Listeria monocytogenes is a saprophytic food borne microorganism which is pathogenic to humans and animals. The pathogenicity and physiological features of L. monocytogenes have been studied for many years. Some characteristics of this microorganism have been described, such as its low temperature growth and adaptation, the expression of its flagellin gene, and the regulation of its virulence genes. Previous studies imply a possible reversed relationship that may exist between the regulation of the listerial flagellin gene, flaA and its virulence regulator gene, prfA.