microorganism

[mahy-kroh-awr-guh-niz-uhm]

noun

1. any organism too small to be viewed by the unaided eye, as bacteria, protozoa, and some fungi and algae.

microorganism

/ ˌmaɪkrəʊˈɔːɡəˌnɪzəm /

noun

1. any organism, such as a bacterium, protozoan, or virus, of microscopic size

microorganism

1. An organism that can be seen only with the aid of a microscope and that typically consists of only a single cell. Microorganisms include bacteria, protozoans, and certain algae and fungi.

2. See Note at germ

Other Word Forms

• microorganic adjective
• microorganismal adjective

Word History and Origins

Origin of microorganism¹

First recorded in 1875–80; micro- + organism

Example Sentences

In this study, the researchers measured the nitrogen isotopic composition in corals to infer how much nitrogen microorganisms have fixed over the past 120 years.

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While genetics and lifestyle factors clearly affect a person's heart health, scientists are discovering that microorganisms living in the gut may also have an important influence.

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This indicates that microorganisms are likely the main force behind this transformation in natural environments.

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Building on their findings, Kumawat and his colleagues now plan to cultivate these microorganisms in controlled incubators to learn more about how they obtain nutrients and persist in such inhospitable environments.

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The discovery highlights a growing evolutionary response: microorganisms are adapting to human pollution on a planetary scale.

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Related Words

• bacterium 
• microbe 
• pathogen 
• virus