nadB is essential for efficient intracellular replication of C. burnetii. Intracellular replication of C. burnetii NMII WT (closed circles), nadB::Tn 7-G9 (closed squares), nadB::Tn 7-G9 complemented strain (open squares), nadB::Tn 23-H5 (closed inverted triangles), and nadB::Tn 23-H5 complemented strain (open inverted triangles) was measured over 7 days. The fold increases in GEs relative to the inoculum were determined by ompA-specific qPCR and are represented here as the means ± S.D. of three independent infections at days 1, 3, 5, and 7 postinfection. Both nadB::Tn mutants were significantly reduced in growth compared with C. burnetii NMII at days 3, 5, and 7 (p < 0.05, paired t test).