Fig. 1.

Effect of Tb³⁺ on DPA release during spore germination. DPA release during germination of intact (○, •) or chemically decoated (▿, ▾) spores in the presence (•, ▾) or absence (○, ▿) of TbCl₃ was measured as described in the text. In panels A, B, and C, the TbCl₃ concentration was either 50 μM (•) or 10 μM (▾), and in panel D TbCl₃ was at 50 μM (•, ▾). (A) B. subtilis PS533 (wild-type) spores germinating in 2 mM l-valine; (B) B. subtilis PS533 (wild-type) spores germinating in 40 mM dodecylamine; (C) B. cereus spores germinating in 40 mM NH₄Cl plus 10 mM l-alanine; and (D) B. megaterium spores germinating in 10 mM d-glucose. With intact spores germinating with nutrient germinants, the amounts of fluorescence in the TbCl₃ assay were similar with 10 μM and 50 μM TbCl₃ present throughout the assay (data not shown).