bacterium

noun
bac·​te·​ri·​um | \ bak-ˈtir-ē-əm How to pronounce bacterium (audio) \
plural bacteria\ bak-​ˈtir-​ē-​ə How to pronounce bacteria (audio) \

Definition of bacterium

biology : any of a domain (Bacteria) (see domain sense 8) of chiefly round, spiral, or rod-shaped single-celled prokaryotic microorganisms that typically live in soil, water, organic matter, or the bodies of plants and animals, that make their own food especially from sunlight or are saprophytic or parasitic, are often motile by means of flagella, reproduce especially by binary fission, and include many important pathogens broadly : prokaryote

Note: Bacteria lack a nuclear membrane or membrane-bound organelles and are categorized as gram-positive or gram-negative when a cell wall is present. While many bacteria are aerobic requiring the presence of oxygen to survive, others are anaerobic and are able to survive only in the absence of oxygen.

— compare archaea, eukaryote

Examples of bacterium in a Sentence

Recent Examples on the Web

These mini-donut-sized Mosquito Dunks contain BTI, a bacterium that's lethal to mosquito larvae, black flies and fungus gnats for up to 30 days, but won't harm plants or animals (including humans). Los Angeles Times, "Pollinators & predators in your garden: How to save one, kill the other," 17 July 2019 The main reason to do that is to cure a devastating, diarrhea-causing infection by Clostridioides difficile, the bacterium usually known as C. diff (and formerly called Clostridium difficile). Maryn Mckenna, WIRED, "The Death of a Patient and the Future of Fecal Transplants," 11 July 2019 The infection is caused by the bacterium Mycoplasma gallisepticum, which is common in domestic turkeys and chickens. Joan Morris, The Mercury News, "Contagious house finch eye disease reported in Walnut Creek area," 17 June 2019 The bacterium behind the outbreak was a particularly nasty strain of Shiga toxin-producing Escherichia coli O157:H7 that produces only Shiga toxin type 2 (Stx2), the more toxic of two types of toxins E. coli tends to carry. Beth Mole, Ars Technica, "The poop of 100K cows may be to blame for that deadly romaine E. coli outbreak," 8 Aug. 2018 Each individual bacterium has a genome with roughly 4,200 to 5,600 genes. Quanta Magazine, "Researchers Rethink the Ancestry of Complex Cells," 9 Apr. 2019 The bacterium didn't show signs of resistance, even after three weeks of exposure. Sarah Kaplan, ajc, "Scientists discover potentially powerful new antibiotic in dirt," 13 Feb. 2018 This is an environmental bacterium and opportunistic pathogen. Beth Mole, Ars Technica, "Meet “raw” water—ludicrously priced unfiltered water with random bacteria," 3 Jan. 2018 The aggressive bacterium was dubbed Enterobacter bugandensis after the hospital where it was found. Jill Kiedaisch, Popular Mechanics, "Drug-Resistant Space Bugs Found Aboard the ISS," 28 Nov. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'bacterium.' 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 bacterium

1835, in the meaning defined above

History and Etymology for bacterium

New Latin, from Greek baktērion staff

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Statistics for bacterium

Last Updated

23 Jul 2019

Look-up Popularity

Time Traveler for bacterium

The first known use of bacterium was in 1835

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More Definitions for bacterium

bacterium

noun

English Language Learners Definition of bacterium

: any one of a group of very small living things that often cause disease

bacterium

noun
bac·​te·​ri·​um | \ bak-ˈtir-ē-əm How to pronounce bacterium (audio) \
plural bacteria\ -​ē-​ə \

Kids Definition of bacterium

: any of a group of single-celled microscopic organisms that are important to humans because of their chemical activities and as causes of disease

bacterium

noun
bac·​te·​ri·​um | \ bak-ˈtir-ē-əm How to pronounce bacterium (audio) \
plural bacteria\ -​ē-​ə How to pronounce bacteria (audio) \

Medical Definition of bacterium

: any of a domain (Bacteria) of prokaryotic round, spiral, or rod-shaped single-celled microorganisms that may lack cell walls or are gram-positive or gram-negative if they have cell walls, that are often aggregated into colonies or motile by means of flagella, that typically live in soil, water, organic matter, or the bodies of plants and animals, that are usually autotrophic, saprophytic, or parasitic in nutrition, and that are noted for their biochemical effects and pathogenicity broadly : prokaryote

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More from Merriam-Webster on bacterium

Rhyming Dictionary: Words that rhyme with bacterium

Spanish Central: Translation of bacterium

Nglish: Translation of bacterium for Spanish Speakers

Britannica English: Translation of bacterium for Arabic Speakers

Britannica.com: Encyclopedia article about bacterium

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