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Bacteria

One of three superkingdoms (domains) of cellular organisms, the others being Archaea and Eukarya. Bacteria are unicellular and anucleate i.e. prokaryotes. They embrace a great diversity of ...

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Oxford Dictionary of Biochemistry and Molecular Biology (2 ed.)

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Life Sciences
Length:
4 words

... plural of bacterium...

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A Dictionary of Genetics (8 ed.)

Reference type:
Subject Reference
Current Version:
2014
Subject:
Science and technology, Life Sciences
Length:
35 words

... in the broader sense, all prokaryotes; more specifically, organisms belonging to the subkingdom Bacteria. See Appendix A , superkingdom Prokaryotes; Appendix C , 1673, van Leeuwenhoek; Appendix F , Genome Sizes and Gene Numbers (of bacteria); Eubacteria...

Bacteria

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Oxford Dictionary of Biochemistry and Molecular Biology (2 ed.)

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Life Sciences
Length:
42 words

... one of three superkingdoms (domains) of cellular organisms, the others being Archaea and Eukarya. Bacteria are unicellular and anucleate i.e. prokaryotes . They embrace a great diversity of forms, major divisions including the Cyanobacteria, Proteobacteria (which includes Gram‐negative bacteria), and Gram‐positive bacteria...

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A Dictionary of Zoology (5 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Life Sciences
Length:
104 words

... A taxonomic kingdom comprising the subkingdoms Archaea and Eubacteria or, in the three- domain classification, the only kingdom in the domain Eubacteria. Bacteria are prokaryotes , most of which are single-celled and most having a rigid cell wall. They are almost universal in distribution and play many important roles as agents of decay and mineralization and in the recycling of elements such as nitrogen. Some species cause illness in animals. There are eleven principal groups: Gram-positive bacteria ( See Gram reaction ); purple bacteria; ...

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A Dictionary of Dentistry (2 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Medicine and health, Dentistry
Length:
140 words
Illustration(s):
1

... pl. n. ( sing. bacterium ) Small micro-organisms lacking a distinct nuclear membrane ( prokaryotes ), most of which are unicellular. Most bacteria come in one of three basic shapes: spherical, rod-shaped, or spiral. Spherical bacteria (cocci) may exist in pairs (diplococci), clumps (staphylococci, e.g. Staphylococcus aureus ) or chains (streptococci, e.g. Streptococcus mutans ). Rod-shaped bacteria (bacilli, e.g. Lactobacillus acidophilus ) can exist in chains (streptobacilli). Spiral bacteria may be curved or comma-shaped (vibrio), shaped as...

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World Encyclopedia

Reference type:
Subject Reference
Current Version:
2004
Subject:
Encyclopedias
Length:
121 words

... Simple, unicellular, microscopic organisms. They lack a clearly defined nucleus and most are without chlorophyll . Many are motile, swimming by means of whip-like flagella. Most multiply by fission . In adverse conditions, many can remain dormant inside highly resistant spores with thick protective coverings. Bacteria may be aerobic or anaerobic . Although pathogenic bacteria are a major cause of human disease, many bacteria are harmless or even beneficial to humans by providing an important link in food chains , by decomposing plant and animal...

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A Dictionary of Plant Sciences (4 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
258 words

... In taxonomy , a kingdom comprising 11 main groups of prokaryotes . These are: purple (photosynthetic); Gram positive ( see gram reaction ); cyanobacteria ; green non-sulphur; spirochaetes; flavobacteria; green sulphur; Planctomyces; Chalmydiales; Deinococci; and Thermatogales. Most bacteria are single-celled and most have a rigid cell wall . Cell division usually occurs by binary fission; mitosis never occurs. Bacteria are almost universal in distribution and may live as saprotrophs , parasites , symbionts , pathogens, etc. They have many...

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Fergus G Priest

The Oxford Companion to Beer

Reference type:
Subject Reference
Current Version:
2013

...beers. Some bacteria generate their energy by respiration, using oxygen as we do, or perhaps nitrate, which is reduced to nitrite in the process. Alternatively, they can ferment sugars in the absence of oxygen to produce, for example, lactic acid or ethanol. Some bacteria are restricted to respiration or fermentation, whereas others are more versatile and can switch between physiologies. In breweries, bacteria are largely seen as spoilage organisms. Bacteria associated with beer and breweries include acetic acid bacteria, lactic acid bacteria,...

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A Dictionary of Nursing (7 ed.)

Reference type:
Subject Reference
Current Version:
2017
Subject:
Medicine and health
Length:
129 words

...bacteria [bak- teer -iă] pl. n. ( sing. bacterium ) a group of microorganisms all of which lack a distinct nuclear membrane and most of which have a cell wall of unique composition. Most bacteria are unicellular; the cells may be spherical ( see coccus ), rodlike ( see bacillus ), spiral ( see Spirillum ), comma-shaped ( see Vibrio ), or corkscrew-shaped ( see spirochaete ). Generally, they range in size between 0.5 and 5 μ ‎m. Motile species bear one or more fine hairs (flagella) arising from their surface. Bacteria reproduce asexually by...

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A Dictionary of Biomedicine (2 ed.)

Reference type:
Subject Reference
Current Version:
2019

...Bacteria (formerly Eubacteria ) A major subdivision of the prokaryotes that includes most Gram-positive bacteria, cyanobacteria, mycoplasmas, enterobacteria, and pseudomonads. They are distinguished from the Archaea (formerly Archaebacteria) by the presence of ester-linked lipids in the cytoplasmic membrane, peptidoglycan in the cell wall, and the absence of introns . Some taxonomists still favour a two-domain classification (eukaryotes and prokaryotes) but the three-domain scheme (Eukaryota, Bacteria, and Archaea) is now generally accepted. Bacteria...

