Bacillus stearothermophilus

Geobacillus stearothermophilus (until 2001 classified as Bacillus stearothermophilus ) is a spore-forming, gram- positive rod-shaped bacterium.

The cells have an average of 0.6 to 1 micron in diameter and a length between 2 and 3.5 microns. The optimum growth temperature is between 50 and 65 ° C, so that one of the Geobacillus stearothermophilus thermophilic organisms. At temperatures below 30 ° C, the cells no longer grow.

The formation of endospores occurs terminally, while the bacterial cell is distended clavate. The resistant spores are in the soil, in hot springs in the desert sand, in Arctic waters, the seabed, in food and found in compost, but only germinate under favorable conditions from. The bacterium is not pathogenic for humans and animals, so do not cause disease.

Geobacillus stearothermophilus is used as test germ for the success of thermal sterilization processes (eg autoclaving). For this purpose, for example, glass vials are used which contain a liquid nutrient medium, spores of Geobacillus stearothermophilus, and a color indicator. The vials are autoclaved and then incubated as usual, along with a non- autoclaved control ampule at approximately 60 ° C for several days. Metabolic activity of the cells is indicated by a color change of the indicator. Successful sterilized ampoules do not change their coloration therefore. Another application form are spore strips, it is filter paper strips on which the endospores were applied. To control the steam sterilization adding the spore strips in the autoclave, then they are placed in a nutrient solution and incubated as above. If sterilization is successful, there is no growth.

Geobacillus stearothermophilus is used to produce the enzyme BstBI.