Giardia lamblia
A Microbial Biorealm page on the genus Giardia lamblia
Classification
Higher order taxa
| Domain | Eukaryota |
|---|---|
| (Unspecified rank) | Diplomonadida group |
| (Unspecified rank) | Diplomonadida |
| Family | Hexamitidae |
| Sub-family | Giardiinae |
| Genus | Giardia |
Species
Species: Giardia lamblia
Other names: Giardia intestinalis, Giardia duodenalis
|
NCBI: [1] |
Description and significance
Giardia lamblia is a flagellated, microaerophilic microorganism, first discovered by Van Leeuwenhoek in 1681, who found it in his own diarrheal stool. The G. lamblia trophozite, vegetative, motile form of G. lamblia is pear-shaped and have unique morphology such as two identical nuclei, a ventral disc for adhesion to the host intestine, and flagella [see also Structure]. The cyst is the reproductive form, and consists of a protective cyst wall as well as four nuclei.
The genus Giardia has been isolated from more than 40 species. The species G. lamblia is known to infect human, mammals, reptiles, and birds, cows, sheeps and pigs, depending on the strain (Adam 2001).
G. lamblia is one of the major cause of waterborne diseases worldwide (CDC, 2004), and infection results in giardiasis (characterized by malabsorption and severe diarrhea). Giardia-induced intestinal infection is particularly severe in developing world, where giardiasis occurrence relates heavily to water source contamination. In the united states, G. lamblia has been found in both drinking and recreational water. Due to the high prevalence of giardiasis, G. lamblia is of significant interest in the clinical research community. However the pathogenic mechanisms are not completely understood. [See also Pathology].
G. lamblia is also significant in evolutionary biology. Due to its lack of mitochondria, G. lamblia is believed to be diverged from one of the earliest lineages of eukaryotes before the endosymbiotic relationship of mitochondria began (the kingdom name “Archezoa” has been proposed). However, this theory is currently under debate. Emerging proofs in genetics, for example, by comparison of the gene encoding valyl-tRNA synthetase (Hashimoto et al, 1998) and discovery of complex cellular machineries, (such as localized, mitochondria-like electron-transport machinery, (Lloyd, 2002)) suggest they may be more advanced organisms, who were once mitochondria-bearing but lost them ever since. Sequencing of the complete genome of G. lambdia is current in progress, but results so far have already provided much insight into its evolutionary history.
Genome structure
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
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Ecology
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Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
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References
Edited by student of Rachel Larsen
