Texas A&M University (TAMU) BIOL206 Introductory Microbiology Lab Practice Exam 1

Bacterial endospores represent the most resistant form of bacteria due to their unique structural and metabolic features that allow them to survive extreme environmental conditions. When environmental stressors such as heat, desiccation, radiation, or nutrient depletion are present, certain bacterial species, particularly from the genera Bacillus and Clostridium, can enter a state of dormancy by forming endospores. These spores are highly resilient, being able to withstand extreme temperatures, high pressure, desiccation, and even the effects of disinfectants and radiation that would typically destroy vegetative bacterial cells.

The structure of endospores contributes to their resistance. They have a tough outer coating that protects them from environmental hazards, as well as a low water content and a lack of metabolic activity, making them less susceptible to detrimental changes in their surroundings. Because of these features, endospores require extreme treatments, such as autoclaving (a process that uses high-pressure steam) or chemical treatments that are much harsher than those used to eliminate vegetative cells.

In contrast, bacterial vegetative cells are actively metabolizing and are therefore considerably more sensitive to normal cleaning agents and heat. Fungal spores, while resistant to some extent, do not have the same