Anaerobes are organisms that can live without oxygen, with some needing an oxygen-free environment to survive. They can cause disease or be beneficial, and are isolated from aerobic organisms using liquid culture. Fish access oxygen differently than surface-dwelling organisms. Anaerobes can be used to produce chemicals and other useful products.
An anaerobe is an organism that can thrive in an oxygen-free environment and, in some cases, may actually need an environment with limited or no oxygen to live. Most anaerobes are microorganisms, but some larger organisms are also anaerobes, such as the massive tubeworms found near hydrothermal vents. Anaerobes affect humans for a variety of reasons, not the least of which is that some can cause infection and disease if ingested by humans.
A true anaerobe is known as “obligate,” because it needs an oxygen-free environment and cannot survive in areas with atmospheric oxygen. Facultative anaerobes, on the other hand, can live in areas with varying levels of oxygen, taking advantage of changing conditions. Other types of anaerobes have different than normal oxygen requirements, such as microaerophilic organisms, which need low levels of oxygen to live.
Some of these organisms use fermentation to gather energy, while others may use anaerobic respiration, where gas exchange occurs with gases other than oxygen. In the case of facultative anaerobes, depending on the environment in which the organism lives, both anaerobic and conventional respiration can take place.
Scientists can isolate aerobic organisms from anaerobic organisms with the use of a liquid culture. Aerobic organisms will accumulate near the surface of the culture so they have access to oxygen, while obligate anaerobes will settle at the bottom. Facultative, microaerophilic and related organisms will spread out in the culture medium to find the oxygen saturation levels they need.
Being able to live in water does not necessarily make an organism an anaerobic, although water is a liquid. In fact, water is quite rich in dissolved oxygen, and as a result, most organisms that live in water require oxygen to live, although they access oxygen differently than surface-dwelling organisms. Fish, for example, carry out gas exchange with their gills, pumping water through their gills and capturing dissolved oxygen as it passes.
In some cases, an anaerobe can cause disease in humans. Botulinum toxin, for example, is created by anaerobic bacteria that can live in canned food that has been contaminated. Other anaerobes may actually be beneficial, as is the case with organisms that ferment milk to create yogurt, cheese and other dairy products. Fermentation is also key to making wine and beer. An anaerobe can also be used in the production of a large assortment of chemicals and other useful products, with the use of a bioreactor in which a controlled and organism-friendly environment can be maintained.
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