Final answer:
The biological indicator used for EtO, gas plasma, and dry heat sterilization contains spores of Bacillus subtilis, which are used due to their high resistance to sterilization processes.
Step-by-step explanation:
The biological indicator used for ethylene oxide (EtO), gas plasma, and dry heat sterilization contains spores of Bacillus subtilis. These bacterial spores are employed because of their resilience to sterilization processes. Internal indicators using spores from bacteria such as Bacillus subtilis, Geobacillus stearothermophilus, Bacillus atrophaeus, or Bacillus pumilus are used to confirm that a sterilization protocol has been effective. Bacillus subtilis is chosen for its resistance to harsh environments, which makes the spores ideal for testing sterilization methods like EtO, dry heat, and gas plasma.