Life Cycle
Naegleria fowleri occurs in three forms: a cyst, a trophozoite (ameboid) and a flagellate.
- Cyst stage
Trophozoites encyst due to unfavorable conditions. Factors that induce cyst formation can include food deprivation, crowding, desiccation, accumulation of waste products, and cold temperatures. N. fowleri has been found to encyst at temperatures below 10°C.
- Trophozoite stage
This reproductive stage of the protozoan organism, which transforms near 25°C and grows fastest at around 42°C, proliferates by binary fission. The trophozoites are characterized by a nucleus and a surrounding halo. They travel by pseudopodia, temporary round processes which fill with granular cytoplasm. The pseudopodia form at different points along the cell, thus allowing the trophozoite to change directions. In their free-living state, trophozoites feed on bacteria. In tissues, they phagocytize red blood cells and white blood cells and destroy tissue.
- Flagellate stage
This biflagellate form occurs when trophozites are exposed to a change in ionic concentration, such as placement in distilled water. The transformation of trophozoites to flagellate form occurs within a few minutes.
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