Bacteria - Wikipedia Page 1 of 33 Bacteria From Wikipedia, the free encyclopedia Bacteria ( i/bækˈtɪəriə/; common noun bacteria, singular bacterium) constitute a large domain of prokaryotic Bacteria microorganisms. Typically a few micrometres in length, Temporal range: bacteria have a number of shapes, ranging from spheres to Archean or earlier – Present rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Had'n Archean Proterozoic Pha. Bacteria inhabit soil, water, acidic hot springs, radioactive waste,[4] and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. 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,[5] forming a biomass which exceeds that of all plants and [6] animals. Bacteria are vital in recycling nutrients, with Scanning electron micrograph of many of the stages in nutrient cycles dependent on these Escherichia coli rods organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. In the biological communities Scientific classification surrounding hydrothermal vents and cold seeps, bacteria Domain: Bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and Woese, Kandler & Wheelis, methane, to energy. On 17 March 2013, researchers reported 1990[1] data that suggested bacterial life forms thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the Phyla[2] deepest part of the Earth's oceans.[7][8] Other researchers reported related studies that microbes thrive inside rocks up ◾ Gram positive / no outer to 580 metres below the sea floor under 2.6 kilometres of membrane ocean off the coast of the northwestern United States.[7][9] According to one of the researchers, "You can find microbes Actinobacteria (high-G+C) everywhere — they're extremely adaptable to conditions, Firmicutes (low-G+C) and survive wherever they are."[7] Tenericutes (no wall) Most bacteria have not been characterised, and only about ◾ Gram negative / outer half of the bacterial phyla have species that can be grown in membrane present the laboratory.[10] The study of bacteria is known as bacteriology, a branch of microbiology. Aquificae Bacteroidetes/Fibrobacteres–Chlorobi (FCB group) https://en.wikipedia.org/wiki/Bacteria 12/28/2016 Bacteria - Wikipedia Page 2 of 33 There are approximately ten times as many bacterial cells in Deinococcus-Thermus the human flora as there are human cells in the body, with Fusobacteria the largest number of the human flora being in the gut flora, Gemmatimonadetes and a large number on the skin.[11] The vast majority of the Nitrospirae bacteria in the body are rendered harmless by the protective Planctomycetes effects of the immune system, and some are beneficial. –Verrucomicrobia/Chlamydiae However, several species of bacteria are pathogenic and (PVC group) cause infectious diseases, including cholera, syphilis, Proteobacteria anthrax, leprosy, and bubonic plague. The most common Spirochaetes fatal bacterial diseases are respiratory infections, with Synergistetes tuberculosis alone killing about 2 million people per year, ◾ Unknown / ungrouped mostly in sub-Saharan Africa.[12] In developed countries, antibiotics are used to treat bacterial infections and are also Acidobacteria used in farming, making antibiotic resistance a growing Chloroflexi problem. In industry, bacteria are important in sewage Chrysiogenetes treatment and the breakdown of oil spills, the production of Cyanobacteria cheese and yogurt through fermentation, and the recovery of Deferribacteres gold, palladium, copper and other metals in the mining Dictyoglomi [13] sector, as well as in biotechnology, and the manufacture Thermodesulfobacteria of antibiotics and other chemicals.[14] Thermotogae Once regarded as plants constituting the class Synonyms Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells [3] do not contain a nucleus and rarely harbour membrane- Eubacteria Woese & Fox, 1977 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] Contents ◾ 1 Etymology ◾ 2 Origin and early evolution ◾ 3 Morphology ◾ 4 Cellular structure ◾ 4.1 Intracellular structures ◾ 4.2 Extracellular structures ◾ 4.3 Endospores ◾ 5 Metabolism ◾ 6 Growth and reproduction ◾ 7 Genomes ◾ 8Genetics https://en.wikipedia.org/wiki/Bacteria 12/28/2016 Bacteria - Wikipedia Page 3 of 33 ◾ 8.1 DNA transfer ◾ 8.2 Bacteriophages ◾ 9 Behaviour ◾ 9.1 Secretion ◾ 9.2 Bioluminescence ◾ 9.3 Multicellularity ◾ 9.4 Movement ◾ 10 Classification and identification ◾ 