Which genera of bacteria are known for their ability to form spores?

Bacillus and Clostridium are well-known genera of bacteria that possess the ability to form spores, which enables them to survive in harsh environmental conditions. This spore formation is a vital survival mechanism, allowing these bacteria to enter a dormant state, rendering them resistant to extreme heat, desiccation, radiation, and chemical disinfectants.

Bacillus species are primarily aerobic or facultatively anaerobic and are commonly found in soil and decomposing organic matter. An example of a spore-forming Bacillus is Bacillus anthracis, the causative agent of anthrax.

Clostridium species are obligate anaerobes and can be found in environments where oxygen is limited, such as deep soil, decaying vegetation, and the intestines of animals. Clostridium botulinum, the bacterium responsible for botulism, exemplifies a spore-forming member of this genus.

By recognizing that both Bacillus and Clostridium have this ability to form spores, it is clear why the answer includes both genera, distinguishing them from others like Corynebacterium, which does not form spores and does not share that characteristic.