria are discussed.