11 Interactions with other organisms ◾ 11.1 Predators ◾ 11.2 Mutualists ◾ 11.3 Pathogens ◾ 12 Significance in technology and industry ◾ 13 History of bacteriology ◾ 14 See also ◾ 15 References ◾ 16 Further reading ◾ 17 External links Etymology The word bacteria is the plural of the New Latin bacterium, which is the latinisation of Life timeline [15] the Greek βακτήριον (bakterion), the view • discuss • diminutive of βακτηρία (bakteria), meaning 0 — ←Earliest humans P Flowers "staff, cane",[16] because the first ones to be Mammals – h [17][18] a Dinosaurs discovered were rod-shaped. n Land life -500 — r ←Cambrian explosion z Origin and early evolution – c Multicellular The ancestors of modern bacteria were -1000 — life Earliest sexual unicellular microorganisms that were the – ← first forms of life to appear on Earth, about P reproduction 4 billion years ago. For about 3 billion -1500 — r o years, most organisms were microscopic, t and bacteria and archaea were the dominant – e r forms of life.[19][20] In 2008, fossils of -2000 — o Eukaryotes z macroorganisms were discovered and o named as the Francevillian biota. Although – i ←Oxygen Crisis c bacterial fossils exist, such as stromatolites, -2500 — ←Atmospheric oxygen their lack of distinctive morphology prevents them from being used to examine – A the history of bacterial evolution, or to date photosynthesis https://en.wikipedia.org/wiki/Bacteria 12/28/2016 Bacteria - Wikipedia Page 4 of 33 the time of origin of a particular bacterial -3000 — r – c species. However, gene sequences can be h used to reconstruct the bacterial phylogeny, e -3500 — ←Earliesta oxygen and these studies indicate that bacteria n diverged first from the archaeal/eukaryotic – lineage.[21] Bacteria were also involved in ←LHB meteorites -4000 — H the second great evolutionary divergence, a ←Earliest life that of the archaea and eukaryotes. Here, – d (-4100) e eukaryotes resulted from the entering of a ←Earliest water ancient bacteria into endosymbiotic -4500 — n ←Earliest Earth associations with the ancestors of Axis scale: millions of (-4540)years. eukaryotic cells, which were themselves Also see: Human timeline & Nature timeline possibly related to the Archaea.[22][23] This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya (sometimes in highly reduced form, e.g. in ancient "amitochondrial" protozoa). Later on, some eukaryotes that already contained mitochondria also engulfed cyanobacterial-like organisms. This led to the formation of chloroplasts in algae and plants. There are also some algae that originated from even later endosymbiotic events. Here, eukaryotes engulfed a eukaryotic algae that developed into a "second-generation" plastid. [24][25] This is known as secondary endosymbiosis. Morphology Bacteria display a wide diversity of shapes and sizes, called morphologies. Bacterial cells are about one-tenth the size of eukaryotic cells and are typically 0.5 –5.0 micrometres in length. However, a few species are visible to the unaided eye — for example, Thiomargarita namibiensis is up to half a millimetre long[26] and Epulopiscium fishelsoni reaches 0.7 mm.[27] Among the smallest bacteria are members of the genus Mycoplasma, which measure only 0.3 micrometres, as small as the largest viruses.[28] Some bacteria may be even smaller, but these ultramicrobacteria are not well-studied.[29] Most bacterial species are either spherical, Bacteria display many cell morphologies and arrangements called cocci (sing. coccus, from Greek kókkos, grain, seed), or rod-shaped, called bacilli (sing. bacillus, from Latin baculus, stick). Elongation is associated with swimming.[30] Some bacteria, called vibrio, are shaped like slightly curved rods or comma-shaped; others can be spiral- https://en.wikipedia.org/wiki/Bacteria 12/28/2016 Bacteria - Wikipedia Page 5 of 33 shaped, called spirilla, or tightly coiled, called spirochaetes. A small number of species even have tetrahedral or cuboidal shapes.[31] More recently, some bacteria were discovered deep under Earth's crust that grow as branching filamentous types with a star-shaped cross-section. The large surface area to volume ratio of this morphology may give these bacteria an advantage in nutrient-poor environments.[32] This wide variety of shapes is determined by the bacterial cell wall and cytoskeleton, and is important because it can influence the