Bacteria

Bacteria
Temporal range: Archean or earlier – present
EscherichiaColi NIAID.jpg
Scanning electron micrograph of Escherichia coli rods
Scientific classification e
Domain:Bacteria
Woese, Kandler & Wheelis, 1990[1]
Phyla
Synonyms
Eubacteria Woese & Fox, 1977[3]

Bacteria (ə/ (About this soundlisten); common noun bacteria, singular bacterium) are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste,[4] and the deep biosphere of the earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory (specifically unculturable phyla, known as candidate phyla, make up 103 out of approximately 142 known phyla).[5] The study of bacteria is known as bacteriology, a branch of microbiology.

Virtually all animal life on earth is dependent on bacteria for their survival as only bacteria and some archea possess the genes and enzymes necessary to synthesize vitamin B12, also known as cobalamin, and provide it through the food chain. Vitamin B12 is a water-soluble vitamin that is involved in the metabolism of every cell of the human body. It is a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism. It is particularly important in the normal functioning of the nervous system via its role in the synthesis of myelin.[6][7][8][9]

There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth,[10] forming a biomass which exceeds that of all plants and animals.[11] Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process.[12] In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Data reported by researchers in October 2012 and published in March 2013 suggested that bacteria thrive in the Mariana Trench, which, with a depth of up to 11 kilometres, is the deepest known part of the oceans.[13][14] Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States.[13][15] According to one of the researchers, "You can find microbes everywhere—they're extremely adaptable to conditions, and survive wherever they are."[13]

The famous notion that bacterial cells in the human body outnumber human cells by a factor of 10:1 has been debunked. There are approximately 39 trillion bacterial cells in the human microbiota as personified by a "reference" 70 kg male 170 cm tall, whereas there are 30 trillion human cells in the body. This means that although they do have the upper hand in actual numbers, it is only by 30%, and not 900%.[16]

The largest number exist in the gut flora, and a large number on the skin.[17] The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial, particularly in the gut flora. However, several species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, leprosy, and bubonic plague. The most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year, mostly in sub-Saharan Africa.[18] In developed countries, antibiotics are used to treat bacterial infections and are also used in farming, making antibiotic resistance a growing problem. In industry, bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium, copper and other metals in the mining sector,[19] as well as in biotechnology, and the manufacture of antibiotics and other chemicals.[20]

Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea.[1]

Other Languages
Acèh: Bakteri
Afrikaans: Bakterie
Alemannisch: Bakterien
አማርኛ: ባክቴሪያ
العربية: بكتيريا
aragonés: Eubacteria
অসমীয়া: বেক্টেৰিয়া
asturianu: Bacteria
Avañe'ẽ: Pokokaku'i
Aymar aru: Jisk'a laq'u
azərbaycanca: Bakteriyalar
تۆرکجه: باکتری
Bân-lâm-gú: Sè-khún
башҡортса: Бактериялар
беларуская: Бактэрыі
беларуская (тарашкевіца)‎: Бактэрыі
български: Бактерии
bosanski: Bakterija
brezhoneg: Bakteri
буряад: Нян
català: Eubacteris
Чӑвашла: Бактерисем
čeština: Bakterie
Cymraeg: Bacteria
dansk: Bakterier
Deutsch: Bakterien
ދިވެހިބަސް: ބެކްޓީރިޔާ
eesti: Bakterid
Ελληνικά: Βακτήριο
español: Bacteria
Esperanto: Bakterioj
estremeñu: Bateria
euskara: Bakterio
فارسی: باکتری
Fiji Hindi: Bacteria
føroyskt: Bakteria
français: Bactérie
Frysk: Baktearje
Gaeilge: Baictéir
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galego: Bacterias
Gĩkũyũ: Bacteria
客家語/Hak-kâ-ngî: Se-khiûn
한국어: 세균
հայերեն: Բակտերիաներ
हिन्दी: जीवाणु
hornjoserbsce: Bakterije
hrvatski: Bakterije
Ilokano: Bakteria
Bahasa Indonesia: Bakteri
interlingua: Bacterio
íslenska: Gerlar
italiano: Bacteria
עברית: חיידקים
Jawa: Baktèri
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қазақша: Бактериялар
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Kreyòl ayisyen: Bakteri
kurdî: Bakterî
Кыргызча: Бактерия
Latina: Bacterium
latviešu: Baktērijas
Lëtzebuergesch: Bakterien
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lietuvių: Bakterijos
Ligure: Bacteria
Limburgs: Bacterië
Lingua Franca Nova: Bateria
Luganda: Bakitiiriya
lumbaart: Bacteria
magyar: Baktériumok
македонски: Бактерии
मराठी: जीवाणू
Bahasa Melayu: Bakteria
Minangkabau: Bakteri
Mìng-dĕ̤ng-ngṳ̄: Sá̤-kṳ̄ng
монгол: Нян
မြန်မာဘာသာ: ဘက်တီးရီးယား
Nederlands: Bacteriën
नेपाल भाषा: ब्याक्टेरिया
日本語: 細菌
Napulitano: Bacteria
Nordfriisk: Bakteerien
norsk: Bakterier
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occitan: Bactèri
oʻzbekcha/ўзбекча: Bakteriyalar
ਪੰਜਾਬੀ: ਬੈਕਟੀਰੀਆ
پنجابی: بیکٹیریا
Papiamentu: Bakteria
پښتو: باکټريا
Patois: Baktiiria
Plattdüütsch: Bakterien
polski: Bakterie
português: Bactérias
Qaraqalpaqsha: Bakteriya
română: Bacterie
Runa Simi: Añaki
русиньскый: Бактерії
русский: Бактерии
саха тыла: Бактериялар
संस्कृतम्: जीवाणुः
Scots: Bacteria
shqip: Bacteria
sicilianu: Batteriu
Simple English: Bacteria
slovenčina: Baktérie
slovenščina: Bakterije
Soomaaliga: Bakteriya
کوردی: بەکتریا
српски / srpski: Бактерија
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Türkçe: Bakteri
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Vahcuengh: Sigin
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Volapük: Bakter
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中文: 细菌
kriyòl gwiyannen: Baktéri