FIG 3.

TEM micrographs of B. subtilis spores incubated with or without Tb³⁺. Spores incubated without (A and C) or with (B and D) Tb³⁺ were examined by TEM. Panels C and D show higher magnifications than panels A and B (87). TEM, transmission electron microscopy; Ct, spore coat; Sm, spore matrix. The composition of Sm has not yet been well defined, but it is hypothesized to contain both proteins and carbohydrates (87). White arrows indicate the spore coat, and black arrows denote electron-dense areas where Tb³⁺ is adsorbed. (All images are reprinted from reference 87 with permission.)