unicellular organisms or protozoa, single-celled organisms microorganisms such as archaea, bacteria or protists swim in water

algae amoeba bacteria bacterial bacteriological bacteriology bacterium biological biology cell close colored contagion contamination contractile digestive disease ecosystem environment flora germ infection life medical membrane micro biota microbe microbiology microorganism microscope microscopic microscopy nature nucleus organism plankton primitive protist protists protozoa protozoan 039 protozoans single singlecelled unicellular water zoology organisms microorganisms archaea swim generated