Final answer:
Pasteurization does not kill endospores because it does not reach high enough temperatures. Methods such as autoclaving, incineration, and hot-air sterilization can kill endospores due to the extreme temperatures they employ.
Step-by-step explanation:
A student has asked which of the following does not kill endospores:
- A) autoclaving
- B) incineration
- C) hot-air sterilization
- D) pasteurization
- E) All of the above kill endospores
The correct answer is D) pasteurization. Autoclaving, incineration, and hot-air sterilization are methods capable of killing endospores due to the high temperatures they reach, which are above the boiling point of water.
Endospores are highly heat-resistant and can survive boiling temperatures. However, pasteurization only kills heat-sensitive pathogens and reduces the number of spoilage-causing microbes, but does not achieve temperatures high enough to kill endospores.
Endospores are a defensive strategy against unfavorable conditions used by certain bacteria, such as those of the genera Bacillus and Clostridium. They are notoriously difficult to destroy due to their resilience.
Special methods like autoclaving (which involves pressurized steam-heating) are used to ensure complete sterilization, particularly in clinical settings where the presence of highly resistant microbes like endospores pose a significant risk.