Heterolobosea

Heterolobosea is a class of Amoebozoa, a major lineage of eukaryotes. Members are primarily free-living amoebae that can transition between amoeboid and other forms, most notably a transient flagellated cell. The best studied representatives belong to the genus Naegleria and related taxa.

Life cycle and morphology: Trophozoites are usually lobose and feed by phagocytosis. Many species can produce a short-lived, two-flagellated stage that allows rapid dispersal, and, in some species, a dormant cyst forms under environmental stress. The flagellated stage has two flagella and is typically nonfeeding and short-lived.

Ecology and distribution: Heteroloboseans are found in soil, freshwater, and sediment, including warm springs and man-made water systems. They are largely free-living and play roles in microbial food webs; some species tolerate chlorination and other disinfection measures.

Medical relevance: The best known human pathogen is Naegleria fowleri, which can cause primary amebic meningoencephalitis when nasal exposure occurs, usually in warm freshwater environments. Disease is rare but often fatal. Most heteroloboseans are nonpathogenic to humans.

Taxonomy and classification: Heterolobosea is a class within the Amoebozoa. Its precise placement has shifted with molecular data, and its boundaries relative to other Amoebozoan groups have been subject to revision. The group comprises several genera, including Naegleria and others, united by the ability to alternate between amoeboid and flagellated forms.