Final answer:
Bacterial cells are typically killed at temperatures above 60°C and below 20°C. However, endospores can withstand extreme temperatures and survive within the temperature range that kills vegetative bacterial cells.
Step-by-step explanation:
Bacterial cells are usually killed within a specific temperature range. While the exact range can vary depending on the bacterial species, most bacterial cells are typically killed at temperatures above 60°C (140°F) and below 20°C (68°F). Heat denatures proteins and disrupts cellular processes, leading to the death of bacterial cells. However, it's important to note that some bacteria have the ability to form endospores, which are dormant and highly resistant structures. Endospores can withstand extreme temperatures and harsh conditions, allowing them to survive even within the temperature range that kills vegetative bacterial cells.