∞ generated and posted on 2015.12.30 ∞

Living thing that, as a fully mature individual, is too small to be seen without magnification.

Microorganisms include all of the prokaryotes, a majority of the single-cell eukaryotes, numerous small, colonial eukaryotes, and the viruses as well as minimalist virus-like entities known as viroids.

Most microorganisms are either single celled or acellular. Microorganisms include prokaryotes, most single-celled eukaryotes, viruses, and viroids. Animals strictly are not microorganisms though many are so small as to arguably qualify.

What is the relevance of microorganisms?

The infectious roteins called prions are not microorganisms because they are not organisms, even as loosely defined. They are, however, "micro", that is, quite small. Similarly, components of individual cells are not microorganisms, not even conjugative plasmids even though the latter are both infectious and DNA based. Lastly, the juvenile stages of macroorganisms are generally not considered to be microorganisms, even if they individually are rather small.

Some microorganisms actually are large enough, barely, to be seen with the naked eye, while some macroorganisms are awfully small. Though microorganisms that are pathogens receive a great deal of attention, in fact most microorganisms are not pathogenic.

The following is a(n extremely incomplete) list of various types and taxa of microorganisms:

Acid fast, Acinetobacter, Algae, Bacillus, Bacteria, Bacteriophage, Bacteroides, Bdellovibrio, Beta-hemolytic streptococci, Bordetella, Borrelia, Burkholderia, Campylobacter, Candida, Candida albicans, Chlamydia, Clostridium, Clostridium botulinum, Clostridium difficile, Clostridium perfringens, Clostridium tetani, Coliforms, Corynebacterium, Cyanobacteria, Enterics, Enterobacter, Enterococcus, Escherichia, Family Enterobacteriaceae, Fusobacterium, Gardnerella, Giardia, Green bacteria, Green nonsulfur bacteria, Haemophilus, Helicobacter, Klebsiella, Lactobacillus, Legionella, Leptospira, Listeria, Microorganism, Moraxella, Mold, Mycobacterium, Mycoplasma, Neisseria, Non-beta-hemolytic streptococci, Pasteurella, Plasmodium, Prokaryote, Propionibacterium, Proteobacteria, Proteus, Pseudomonas, Purple bacteria, Purple nonsulfur bacteria, Rhizobia, Rickettsia, Saccharomyces, Salmonella, Serratia, Shigella, Staphylococcus, Streptococcus, Streptomyces, Treponema, Trichomonas, Trichomonas vaginalis, Vibrio, Virus, Yeast, Yersinia