Geobacillus

Geobacillus is a genus of Gram positive, aerobic, thermophilic bacteria, to which several species of Bacillus have been transferred, including B. stearothermophilus and B. thermoleovorans. They are notorious in the food industry for spoiling canned and heat-processed products: Geobacillus stearothermophilus spores survive inadequate retorting and cause flat-sour spoilage of canned vegetables, growing at temperatures that defeat most competitors. Its extreme heat resistance makes it the standard biological indicator for validating steam sterilisation processes, with spore strips or suspensions used to prove that autoclaves and retorts deliver the required lethality.