Source:http://linkedlifedata.com/resource/umls/id/C0445623
NCI: An organism that can be seen only through a microscope. Microorganisms include bacteria, protozoa, algae, and fungi. Although viruses are not considered living organisms, they are sometimes classified as microorganisms.,CSP: organism of microscopic or ultramicroscopic size.,NCI: A microscopic organism. The term microorganism may refer to a prokaryote or eukaryote, and may be a unicellular or multicellular organism. All taxonomic kingdoms contain microorganisms.,HL7V3.0: <p>All single celled living organisms including protozoa, bacteria, yeast, viruses, etc.</p>