mi·​cro·​or·​gan·​ism | \ ˌmī-krō-ˈȯr-gə-ˌni-zəm How to pronounce microorganism (audio) \

Definition of microorganism

: an organism (such as a bacterium or protozoan) of microscopic or ultramicroscopic size

Examples of microorganism in a Sentence

Recent Examples on the Web But the Florida Fish and Wildlife Conservation Commission says Karenia brevis, the microorganism responsible for red tide, was not identified until 1946. Arthur Brice, CNN, 24 May 2021 There’s no large-scale research specifically answering this question, but both experts recommend changing out your towels about once a week to avoid excessive microorganism growth. Jessica Toscano, SELF, 13 May 2021 Sediment cores collected from different sites of the Bay of Brest (northeast Atlantic-English Channel, France) allowed scientists to reconstruct how marine microorganism communities changed in the last 5,000 years. David Bressan, Forbes, 27 Apr. 2021 But regulations set by the National Sanitation Foundation required them to periodically monitor the temperature of the product to make sure their machine wasn’t selling putrid refrozen yogurt full of the wrong sort of microorganism. Andy Greenberg, Wired, 20 Apr. 2021 Improper monitoring or setup can lead to microorganism or algae growth and the spread of disease. Angela Watson, chicagotribune.com, 26 Mar. 2021 The nature of this process has long been a mystery, which has fueled speculation that some microorganism may be producing methane the way bacteria do on Earth. Davide Castelvecchi, Scientific American, 16 Dec. 2010 These proteins can bind to the spike protein found on the novel coronavirus’s exterior and block the microorganism from entering human cells. Chris Smith, BGR, 10 Mar. 2021 Brown materials have lots of carbon but not enough nitrogen to allow the microorganism to rapidly decompose them. Dan Gill, NOLA.com, 18 Nov. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'microorganism.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of microorganism

1880, in the meaning defined above

History and Etymology for microorganism

International Scientific Vocabulary

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Time Traveler for microorganism

Time Traveler

The first known use of microorganism was in 1880

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Statistics for microorganism

Last Updated

5 Jun 2021

Cite this Entry

“Microorganism.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/microorganism. Accessed 12 Jun. 2021.

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English Language Learners Definition of microorganism

biology : an extremely small living thing that can only be seen with a microscope


mi·​cro·​or·​gan·​ism | \ ˌmī-krō-ˈȯr-gə-ˌni-zəm How to pronounce microorganism (audio) \

Kids Definition of microorganism

: a living thing (as a bacterium) that can only be seen with a microscope


mi·​cro·​or·​gan·​ism | \ -ˈȯr-gə-ˌniz-əm How to pronounce microorganism (audio) \

Medical Definition of microorganism

: an organism of microscopic or ultramicroscopic size

More from Merriam-Webster on microorganism

Nglish: Translation of microorganism for Spanish Speakers

Britannica.com: Encyclopedia article about microorganism


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