FIG. 1.

Spore germination and outgrowth. (A) After the addition of Bacillus subtilis spores to prewarmed germination medium (see Materials and Methods), germination and outgrowth were monitored by measuring changes in the optical density at 600 nm (OD₆₀₀) (○). In addition, the release of dipicolinic acid (DPA) (▴) was monitored as a measure for the efficiency of spore germination. (B) Extracellular glucose, pyruvate, and acetate levels were monitored during germination and outgrowth. The switch from an endogenous metabolism to the use of extracellular metabolites was indicated by the decrease of the glucose concentration and increase of the acetate concentration in the medium. Pyruvate levels were found to decrease rapidly late in outgrowth. (C) Morphological changes during spore germination and outgrowth were investigated by microscopic analysis. Cells harvested at various time points during germination and outgrowth were fixed and monitored by phase-contrast microscopy (top row) and fluorescence microscopy following DNA DAPI (4′,6′-diamidino-2-phenylindole) straining (bottom row).