Endosymbiosis
Endosymbiosis is a condition in which an organism lives within the body or the cells of another organism. Thousands of organisms live in endosymbiosis. Examples of endosymbionic organisms include 1) the bacteria that live and reproduce within the digestive system of human beings and 2) nitrogen fixing bacteria that live on potato roots.
In many cases, endosymbiosis is obligate, where neither organism can survive without the other. However, this is not always true. In some cases, the host organism does not benefit from its endosymbiont, and in other cases the endosymbiont is downright harmful. Occasionally, the host can even be harmful to the endosymbiont.
Most known examples of endosymbiosis are of the mutually-beneficial type. Mitochondria and chloroplasts are generally thought to be endosymbionts within the eukaryotic cell. Some scientists also think that cilia, flagella, centrioles, and microtubules came about from a symbiosis between an early eukaryotic cell and a spirilla-type bacterium. Mitochondria, chloroplasts, and centrioles all contain a small amount of DNA (signifying that they may once have existed independently of their host), and independent organisms similar to each of these proposed endosymbionts are alive today.
In certain cases, endosymbionts are critical to studies of disease – for instance, malaria is an endosymbiont within mosquitoes. If we figure out how to eradicate the endosymbionic relationship, we may be able to eliminate the disease as well.
Web Resources On Endosymbiosis
Endosymbiosis and The Origin of Eukaryotes
Endosymbiosis in Evolution
Book Resources On EndosymbiosisEndosymbiosis of Animals With Plant Microorganisms by P. Buchner
Endocytobiology, Endosymbiosis and Cell Biology by Schwemmier & Schenk
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