Comparative genomics of Listeria species

Listeria monocytogenes is a food-borne pathogen with a high mortality rate that has also emerged as a paradigm for intraceitular parasitism. We presen t and compare the genome sequences of L. monocytogenes (2,944,528 base pair s) and a nonpathogenic species, L. innocua (3,011,209 base pairs). We found a large number of predicted genes encoding surface and secreted proteins, transporters, and transcriptional regulators, consistent with the ability o f both species to adapt to diverse environments. The presence of 270 L. mon ocytogenes and 149 L. innocua strain-specific genes (clustered in 100 and 6 3 islets, respectively) suggests that virulence in Listeria results from mu ltiple gene acquisition and deletion events.