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A Dictionary of Biology (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
373 words
Illustration(s):
1

... (the archaea) and Bacteria. Defining characteristics of bacteria include the possession of cell walls containing peptidoglycan, and membrane lipids containing fatty acids in ester linkage to glycerol, whereas archaea lack peptidoglycan and have ether-linked lipids. However, in general parlance, the term ‘bacteria’ can still, erroneously, encompass both archaea and bacteria. Bacteria can be characterized in a number of ways, for example by their reaction with Gram’s stain , their GC content , or on the basis of their metabolic requirements (e.g. whether...

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A Dictionary of Geology and Earth Sciences (5 ed.)

Reference type:
Subject Reference
Current Version:
2020

...in the biosphere . Bacteria are also important to humans, e.g. as causal agents of certain diseases, as agents of spoilage of food and other commodities, and as useful agents in the industrial production of commodities such as vinegar, antibiotics, and many types of dairy products. The oldest fossils known are of bacteria, from rocks in S. Africa that are apparently 3200 million years old. These must have been heterotrophic bacteria, feeding off organic molecules dissolved in the oceans of that time. The first photosynthetic bacteria, of anaerobic type,...

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A Dictionary of Agriculture and Land Management

Reference type:
Subject Reference
Current Version:
2019
Subject:
Social sciences
Length:
102 words

... ( sing . bacterium ) The major group of microbes found within the prokaryotic organisms. An extremely diverse group of micro-organisms, it is possible to find examples of bacteria living in all ecological niches found on the planet, and they are thought to be one of the oldest forms of life on Earth. Whilst many are of no direct consequence to man or their activities, some are highly beneficial and a few are very damaging (i.e. pathogenic). In all their forms, the study of bacteria has led to many innovations that have directly improved the health...

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A Dictionary of Psychology (4 ed.)

Reference type:
Subject Reference
Current Version:
2015

... n. pl. Unicellular or threadlike micro-organisms that reproduce by fission ( 2 ) and are often parasitic and liable to cause diseases. bacterial adj . bacterium sing . [From Greek bakterion a little rod, diminutive of baktron a...

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The Oxford Companion to the Earth

Reference type:
Subject Reference
Current Version:
2003

...of plants, such as peas and beans, where bacteria develop in small nodules. These bacteria are fed by the plant, and in return they supply the plant with ammonia, an essential nutrient. The bacteria obtain this ammonia from nitrogen in air by nitrogen fixation , in a process unique to bacteria. Bacterial interactions with higher organisms are not, however, always benevolent, for some bacteria are major pathogens that cause a variety of diseases, some of which can be fatal. Fortunately, micro-organisms, including bacteria, have provided a source of antibotics...

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Concise Medical Dictionary (10 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Medicine and health, Clinical Medicine
Length:
224 words

...or resting form ( endospore ). Bacteria reproduce asexually by simple division of cells; incomplete separation of daughter cells leads to the formation of colonies consisting of different numbers and arrangements of cells. Some colonies are filamentous in shape, resembling those of fungi. Transfer of DNA from one bacterium to another takes place in the process of conjugation . Bacteria are very widely distributed. Some live in soil, water, or air; others are parasites of humans, animals, and plants. Many parasitic bacteria do not harm their hosts; some...

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A. Dinsmoor Webb, Richard Smart, and Patrick Williams

The Oxford Companion to Wine (4 ed.)

Reference type:
Subject Reference
Current Version:
2015

... , very small micro-organisms which have serious implications in both viticulture and winemaking. Although not common pathogens of the grapevine, bacterial diseases are potentially destructive and therefore very important. In winemaking just two groups of bacteria are important, acetobacter and lactic acid bacteria . Since grape juice and wine are both high in acidity , the great majority of bacteria, with the exception of these two groups, are incapable of living in them and, if introduced, do not survive. (Drinks such as cider, perry, orange...

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The Oxford Companion to Food (3 ed.)

Reference type:
Subject Reference
Current Version:
2014
Subject:
Society and culture, Cookery, Food, and Drink
Length:
1,254 words

...different types of bacteria is the spoilage of unpasteurized milk. At room temperature, mesophilic bacteria turn milk sugar to lactic acid so that the milk goes sour. In a refrigerator these organisms are repressed; instead, psychrophilic bacteria attack the milk protein and turn the milk alkaline and smelly. Only heating well above their preferred temperature, or antiseptic chemicals, can kill bacteria. Chilling, even freezing, or drying causes them to stop growing; but when warmth or moisture return they at once start again. Some bacteria which themselves are...

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A Dictionary of Epidemiology (6 ed.)

Reference type:
Subject Reference
Current Version:
2016

...Bacteria (singular: bacterium) Single-celled prokaryotic Microorganisms found throughout nature, which can be beneficial or cause disease. One of two major types of prokaryotic (lacking a nucleus) single-celled organisms. Large numbers of bacteria and bacterial species are found in the human digestive system or on the skin. Epidemiology and medical microbiology through the 19th and 20th centuries focused on bacterially caused diseases as tuberculosis, typhoid, and cholera. More recently, there has been interest on issues such as the ecology of...

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A Dictionary of the Internet (4 ed.)

Reference type:
Subject Reference
Current Version:
2019

... Forms of virus . A term used to describe programs which replicate themselves and then usually start executing, carrying out some processor- or memory-intensive task such as reading from a file. Each replicated virus then reproduces itself again. Eventually, the number of these viruses reaches the point where the computer is unable to cope with their demands and crash es or exhibits extremely sluggish...

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