Definition of bacterium
biology : any of a domain (Bacteria) (see domain 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 ◆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
Recent Examples of bacterium from the Web
Around 1,600 people contract the bacterium annually and some 260 die from the infection, according to Centers for Disease Control and Prevention.
Botulism is a potent neurotoxin produced by the bacterium, Clostridium botulinum.
The herbivores frequently get the infection by eating grass or other plants that have been contaminated with Bacillus anthracis, a bacterium which can live for decades without a host.
Their investigation ultimately identified a bacterium, Legionella, for the first time associated with the hotel's air-conditioning system that triggered severe cases of pneumonia.
The man tested positive for Vibrio vulnificus, a bacterium commonly found in coastal ocean water.
Fasciation may be caused by mutation, virus, bacterial infection by bacterium known as Rhodococcus fascians, or injury to the meristem or growing part of the plant by insect, animal or human.
The bacterium that affected your citrus is not going to cause the decline of a fig.
In 2016, this bacterium was suddenly all over the news in Wisconsin.
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.
Origin and Etymology of bacterium
New Latin, from Greek baktērion staff
First Known Use: 1835See Words from the same year
BACTERIUM Defined for English Language Learners
Definition of bacterium for English Language Learners
: any one of a group of very small living things that often cause disease
BACTERIUM Defined for Kids
Definition of bacterium for Students
: any of a group of single-celled microscopic organisms that are important to humans because of their chemical activities and as causes of disease
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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