Definition of aerotolerant anaerobes
Aerotolerant anaerobes are bacteria that do not require oxygen for their growth but can tolerate the presence of air or oxygen. Since aerotolerant bacteria do not require oxygen, they are classified as anaerobic organisms. However, obligate anaerobes can be damaged by reactive oxygen molecules.
The aerotolerant bacteria can survive in the presence of oxygen but cannot use it for growth and metabolic activity. The aerotolerant anaerobes use fermentation to produce energy in the form of ATP.
Some of the references consider the aerotolerant anaerobes to be facultative anaerobes since both can still survive in the presence of oxygen, unlike obligate anaerobes. The only difference is that facultative anaerobes may have the ability to utilize oxygen if it is available; Aerotolerant anaerobes do not utilize oxygen.
How Aerotolerant Anaerobes Survive Aerobic Environment?
Aerotolerant bacteria can survive even when exposed to oxygenated air because they employ strategies to protect themselves. One of these is to produce enzymes that counteract the destructive effects of some deadly forms of oxygen.
For example, superoxide dismutase is an enzyme that can convert the superoxide anion to ground-state oxygen and hydrogen peroxide. Hydrogen peroxide, in turn, is broken down by another enzyme, e.g. catalase or peroxidase degraded.
How Aerotolerant Anaerobes Produce Energy
Adenosine triphosphate is a form of energy that the human body creates using oxygen. ATP is required to complete all tasks. ATP is formed from food through the process of aerobic cellular respiration. In aerobic cellular respiration, the body converts food energy into ATP.
“If oxygen is required for the production of ATP, how can aerotolerant anaerobic bacteria survive without oxygen?” Aerotolerant bacteria use fermentation instead of aerobic cellular respiration.
Although fermentation produces less ATP than aerobic respiration, fermentation was sufficient to provide them with sufficient cellular energy.” (Study.com, 2021)
Where are Aerotolerant organisms found?
Many ecosystems still lack molecular oxygen. Some are found in difficult conditions, such as in the earth’s crust or in the depths of the oceans, while others are common, such as in drains, marshes, and swamps.
In the body of humans and animals, there are certain regions with little or almost no oxygen that create an anaerobic habitat for microbes.
Aerotolerant Anaerobe Examples
What organisms are aerotolerant? Some examples of aerotolerant anaerobes are as follows:
- Streptococci and Lactobacillus spp. found in oral microbiota are the main aerotolerant anaerobic bacteria.
- An example of a microaerophile is Campylobacter jejuni which shows growth in less amount of oxygen. It causes gastrointestinal infections.
- Cutibacterium acnes is also an example of an aerotolerant anaerobe.
