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Giardia
 
 
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Giardia is a genus of anaerobic
Anaerobic

Anaerobic is a technical word which literally means without air , as opposed to aerobic .In wastewater treatment the absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of a common electron acceptor such as nitrate, sulfate or oxygen....
 flagellate
Flagellate

Flagellates are cell s with one or more whip-like organelles called flagellum. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla....
d protozoa
Protozoa

Protozoan are microorganisms classified as unicellular eukaryotes. While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate....
n parasites that colonise and reproduce in the small intestines of several vertebrates, causing giardiasis
Giardiasis

IntroductionGiardiasis in humans is caused by the infection of the small bowel by a single-celled organism called Giardia lamblia. Giardiasis occurs worldwide with a prevalence of 20-30% in developing countries....
. Their life cycle alternates between an actively swimming trophozoite
Trophozoite

A trophozoite is the activated, feeding stage in the life cycle of protozoan parasites such as the malaria-causing Plasmodium falciparum ....
 and an infective, resistant cyst
Microbial cyst

A microbial cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist, that helps the organism to tide over unfavorable environmental conditions....
. The genus was named after French zoologist Alfred Mathieu Giard
Alfred Mathieu Giard

Alfred Mathieu Giard was a French zoologist born in Valenciennes on August 8, 1846. He was a professor at the Sorbonne, at ?cole centrale de Lille and served as director of the marine laboratory in Wimereux ....
.

other diplomonad
Diplomonad

The diplomonads are a group of flagellates, most of which are parasitic. They include most notably Giardia lamblia, which causes giardiasis in humans....
s, Giardia have two nuclei
Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
, each with four associated flagella and lack both mitochondria
Mitochondrion

In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryote cell . These organelles range from 0.5–10 micrometers in diameter....
 and a Golgi apparatus
Golgi apparatus

The Golgi apparatus is an organelle found in most eukaryote Cell . It was identified in 1898 by the Italian physician Camillo Golgi and was named after him....
.






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Giardia is a genus of anaerobic
Anaerobic

Anaerobic is a technical word which literally means without air , as opposed to aerobic .In wastewater treatment the absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of a common electron acceptor such as nitrate, sulfate or oxygen....
 flagellate
Flagellate

Flagellates are cell s with one or more whip-like organelles called flagellum. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla....
d protozoa
Protozoa

Protozoan are microorganisms classified as unicellular eukaryotes. While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate....
n parasites that colonise and reproduce in the small intestines of several vertebrates, causing giardiasis
Giardiasis

IntroductionGiardiasis in humans is caused by the infection of the small bowel by a single-celled organism called Giardia lamblia. Giardiasis occurs worldwide with a prevalence of 20-30% in developing countries....
. Their life cycle alternates between an actively swimming trophozoite
Trophozoite

A trophozoite is the activated, feeding stage in the life cycle of protozoan parasites such as the malaria-causing Plasmodium falciparum ....
 and an infective, resistant cyst
Microbial cyst

A microbial cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist, that helps the organism to tide over unfavorable environmental conditions....
. The genus was named after French zoologist Alfred Mathieu Giard
Alfred Mathieu Giard

Alfred Mathieu Giard was a French zoologist born in Valenciennes on August 8, 1846. He was a professor at the Sorbonne, at ?cole centrale de Lille and served as director of the marine laboratory in Wimereux ....
.

Characteristics

Like other diplomonad
Diplomonad

The diplomonads are a group of flagellates, most of which are parasitic. They include most notably Giardia lamblia, which causes giardiasis in humans....
s, Giardia have two nuclei
Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
, each with four associated flagella and lack both mitochondria
Mitochondrion

In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryote cell . These organelles range from 0.5–10 micrometers in diameter....
 and a Golgi apparatus
Golgi apparatus

The Golgi apparatus is an organelle found in most eukaryote Cell . It was identified in 1898 by the Italian physician Camillo Golgi and was named after him....
. However they are now known to possess mitochondrial relics, called mitosome
Mitosome

A mitosome is an organelle found in some unicellular eukaryote organisms. The mitosome has only recently been found and named, and its function has not yet been well characterized....
s. These are not used in ATP
Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
 synthesis the way mitochondria are, but are involved in the maturation of iron-sulfur protein
Iron-sulfur protein

Iron-sulfur proteins are proteins characterized by the presence of iron-sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states....
s.. The synapomorphies
Synapomorphy

In evolutionary biology, a synapomorphy is a derived character state shared by two or more terminal groups and inherited from their most recent common ancestor....
 of genus Giardia include cells with duplicate organelles, absence of cytostome
Cytostome

A cytostome or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacuoles....
s, and ventral adhesive disc

Systematics

About 40 species have been described from different animals, but many of them are probably synonyms. Currently, five to six morphologically distinct species are recognised. Giardia lamblia
Giardia lamblia

File:Giardia life cycle en.svgGiardia lamblia is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis....
 (=G. intestinalis, =G. duodenalis) is a well-known human parasite, G. muris is found from other mammals, G. ardeae and G. psittaci from birds, G. agilis from amphibians and G. microti from voles. Other described, (but not certainly valid) species include:
  • Giardia beckeri
  • Giardia beltrani
  • Giardia botauri
  • Giardia bovis
  • Giardia bradypi
  • Giardia canis
  • Giardia caprae
  • Giardia cati
  • Giardia caviae
  • Giardia chinchillae
  • Giardia dasi
  • Giardia equii
  • Giardia floridae
  • Giardia hegneri
  • Giardia herodiadis
  • Giarida hyderabadensis
  • Giardia irarae
  • Giardia marginalis
  • Giardia melospizae
  • Giardia nycticori
  • Girdia ondatrae
  • Giardia otomyis
  • Giardia pitymysi
  • Giardia pseudoardeae
  • Giardia recurvirostrae
  • Giardia sanguinis
  • Giardia serpentis
  • Giardia simoni
  • Giardia sturnellae
  • Giardia suricatae
  • Giardia tucani
  • Giardia varani
  • Giardia viscaciae
  • Giardia wenyoni
. Genetic and biochemical studies have revealed the heterogenity of Giardia lamblia
Giardia lamblia

File:Giardia life cycle en.svgGiardia lamblia is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis....
, which contains probably at least eight lineages or cryptic species.

See also

  • List of parasites (human)
    List of parasites (human)

    EndoparasitesProtozoan organismsHelminths organisms Other organismsEctoparasites...