Plasmodium
Encyclopedia : P : PL : PLA : Plasmodium
- A plasmodium is also the macroscopic form of the unusual protozoa known as slime moulds.
Plasmodium is a genus of parasitic
protozoa, four species of which cause
malaria in humans. Other species infect other animals, including
birds,
reptiles and
rodents. In
1898 Ronald Ross demonstrated the existence of
Plasmodium in the stomach of the
Anopheles mosquito. For this discovery he won the
Nobel Prize in
1902. However some credit must also be given to the Italian professor,
Giovanni Battista Grassi, who showed that human malaria could only be transmitted by
Anopheles mosquitoes.
The four species of Plasmodium that attack humans are
The life cycle of
Plasmodium is very complex.
Sporozoites are injected by a biting female mosquito, and migrate to the
liver, where the
parasite invades hepatocytes. The parasite replicates into thousands of
merozoites, which then invade
red blood cells. Here the parasite grows from a ring-shaped form to a larger
trophozoite form. In the stage, the parasite divides several times to produce new merozoites, which leave the red blood cells and travel within the bloodstream to invade new red blood cells. Most merozoites continue this replicative cycle, but some merozoites differentiate into male or female sexual forms (
gametocytes) (also in the blood), which are taken up by the female
Anopheles mosquito. In the mosquito's midgut, the
gametocytes develop into
gametes and
fertilize each other, forming motile
zygotes called ookinetes. The ookinetes penetrate and escape the midgut, then embed themselves onto the exterior of the gut membrane. Here they divide many times to produce large numbers of tiny elongated
sporozoites. These sporozoites migrate to the salivary glands of the mosquito where they are injected into the blood of the next host the mosquito bites. The sporozoites move to the liver where they repeat the cycle.
On a molecular level, the parasite damages red blood cells using plasmepsin enzymes. Plasmepsins are aspartic acid proteases which degrade hemoglobin.
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.
