amoebae

Amoebae are a diverse group of single-celled eukaryotes characterized by amoeboid movement and feeding through pseudopodia. They belong to the clade Amoebozoa and are found in a wide range of habitats, including soils, freshwater, and marine environments. Most amoebae are free-living, but some species are parasitic or opportunistic pathogens.

Morphology and biology: Amoebae have a flexible cell surface and typically lack a rigid cell wall. Their cytoplasm is differentiated into an outer clear ectoplasm and an inner granular endoplasm. They move by extending and retracting pseudopodia, a mode of locomotion known as amoeboid movement. Nutrients are acquired by phagocytosis, with food vacuoles forming as digestion proceeds. Many species form cysts under unfavorable conditions to survive drying or food scarcity.

Reproduction and life cycle: Reproduction is usually asexual, occurring by binary fission, though some species may engage in multiple fission or limited sexual processes that are not fully understood. Encystment and excystment enable persistence in variable environments and during transmission between hosts.

Ecology and human relevance: Amoebae are important grazers of bacteria and contribute to nutrient cycling in microbial food webs. A few species are pathogenic to humans or animals, notably Entamoeba histolytica (intestinal amebiasis), Naegleria fowleri (primary amebic meningoencephalitis), and Acanthamoeba spp. (keratitis and, rarely, CNS infections). Diagnosis and treatment depend on the species and clinical presentation.