Amoeba protozoan. Light microscopy footage of an Amoeba proteus protozoan moving in water. This is a freshwater single_celled organism that feeds on bacteria and smaller protozoa. It uses pseudopodia cytoplasmic extensions to engulf its food and for locomotion. The most prominent features are its nucleus dark, vacuoles containing food also dark, and a large contractile vacuole round, centre. This is a large amoeba, ranging in size from 220 to 740 micrometres.