Everything about Entamoeba totally explained
Entamoeba is a
genus of
Amoebozoa found as internal
parasites or
commensals
of animals. Several species are found in humans.
Entamoeba histolytica is the pathogen responsible for
amoebiasis (which includes amoebic
dysentery and amoebic liver abscesses), while others such as
Entamoeba coli and
E. dispar are harmless. With the exception of
Entamoeba gingivalis, which lives in the mouth, and
E. moshkovskii, which is frequently isolated from river and lake sediments, all
Entamoeba species are found in the
intestines of the animals they infect.
Entamoeba cells are small, with a single
nucleus and typically a single lobose pseudopod taking the form of a clear anterior bulge. They have a simple life cycle. The trophozoite (feeding-dividing form) is approximately 10-20 μm in diameter and feeds primarily on bacteria. It divides by simple binary fission to form two smaller daughter cells. Almost all species form cysts, the stage involved in transmission (the exception is
E. gingivalis). Depending on the species, these can have one, four or eight nuclei and are variable in size; these characteristics help in species identification.
Entamoeba belongs to the
Archamoebae, which are unusual in lacking
mitochondria. This group also includes
Endolimax, which also lives in animals and is similar in appearance to
Entamoeba, although this may partly be due to convergence. Certain other genera of symbiotic amoebae, such as
Endamoeba, might prove to be synonyms of
Entamoeba but this is still unclear.
Studying
Entamoeba invadens,
David Biron of the
Weizmann Institute of Science and coworkers found that about one third of the cells are unable to separate unaided and recruit a neighboring amoeba (dubbed the "midwife") to complete the fission. He writes:
» When an amoeba divides, the two daughter cells stay attached by a tubular tether which remains intact unless mechanically severed. If called upon, the neighbouring amoeba midwife travels up to 200 μm towards the dividing amoeba, usually advancing in a straight trajectory with an average velocity of about 0.5 μm/s. The midwife then proceeds to rupture the connection, after which all three amoebae move on.
They also reported a similar behavior in
Dictyostelium.
Further Information
Get more info on 'Entamoeba'.
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