Which type of organism can switch between aerobic and anaerobic respiration?

Facultative anaerobes are organisms that can switch between aerobic and anaerobic respiration depending on the availability of oxygen. In the presence of oxygen, they utilize aerobic respiration, which is more efficient in terms of ATP production. However, when oxygen is scarce or absent, they can shift to anaerobic respiration or fermentation, allowing them to generate energy without relying on oxygen. This flexibility enables facultative anaerobes to thrive in various environments, such as soil or within the gastrointestinal tracts of animals.

In contrast, obligate aerobes strictly require oxygen for their metabolic processes and cannot survive without it. Strict anaerobes and obligate anaerobes cannot tolerate oxygen at all; they rely solely on anaerobic respiration and may even find oxygen toxic. Thus, facultative anaerobes are unique in their ability to adapt their respiration method based on environmental conditions, making them well-suited for varying habitats.