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Trophic mutualism is a key type of ecological mutualism. Specifically, "trophic mutualism" refers to the transfer of energy and nutrients between two species. This is also sometimes known as resource-to-resource mutualism. Trophic mutualism often occurs between an autotroph and a heterotroph.〔Odum, Eugene. Fundamentals of Ecology. 3rd ed. Philadelphia: W.B. Saunders Company, 1971. 〕 Although there are many examples of trophic mutualisms, the heterotroph is generally a fungus or bacteria. This mutualism can be both obligate and opportunistic. ==Examples == *Rhizobia- Rhizobia are bacteria that conduct Nitrogen fixation for legume plants. Specifically, these bacteria can be from generas ''Allorhizobium, Azorhizobium, Bradyrhizobium, Mesorhizobium, Rhizobium, or Sinorhizobium''.〔Vessey, K.J., K. Pawlowski, and B. Bergman, Root-based N2-fixing symbioses: Legumes, actinorhizal plants, Parasponiasp. and cycads. Plant and Soil 2005. 266(1-2): p. 205-230.〕 In this mutualistic relationship, the bacteria grow on or within the root hair and penetrate into the plant tissues〔Townsend, C.R., M. Begon, and J.L. Harper, Essentials Of Ecology Third Edition 2008, Malden, MA: Backwell Publishing〕 Although the exact means of interaction between the Rhizobia and plant varies with genus and species, all forms of this interaction are made up of the infection of bacteria, bacteria colonization, control of O2, and exchange of Carbon and Nitrogen.〔Vessey, K.J., K. Pawlowski, and B. Bergman, Root-based N2-fixing symbioses: Legumes, actinorhizal plants, Parasponiasp. and cycads. Plant and Soil 2005. 266(1-2): p. 205-230.〕 The role that rhizobias play in fixing nitrogen for legumes is the basis for why legumes can be used in crop rotation.〔Saito, K., B. Linquist, and B. Keobualapha, Stylosanthes guianensis as a short-term fallow crop for improving upland rice productivity in northern Laos. Field Crops Research 2006. 96(2/3): p. 438-447.〕 *Mycorrhizae- Mycorrhizae are similar to rhizobia in that they interact with plants at their roots. Whereas Rhizobia are bacteria that fix nitrogen, mycorrhizas are fungi that bring nutrients to the plants in return for carbon. Mycorrhizas are also capable of improving water uptake and communicating to their hosts to resist to pathogens.〔Douglas H. Boucher, Sam James and Kathleen H. Keeler Annual Review of Ecology and Systematics, Vol. 13, (1982), pp. 315-347〕 Three main types of mycorrhizae exist: :# Arbuscula: found in non-woody and tropical plants :# Ectomycorrhiza: found in boreal and temperate forests :# Ericoid: found in species of the heathland.〔Townsend, C.R., M. Begon, and J.L. Harper, Essentials Of Ecology Third Edition 2008, Malden, MA: Backwell Publishing〕 *Digestive symbyotes – Digestive symbyotes are an example of an important trophic mutualism that does not occur between an autotroph and heterotroph. Bacteria known as “extracellular symbionts”〔Townsend, C.R., M. Begon, and J.L. Harper, Essentials Of Ecology Third Edition 2008, Malden, MA: Backwell Publishing〕 live within the gastrointestinal tracts of vertebrates, where they aid in the digestion of food. The bacteria benefits by extracting substrates from the eaten food, while the animal’s assimilation is increased by being able to digest certain foods that it’s natural system cannot. (book) In addition, these bacteria create short-chain fatty acids (SCFA), providing the vertebrate with energy totaling up to anywhere from 29%-79% of the vertebrate’s maintenance energy depending on the species.〔Stevens, C.E. and I.D. Hume, Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients. Physiological Reviews, 1998. 72(2): p. 383-427.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Trophic mutualism」の詳細全文を読む スポンサード リンク
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