PCR and Western blot analysis of FTT0918. (A) PCR analysis of FTT0918 in different strains of F. tularensis. Lanes: 1, LVS2; 2, FSC688 (LVS2 cis complemented with pilA); 3, FSC693 (LVS2 cis complemented with FTT0918); 4, FSC694 (LVS2 cis complemented with pilA and FTT0918); 5, FSC200. An intact FTT0918 gene gives a PCR fragment of 4.4 kb, while the FTT0918 deletion gives a PCR fragment of 2.8 kb. (B) Expression of FTT0918 in different strains of F. tularensis analyzed by Western blotting using an anti-FTT0918 antiserum. Lanes: 1, LVS2; 2, FSC688 (LVS2 cis complemented with pilA); 3, FSC693 (LVS2 cis complemented with FTT0918); 4, FSC694 (LVS2 cis complemented with pilA and FTT0918); 5, FSC200; 6, FSC767 (FTT0918 insertion mutant of FSC200). The size of the intact FTT0918 protein is 58.8 kDa, the FTT0918-0919 fusion protein is 58.5 kDa, and the truncated FTT0918 protein is 42 kDa.