Amoebae

A common name for various unicellular, usually microscopic organisms of the order Amoebida, found in fresh and salt water, moist soil, and as parasites of humans and animals. They are defined by their shapeshifting: they move and feed by extruding pseudopodia, temporary projections of the cell. Most amoebae are harmless environmental grazers on bacteria, but a few are dangerous pathogens — Entamoeba histolytica causes amoebic dysentery, Naegleria fowleri causes fatal brain infection. In food and water safety, the hardy cysts of pathogenic species matter most: they survive chlorination better than many bacteria, so filtration and protected sources are key defences.