Spores of which of the following are used as a control in an autoclave

Spores of Bacillus stearothermophilus are used as a control in an autoclave. “Sterilization control of autoclave: For determining the efficacy of moist heat sterilization, spores of Bacillus stearothermophilus are used as the test organism. This is a thermophilic organism with an optimum growth temperature of 55-60 degree and its spores require an exposure of 12 minutes at 121 degrees to be killed." “Plasma sterilization is a safe method to sterilize instruments at low temperature under vacuum. Vacuum is required to prevent large concentrations of species from absorbing the UV rays created by the plasma during the sterilization process. The bacterial organism most resistant to the sterilization technique was Bacillus stearothermophilus. The organism was then used in Survival Analysis Curve testing and was effectively sterilized to a level of <106 with 30 min of diffusion time using both survivor curve and fraction negative analysis. So that Bacillus stearothermophilus is used as a control in plasma sterilization.” “B. subtilis is used in Guthrie's test.” "Sterilization control of Hot air oven: The spores of a non-toxigenic strain of Clostridium tetani are used as a microbiological test of dry heat efficiency."