Fig. 3.

Emergence of vegetative cells. (a–g) Series of AFM height images showing 60- to 70-nm-deep apertures in the rodlet layer (indicated with arrows in b) that gradually enlarged (c and d), and subsequently eroded the entire spore coat (e). Germ cells emerged from these apertures. (e) Before germ emergence from the spore coat, the peptidoglycan cell wall structure was evident. (f and g) At an early stage of emergence, the cell wall was still partly covered by spore remnants (f), whereas immediately before cell emergence, the cell wall was free of spore integument debris (g). The germ cell surface contained 1– to 6-nm fibers forming a fibrous network enclosing pores of 5–100 nm. Images in a–g were collected on the same spore as those shown in Fig. 1 e and f. Elapsed germination time (in hr:min) was as follows: (a) 3:40, (b) 5:45, (c) 7:05, (d) 7:30, (e) 7:45, (f) 7:15, (g) 7:50. (h) In separate experiments, cultured vegetative B. atrophaeus cells were adhered to gelatin surfaces and imaged in water. AFM height images show a slightly denser, similar fibrous network compared with the germ cell network structure (g), with 5– to 50-nm pores. (Inset) The imaged part (h) of the entire cell is indicated with a white rectangle. [Scale bars: 500 nm (a-e), 100 nm (f–h), and 1 μm (h Inset).]