Bacteria
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Bacteria
Temporal range: Archean or earlier – Recent
Scanning electron micrograph of Escherichia coli bacilli
Scientific classification
Domain:
Bacteria
Woese et al., 1990
Phyla
Gram positive / no outer membraneActinobacteria (high-G+C)
Firmicutes (low-G+C)
Tenericutes (no wall)*Gram negative / outer membrane presentAquificae
Bacteroidetes/Fibrobacteres–Chlorobi (FCB group)
Deinococcus-Thermus
Fusobacteria
Gemmatimonadetes
Nitrospirae
Planctomycetes–Verrucomicrobia/Chlamydiae (PVC group)
Proteobacteria
Spirochaetes
Synergistetes*Unknown / ungroupedAcidobacteria
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Dictyoglomi
Thermodesulfobacteria
Thermotogae
Synonyms
Eubacteria Woese & Fox, 1977
Bacteria (i/bæk't??ri?/; singular: bacterium) 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, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. They are also known to have flourished in manned spacecraft.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, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in recycling nutrients, with many of the stages in nutrient cycles dependent on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. In the biological communities surrounding hydrothermal vents and cold seeps, bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. On 17 March 2013, researchers reported data that suggested bacterial life forms thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest part of the Earth's oceans. 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. According to one of the researchers, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are."Most bacteria have not been characterized, and only about half of the phyla of bacteria have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.There are approximately ten times as many bacterial cells in the human flora as there are human cells in the body, with the largest number of the human flora being in the gut flora, and a large number on the skin. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, and some are beneficial. 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. 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, and the recovery of gold, palladium, copper and other metals in the mining sector, as well as in biotechnology, and the manufacture of antibiotics and other chemicals.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.
^ a b Woese CR, Kandler O, Wheelis ML (1990). "Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya". Proceedings of the National Academy of Sciences of the United States of America 87 (12): 4576–9. Bibcode:1990PNAS...87.4576W. doi:10.1073/pnas.87.12.4576. PMC 54159. PMID 2112744.
^ "Bacteria (eubacteria)". Taxonomy Browser, US National Institute of Health. Retrieved 10 September 2008.
^ Cite error: The named reference Woese1977 was invoked but never defined (see the help page).
^ Fredrickson JK, Zachara JM, Balkwill DL, Kennedy D, Li SM, Kostandarithes HM, Daly MJ, Romine MF, Brockman FJ (2004). "Geomicrobiology of high-level nuclear waste-contaminated vadose sediments at the Hanford site, Washington state". Applied and Environmental Microbiology 70 (7): 4230–41. doi:10.1128/AEM.70.7.4230-4241.2004. PMC 444790. PMID 15240306.
^ http://science.nasa.gov/science-news/science-at-nasa/2007/11may_locad3/
^ Whitman WB, Coleman DC, Wiebe WJ (1998). "Prokaryotes: the unseen majority". Proceedings of the National Academy of Sciences of the United States of America 95 (12): 6578–83. Bibcode:1998PNAS...95.6578W. doi:10.1073/pnas.95.12.6578. PMC 33863. PMID 9618454.
^ C.Michael Hogan. 2010. Bacteria. Encyclopedia of Earth. eds. Sidney Draggan and C.J.Cleveland, National Council for Science and the Environment, Washington DC
^ a b c Choi, Charles Q. (17 March 2013). "Microbes Thrive in Deepest Spot on Earth". LiveScience. Retrieved 17 March 2013.
^ Glud R, Wenzhöfer F, Middelboe M, Oguri K, Turnewitsch R, Canfield DE, Kitazato H (2013). "High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth". Nature Geoscience 6 (4): 284–288. Bibcode:2013NatGe...6..284G. doi:10.1038/ngeo1773.
^ Oskin, Becky (14 March 2013). "Intraterrestrials: Life Thrives in Ocean Floor". LiveScience. Retrieved 17 March 2013.
^ Rappé MS, Giovannoni SJ (2003). "The uncultured microbial majority". Annual Review of Microbiology 57: 369–94. doi:10.1146/annurev.micro.57.030502.090759. PMID 14527284.
^ Sears CL (2005). "A dynamic partnership: celebrating our gut flora". Anaerobe 11 (5): 247–51. doi:10.1016/j.anaerobe.2005.05.001. PMID 16701579.
^ "2002 WHO mortality data". Retrieved 20 January 2007.
^ "Metal-Mining Bacteria Are Green Chemists". Science Daily. 2 September 2010.
^ Ishige T, Honda K, Shimizu S (2005). "Whole organism biocatalysis". Current Opinion in Chemical Biology 9 (2): 174–80. doi:10.1016/j.cbpa.2005.02.001. PMID 15811802.
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