Thus, PdpC directly or indirectly plays a very critical role for the virulence of F. tularensis. To determine the bacterial burden in organs, spleens were isolated 5 days after infection with a dose of 3 × 102 CFU of LVS or the ΔpdpC mutant and 16 days after infection with 1 × 107 CFU of either strain. This evidence concerns the gene PDP1 and infection.