Fig. 2.
Microscopic analysis of sporulation. Phase-contrast light microscopy (A.) and negative stained TEM (B.) of the wild type parental strain (R20291), spoVDCd mutant (R20291ΔspoVD) and complemented strain (R20291ΔspoVD pyrE:spoVD). A. Cultures were imaged at day 5 of the sporulation assays shown in Fig. 1. Spores are visible as ovoid phase bright objects i, while vegetative cells are phase dark bacilli. B. TEM imaging of developing spores clearly shows normal spore development in R20291 and R20291ΔspoVD pyrE:spoVD; the densely stained core surrounded by a thick, largely unstained cortex layer. Cultures of R20291ΔspoVD contained no morphologically normal developing spores, although fully engulfed prespores without a cortex (example shown) were common.