Coccus-shaped Bacillus subtilis cells are inhibited at stage 0 of sporulation

RodA and rodB mutations cause rod-shaped Bacillus subtilis cells to become coccus-shaped when the growth temperature is increased from 30 to 45°C. At 30°C four rod strains sporulated as well as the genetically closely related rod⁺ strains. In contrast, at 45°C the sporulation frequencies of rod strains decreased approximately 10²-to 10⁴-fold, while those of rod⁺ strains remained either unchanged or decreased only slightly. Temperature shift experiments and ultrastructural data indicated that coccus-shaped cells were unable to form prespore septa and were, therefore, inhibited at stage 0 of sporulation.