Microbiology refers to the study of microorganisms. As the name suggests,
microorganisms are organisms that are so small they can only be seen using
a microscope. Bacteria, fungi (such as yeasts and molds), protozoa, viruses,
algae, and some parasites are all types of microorganisms. Some people also
list prions as microorganisms even though they are proteins and not actually
organisms. (You may remember that prions are the cause of bovine spongiform
encephalopathy [BSE] and its human variation, Variant Creutzfeldt-Jakob
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