RovA, a member of the MarR/SlyA family of winged-helix transcription factors, regulates expression of invasin, the major adhesion and invasion factor in Yersinia enterocolitica and Yersinia pseudotuberculosis. Disruption of rovA increases the LD(50) of the organism when inoculated using the oral route. However, when administered by intraperitoneal injection only a slight difference in LD(50) between mutant and wild-type organisms is apparent. The study of RovA and the genes it regulates provides a unique opportunity to gain insight into the initial stages of a Yersinia infection.