There are two main types of anaerobes:
* Obligate anaerobes: These organisms cannot survive in the presence of oxygen. Oxygen is actually toxic to them.
* Facultative anaerobes: These organisms can survive with or without oxygen. They can switch between aerobic respiration (using oxygen) and anaerobic respiration (not using oxygen) depending on the environment.
Some examples of anaerobes include bacteria that live in the gut, soil, and deep ocean vents.
