What does the term "facultative anaerobe" mean?

The term "facultative anaerobe" refers to organisms that have the ability to grow in both the presence and absence of oxygen. This means that facultative anaerobes can utilize aerobic respiration when oxygen is available, allowing for more efficient energy production. However, when oxygen is not available, they can switch to anaerobic processes such as fermentation to obtain energy. This versatility is key to their survival in varying environmental conditions.

In contrast, obligate aerobes require oxygen for growth and cannot thrive without it, while obligate anaerobes are harmed or killed by oxygen and can only grow in its absence. The ability to adapt to different oxygen levels gives facultative anaerobes a significant advantage in diverse ecosystems, as they can exploit a wider range of habitats.