Influence of the sporulation temperature on the impact of the nutrients inosine and l-alanine on Bacillus cereus spore germination

The effect of sporulation temperature on Bacillus cereus spore germination triggered by the nutrient germinants inosine and l-alanine was investigated. The germination (expressed as % A600 nm fall) of heat-activated spores of B. cereus strain ATCC14579 produced at 20 and 37 °C, and of psychrotrophic strains LM9 and D15 produced at 15 and 37 °C was followed in a germination buffer containing inosine at concentrations between 0.01 and 10 mmol l−1, or l-alanine between 1 and 100 mmol l−1. Spores wet-heat resistance at 90 °C was also determined. Spores of the three strains produced at the lowest temperatures generally showed a higher germination capacity in response to both inosine and in l-alanine than those produced at 37 °C, and were also more susceptible to heat. Low sporulation temperature is confirmed as a detrimental factor to B. cereus spore wet-heat resistance, and conversely gave spores with a sensitivity to the nutrient germinants inosine and l-alanine higher than that of spores formed close to the maximal sporulation temperature.