Percolozoa

Percolozoa is a clade of single-celled eukaryotes within the supergroup Excavata. Members are characterized by life cycles that can alternate between amoeboid and flagellated forms; many are facultatively dimorphic, forming lobose amoebae that migrate by pseudopods and flagellated cells that swim with two or more flagella. Some species also form dormant cysts under adverse conditions. Reproduction is primarily asexual by binary fission; sexual processes are poorly documented in this group.

Percolozoa are mostly free-living, found in soil and freshwater environments worldwide. They feed on bacteria and other microorganisms. They can tolerate a range of temperatures and are often isolated from warm or transient aquatic habitats.

The best-known genus is Naegleria, including Naegleria fowleri, the so-called brain-eating amoeba that can cause primary amoebic meningoencephalitis in humans after nasal exposure to contaminated water. Other Naegleria species are nonpathogenic and commonly used in research. Most Percolozoa are not known to infect humans.

Percolozoa is a clade within Excavata; its exact relationships to other excavate lineages have varied with analyses, and the group is defined largely by genetic data in combination with observed life-cycle features rather than a single morphology. The internal classification includes several lineages, with Naegleria representing the best-studied member.