FIG. 1.

Impact of pH and sorbic acid on amino acid- and inosine-induced germination of spores derived from B. cereus ATCC 14579 and its ΔgerR mutant. Heat-activated spores of B. cereus ATCC 14579 (squares) (A and B) and its ΔgerR mutant (circles) (A and C) were incubated at pH 5.5 (open symbols) or pH 5.5 plus 3 mM HSA (closed symbols). At time zero, the following germinants were used to induce germination: l-alanine (1 mM) (A), l-glutamine (1 mM) (B), and inosine (1 mM) (C). The vertical axis expresses the percentage of OD₆₀₀ at the indicated time points, relative to that determined at time zero. The drop in optical density signifies germination. After 2 h of incubation, the pH in sorbic acid-stressed spore cultures was raised to pH 7.1 by addition of 2 M NaOH (indicated with the black arrow). Graphs show the results from triplicate experiments.