bacterium

noun

bac·te·ri·um | \ bak-ˈtir-ē-əm

plural bacteria\ bak-ˈtir-ē-ə

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

After eliminating sources of contamination, the researchers found just one type of bacterium: Streptococcus agalactiae. — Juanita Bawagan, Science | AAAS, "Babies get critical gut bacteria from their mother at birth, placenta study suggests," 31 July 2019 In the real world, live bacteria can multiply, creating more of their own type of bacterium. — Svenja Lohner, Scientific American, "How Do You Stop Superbugs?," 4 July 2019 When a bacterium is killed by a viral infection, its cell wall explodes. — Jonathan Lambert, WIRED, "Scientists Discover Nearly 200,000 Kinds of Ocean Viruses," 28 Apr. 2019 When a bacterium is killed by a viral infection, its cell wall explodes. — Quanta Magazine, "Scientists Discover Nearly 200,000 Kinds of Ocean Viruses," 25 Apr. 2019 Participating neighborhoods are sprayed with a special tick-killing fungus, or dotted with bait boxes that trap tiny mammals, like white-footed mice, from which ticks acquire the Lyme bacterium. — Micah Hauser, The New Yorker, "Tickbusters on the Lookout for Lyme," 22 July 2019 Also, drug therapies that target toxic proteins released in the brain by bacterium may slow or halt the progression of Alzheimer’s. — Cindy Krischer Goodman, sun-sentinel.com, "New clues about why people get Alzheimer’s and how to fight it," 19 July 2019 The bacterium then uses these chemicals as food sources. — The Economist, "An enzyme that digests plastic could boost recycling," 16 Apr. 2018 Inside the insect, the bacterium releases a protein that causes the pest to die within a few days. — The Editors Of Organic Life, Good Housekeeping, "The 7 Best Organic Pest Control Techniques For Your Garden," 18 Dec. 2017

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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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

See the full definition for bacterium in the English Language Learners Dictionary

bacterium

noun

bac·te·ri·um | \ bak-ˈtir-ē-əm

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

plural bacteria\ -ē-ə

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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bacterium

Definition of bacterium

Examples of bacterium in a Sentence

First Known Use of bacterium

History and Etymology for bacterium

English Language Learners Definition of bacterium

Kids Definition of bacterium

Medical Definition of bacterium

bacterium

Definition of bacterium

Examples of bacterium in a Sentence

First Known Use of bacterium

History and Etymology for bacterium

English Language Learners Definition of bacterium

Kids Definition of bacterium

Medical Definition of bacterium

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