FIG. 1.

B. anthracis Sterne endospores require gerH for germination in macrophage cultures. (A) RAW 264.7 Mφ were infected with ⁴⁵Ca-radiolabeled B. anthracis Sterne 34F2 (black bars), the gerH-null strain carrying pKSV7:gerH (open bars), and gerH-null endospores (grey bars). (B) Germination experiments were performed with ⁴⁵Ca-radiolabeled 34F2 endospores in cultures of J774A.1 (grey bars) and RAW 264.7 (black bars) Mφ that were incubated in MEM with or without the addition of cytochalasin D. For all experiments, Mφ were infected with endospores and incubated in MEM at 37°C with 5% CO₂ for 60 min. After 60 min, the percentage of endospore germination was calculated as described in the text. Each experiment was performed in triplicate with at least two separate preparations of labeled endospores, and results are reported with an error of ±1 standard deviation of the mean.