The effect of metal ions commonly present in food on gene expression of sporulating Bacillus subtilis cells in relation to spore wet heat resistance.

Bacillus subtilis is a food spoilage spore-forming bacterium. The spores can be very heat-resistant and may cause problems in the production of foods. Varying the metal concentration in the sporulation media is known to influence the heat resistance of the spores. The effect of changing the metal composition of the sporulation media was monitored by means of transcriptome analysis. Heat resistance was measured based on the method described by Kooiman and the transcriptome analysis was performed with micro-arrays of B. subtilis wt168 DNA. The micro-array analysis showed that genes coding for the two small acid soluble proteins (SASPs a and b) were induced earlier during sporulation in the media that contained higher metal concentrations and produced thermal-resistant spores. The results also showed that the spores of a product isolate (strain B. subtilis A163) were much more heat-resistant than the spores produced under the same environmental conditions by strain B. subtilis PS832. In addition to other genes, SASP a was also significantly induced in cells of strain B. subtilis A163 at early to middle stages of sporulation