citrulline ureidase is highly expressed in Francisella tularensis subsp. tularensis Schu S4 when compared to Francisella novicida U112, suggesting that it may contribute to the relative high virulence of Francisella tularensis subsp. tularensis Schu S4
generation of a nonpolar deletion DELTActu mutant. Deletion of the ctu gene results in loss of CTU activity, which is restored by transcomplementing the ctu gene. Loss of CTU does not affect acellular growth, but attenuates intramacrophage survival. Mice infected intranasally with the DELTActu mutant show significantly reduced bacterial burden in the lungs, liver, and spleen compared to wild-type Schu S4-infected mice.