FIG 2.

Silicate uptake and spore acid resistance of the B. cereus wild type and ΔcotB1B2 and ΔcotG mutants. (A) Silicate concentrations in the culture supernatant of the wild-type (●), ΔcotB1B2 (○), and ΔcotG (▲) strains were measured at the indicated times after inoculation into mR2A medium supplemented with 100 μg ml⁻¹ silicate. Microscopic observation showed that engulfed forespores formed during the 12 to 24 h period and that mature spores were gradually released from the mother cells after 36 h. (B) Viability of wild-type (circles) and ΔcotB1B2 (triangles) spores in 0.2 N HCl. Spores were produced in the presence (closed symbols) or absence (open symbols) of silicate. The data represent the means and standard deviations of the results of at least three independent experiments.