Breath of Life: Bacteria's Guide to Survival

By Lauryn Davis

Oxygen, the life-giving gas that supports most life forms on Earth, presents a contradiction for many microorganisms. Considering oxygen is not always readily available, this creates a challenge. Bacteria are masters at adaptation and have evolved diverse strategies to survive in environments presented with varying oxygen concentrations.

There are some bacteria that can only survive in oxygen-rich environments and rely as oxygen as a terminal electron acceptor in their respiratory chain. These bacteria are known as aerobic bacteria. Through aerobic respiration, these bacteria efficiently convert organic molecules into energy, producing ATP to fuel cellular processes.

On the other hand, there is bacteria where oxygen is toxic and they can only survive in environments where oxygen is scarce or absent relying on alternative electron acceptors or fermentation to generate energy. These bacteria are known as anaerobic bacteria. Through anaerobic respiration, some anaerobic bacteria utilize alternative electron acceptors such as nitrite, sulfate, or carbon dioxide in place of oxygen leading to the production of ATP. When there is an absence of external electron acceptors, some anaerobic bacteria resort to fermentation. This generally involves the partial oxidation of glucose to produce ATP and makes end products of lactate, ethanol, or acetate.

Bacteria is divided into aerobic and anaerobic conditions and within that are subcategories including; obligate aerobes, facultative anaerobes, obligate anaerobes, aerotolerant anaerobes, and microaerophiles (see diagram).