<prompt> Which of the following is used as an indicator for plasma sterilization?Bacillus subtilisBacillus stearothermophilusBacillus pumilusClostridium tetani  <response>: 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 55-60oC and its spores require an exposure of 12 minutes at 121oC to be killed. Ref: Textbook of Microbiology by Ananthanarayan, 8th edition, Page 32; 6th edition, Page 27. 