Listeria monocytogenes is a facultative intracellular pathogen that causes listeriosis, a highly fatal food-borne infection. After entry into host cells, L. monocytogenes escapes from the phagocytic vacuole and replicates actively in the cytosol. Although the replication phase is essential for the establishment and survival of the pathogen within the host and its further transmission to new hosts, investigations into the microbial pathogenesis have largely neglected this phase of the infection process and therefore little is known about the nutritional determinants of microbial growth in vivo.