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Naegleria
Naegleria /nɛˈɡlɪəriə/ is a genus consisting of 47 described species of protozoa often found in warm aquatic environments as well as soil habitats worldwide. It has three life cycle forms: the amoeboid stage, the cyst stage, and the flagellated stage, and has been routinely studied for its ease in change from amoeboid to flagellated stages. The Naegleria genera became famous when Naegleria fowleri, the causative agent of the usually fatal human and animal disease primary amoebic meningoencephalitis (PAM), was discovered in 1965. Most species in the genus, however, are incapable of causing disease.
The genus Naegleria is named after the German protozoologist, Kurt Nägler.
In 1899, Franz Schardinger discovered an amoeba that had the ability to transform into a flagellated stage. He named the organism Amoeba gruberi, which was later changed to the genus Naegleria in 1912 by Alexeieff. Before 1970, the genus was generally used as a model organism to study the changes from amoeboid to flagellated stages. However it garnered much more attention when a human pathogenic species (Naegleria fowleri) was discovered in Australia in 1965, and described in 1970.
Naegleria is found worldwide in typically aerobic warm aquatic environments (freshwater such as lakes and rivers) and soil habitats. As a typically free living genus, it feeds on bacteria and can be maintained on a diet of gram negative bacteria. It feeds via phagocytosis. The few species that are pathogenic seem to be characteristically thermophilic, preferring warmer temperatures such as nuclear power plant cooling water. One species, Naegleria fowleri, can be an opportunistic and usually fatal pathogen of humans if it enters the depths of the nasal cavity.
Naegleria are free-living amoebae, with some strains being opportunistic pathogens. Cells range from 10-25 um depending on the life stage it is currently in. Species are not classified morphologically anymore but historically have been by flagellar shape. New species are often defined by ribosomal DNA sequences. The unicellular organism's cytoplasm has distinct separations of an ectoplasm (outer) and endoplasm (inner). As a mitochondriate, aerobic organism it has many mitochondria in the endoplasm. The endoplasm also contains ribosomes, food vacuoles, contractile filaments/vacuoles, and protoplasmic filaments. Notably, Golgi is not visibly identifiable although expression of Golgi-associated machinery has been identified. It has a nucleus with a prominent nucleolus.
Naegleria has 3 different life cycle stages: amoebae, cyst, and flagellate.
The amoebae stage is the feeding stage and has blunt pseudopodia (lobopodia) that give the cell an overall irregular, yet generally cylindrical shape. The overall size is usually around 10–20 um at this stage. The pseudopodia are actin based extensions of the body and form at irregular regions of the cell. Movement occurs in this stage via extending the pseudopodia, and having the cytoplasmic internal contents follow subsequently. As the feeding stage of the organism, pseudopodia are also used to engulf prey, such as bacteria. This is also the stage that the organism spends the most time in, and also the reproductive phase. Reproduction occurs here by binary fission and it can reproduce every 1.6 hours on a bacterial diet. Reproductive division involves promitosis, or intranuclear mitosis, which does not occur with nuclear envelope breakdown. Sexual reproduction has not been observed in this genus but the genes for meiosis do exist in the genome.
The cyst stage is a double walled spherical stage. The double wall consists of a thick endocyst and a thin endocyst. The cyst contains usually 2-8 pores (often depending on the species) and is formed when conditions become adverse, such as residing in non optimal temperature. Cysts are favourable as they are naturally resistant to environmental hardships. When adverse conditions are restored to normal, the organism can escape the cyst through the pores in its amoeboid form. Cysts have been observed to be formed in all but one species where the ability to form a cyst is inhibited by a bacterial parasite.
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Naegleria
Naegleria /nɛˈɡlɪəriə/ is a genus consisting of 47 described species of protozoa often found in warm aquatic environments as well as soil habitats worldwide. It has three life cycle forms: the amoeboid stage, the cyst stage, and the flagellated stage, and has been routinely studied for its ease in change from amoeboid to flagellated stages. The Naegleria genera became famous when Naegleria fowleri, the causative agent of the usually fatal human and animal disease primary amoebic meningoencephalitis (PAM), was discovered in 1965. Most species in the genus, however, are incapable of causing disease.
The genus Naegleria is named after the German protozoologist, Kurt Nägler.
In 1899, Franz Schardinger discovered an amoeba that had the ability to transform into a flagellated stage. He named the organism Amoeba gruberi, which was later changed to the genus Naegleria in 1912 by Alexeieff. Before 1970, the genus was generally used as a model organism to study the changes from amoeboid to flagellated stages. However it garnered much more attention when a human pathogenic species (Naegleria fowleri) was discovered in Australia in 1965, and described in 1970.
Naegleria is found worldwide in typically aerobic warm aquatic environments (freshwater such as lakes and rivers) and soil habitats. As a typically free living genus, it feeds on bacteria and can be maintained on a diet of gram negative bacteria. It feeds via phagocytosis. The few species that are pathogenic seem to be characteristically thermophilic, preferring warmer temperatures such as nuclear power plant cooling water. One species, Naegleria fowleri, can be an opportunistic and usually fatal pathogen of humans if it enters the depths of the nasal cavity.
Naegleria are free-living amoebae, with some strains being opportunistic pathogens. Cells range from 10-25 um depending on the life stage it is currently in. Species are not classified morphologically anymore but historically have been by flagellar shape. New species are often defined by ribosomal DNA sequences. The unicellular organism's cytoplasm has distinct separations of an ectoplasm (outer) and endoplasm (inner). As a mitochondriate, aerobic organism it has many mitochondria in the endoplasm. The endoplasm also contains ribosomes, food vacuoles, contractile filaments/vacuoles, and protoplasmic filaments. Notably, Golgi is not visibly identifiable although expression of Golgi-associated machinery has been identified. It has a nucleus with a prominent nucleolus.
Naegleria has 3 different life cycle stages: amoebae, cyst, and flagellate.
The amoebae stage is the feeding stage and has blunt pseudopodia (lobopodia) that give the cell an overall irregular, yet generally cylindrical shape. The overall size is usually around 10–20 um at this stage. The pseudopodia are actin based extensions of the body and form at irregular regions of the cell. Movement occurs in this stage via extending the pseudopodia, and having the cytoplasmic internal contents follow subsequently. As the feeding stage of the organism, pseudopodia are also used to engulf prey, such as bacteria. This is also the stage that the organism spends the most time in, and also the reproductive phase. Reproduction occurs here by binary fission and it can reproduce every 1.6 hours on a bacterial diet. Reproductive division involves promitosis, or intranuclear mitosis, which does not occur with nuclear envelope breakdown. Sexual reproduction has not been observed in this genus but the genes for meiosis do exist in the genome.
The cyst stage is a double walled spherical stage. The double wall consists of a thick endocyst and a thin endocyst. The cyst contains usually 2-8 pores (often depending on the species) and is formed when conditions become adverse, such as residing in non optimal temperature. Cysts are favourable as they are naturally resistant to environmental hardships. When adverse conditions are restored to normal, the organism can escape the cyst through the pores in its amoeboid form. Cysts have been observed to be formed in all but one species where the ability to form a cyst is inhibited by a bacterial parasite.