bac·​te·​ria | \ bak-ˈtir-ē-ə How to pronounce bacteria (audio) \

Definition of bacteria

plural of bacterium

diseases caused by bacteria Overprescribing antibiotics can contribute to the development of antibiotic-resistant bacteria.— Maanvi Singh

Note: Microscopic single-celled organisms lacking a distinct nucleus are known as bacteria. They may be shaped like spheres, rods, or spirals. They inhabit virtually all environments, including soil, water, organic matter, and the bodies of animals. Many bacteria swim by means of long whiplike structures called flagella. The DNA of most bacteria is found in a single, circular chromosome, and is distributed throughout the cytoplasm rather than contained within a membrane-enclosed nucleus. Though some bacteria can cause food poisoning and infectious diseases in humans, most are harmless and many are beneficial. They are used in various industrial processes, especially in the food industry (for example, in the production of yogurt, cheeses, and pickles).

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Is bacteria singular or plural?: Usage Guide

In its established and uncontroversial uses, bacteria is the plural of bacterium. … many of the bacteria isolated from these deep environments are anaerobic … — Stephen Jay Gould In speech and in some, typically nontechnical, journalistic writing, it also occurs in a singular sense, synonymous with bacterium. Lyme disease is a potentially serious arthritis-like ailment caused by a bacteria borne by certain tiny ticks. The Wall Street Journal … this bacteria is closely associated with poor health and, in old people, frailty … — Leah Hardy Although the singular use of bacteria is often identified as an error to be avoided, it is common in published writing. The plural form bacterias is also seen but is relatively rare. The bacteria seems to prefer living in water and is more resistant to chlorine and elevated water temperatures than other bacterias. — Allan Bruckheim

Examples of bacteria in a Sentence

Recent Examples on the Web Your first instinct might be to use a Clorox wipe, which promises to kill 99.99 percent of household germs and bacteria. Courtney Linder, Popular Mechanics, "Your Phone Is a Cesspool of Germs. Here's How to Actually Clean It," 4 Mar. 2020 For any family whose many hands come together from different places, the HomeSoap can act as a gatekeeper to reduce germs and bacteria in the house. Jessica Migala, NBC News, "Best UV light sanitizers for your smartphone and other devices 2020," 22 Jan. 2020 Just lock the cover over your brush and the UV light reportedly kills 99 percent of germs and bacteria in a few minutes. Popular Science, "Four UV sanitizers for a cleaner phone, toothbrush, or makeup kit," 2 Jan. 2020 The yeast and bacteria have evolved a form of metabolic cooperation. Henry Fountain, New York Times, "No Yeast at the Store? No Problem. It’s Everywhere in Your Home.," 7 May 2020 To help hotels reopen, Xenex Disinfection Services LLC has converted technology developed to rid hospital wards of viruses, germs and bacteria into a hotel housekeeping robot. Angus Loten, WSJ, "Travel Industry Automates Pandemic Response With New Digital Tools," 1 May 2020 The Centers for Disease Control and Prevention recommends the alcohol level in hand sanitizer be at least 60% to effectively kill common germs and bacteria, but most brands tend to add a little extra for good measure. Talia Abbas, Glamour, "Here’s Exactly Where to Buy Hand Sanitizer That Won’t Dry Out Your Hands," 27 Apr. 2020 The best and most recommended way to prevent the spread of germs and bacteria is to wash your hands. Leah Prinzivalli, Allure, "The 25 Best Hand Sanitizers to Clean Hands in a Pinch," 24 Apr. 2020 The mixture relies on natural yeast and bacteria present in the air and on a baker's hands to ferment. David Lindquist, Indianapolis Star, "Baking in the time of coronavirus: Bread is hot topic at home and away," 16 Apr. 2020

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

1864, in the meaning defined above

History and Etymology for bacteria

plural of bacterium

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Time Traveler for bacteria

Time Traveler

The first known use of bacteria was in 1864

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Statistics for bacteria

Last Updated

28 May 2020

Cite this Entry

“Bacteria.” Dictionary, Merriam-Webster, Accessed 4 Jun. 2020.

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More Definitions for bacteria


Medical Definition of bacteria

 (Entry 1 of 2)

plural of bacterium


bac·​te·​ria | \ bak-ˈtir-ē-ə How to pronounce bacteria (audio) \

Medical Definition of bacteria (Entry 2 of 2)

1 : bacterium not usually used technically caused by a bacteria borne by certain tiny ticksWall Street Journal a single bacteria—there are roughly 200 in each cough—apparently can infect a person— Cheryl Clark
2 plural capitalized : a domain in the system of classification dividing all organisms into three major domains of life that includes the prokaryotes that are bacteria but not those that are archaebacteria or archaea — compare eubacteria

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More from Merriam-Webster on bacteria

Rhyming Dictionary: Words that rhyme with bacteria

Spanish Central: Translation of bacteria

Nglish: Translation of bacteria for Spanish Speakers

Britannica English: Translation of bacteria for Arabic Speakers Encyclopedia article about bacteria

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