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

Definition of bacteria

: bacterium not usually used technically

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Is bacteria singular or plural?: Usage Guide

Bacteria is regularly a plural in scientific and pedagogical use; in speech and in journalism it is also used as a singular, and it is sometimes pluralized as bacterias. caused by a bacteria borne by certain tiny ticks Wall Street Journal more resistant to chlorine and elevated water temperatures than other bacterias — Allan Bruckheim, M.D., Chicago Tribune These journalistic uses are found in British as well as American sources.

Did You Know?

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 whip-like 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).

Examples of bacteria in a Sentence

Recent Examples on the Web

The Orange County Fair is enhancing its sanitation practices in livestock areas in light of the death of a young boy who possibly picked up a virulent strain of the E. coli bacteria from a petting zoo last month at the San Diego County Fair. Hillary Davis,, "O.C. Fair emphasizes hand-washing after child illnesses and death linked to animals at San Diego County Fair," 1 July 2019 Blue Water Baltimore collects water quality samples from different locations of the Baltimore harbor to test for bacteria level. Scott Dance,, "Sampling initiative in Baltimore's Inner Harbor aims to answer the question, 'How's the water, hon?'," 25 June 2019 The organization monitors bacteria levels in the water that exceed the acceptable standards established by the Environmental Protection Agency (EPA), the Texas General Land Office (GLO). Peter Dawson, Houston Chronicle, "See which Houston-area beaches currently have dangerous fecal matter levels, per government readings," 21 June 2019 It was also manufactured by ADM Milling Co. As King Arthur Flour itself put it in a press release about the recall, E. coli bacteria can cause a nasty bout of illness, or in more vulnerable populations, kidney damage or death. Zoë Schlanger, Quartz, "Pillsbury’s flour recall serves as a devastating reminder that cookie dough is dangerous," 17 June 2019 The overall goal of the transplant is to restore a healthy balance of gut bacteria to the recipient, which C. diff takes away from them. Maggie O'neill,, "How Is a Fecal Transplant Done? Here’s Why the FDA is Now Warning Patients About Them," 17 June 2019 Baard Espeli, deputy mayor of the municipality of Askoey, an island north of Bergen, says the E. coli bacteria that can cause gastrointestinal illness was found in a pool that supplied part of the drinking water. Fox News, "Source for water contamination in Norway not yet found," 11 June 2019 Se Jin Song, a biologist at the University of California San Diego and the study’s lead author, had previously studied the convergent evolution of gut bacteria. Joshua Sokol, New York Times, "The Vampire Birds of the Galápagos Have Fascinating Inner Lives," 8 June 2019 There also is the threat of rip currents, waves and undertows and recent thunderstorms with rainfall could cause high e-coli bacteria counts in the water. Gregory Tejeda, Post-Tribune, "Gary beaches open: New rules say children must be within arm's reach of an adult," 6 June 2019

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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Statistics for bacteria

Last Updated

10 Jul 2019

Look-up Popularity

Time Traveler for bacteria

The first known use of bacteria was in 1864

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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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