nitrogen-fixing bacteria

nitrogen-fixing bacteria

▪ biology and ecology
      microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen, inorganic compounds usable by plants. More than 90 percent of all nitrogen fixation is effected by them.

      Two kinds of nitrogen fixers are recognized: free-living (non-symbiotic) bacteria, including the cyanobacteria (or blue-green algae) Anabaena and Nostoc and such genera as Azotobacter, Beijerinckia, and Clostridium; and mutualistic (symbiotic) bacteria such as Rhizobium, associated with leguminous plants, and Spirillum lipoferum, associated with cereal grasses.

      The symbiotic nitrogen-fixing bacteria invade the root hairs of host plants, where they multiply and stimulate formation of root nodules, enlargements of plant cells and bacteria in intimate association. Within the nodules the bacteria convert free nitrogen to nitrates, which the host plant utilizes for its development. To insure sufficient nodule formation and optimum growth of legumes (e.g., alfalfa, beans, clovers, peas, soybeans), seeds are usually inoculated with commercial cultures of appropriate Rhizobium species, especially in soils poor or lacking in the required bacterium. See also nitrogen cycle.

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Universalium. 2010.

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  • nitrogen-fixing — adj capable of nitrogen fixation <nitrogen fixing bacteria> * * * ni·tro·gen fix·ing (niґtro jən fikґsing) accomplishing nitrogen fixation (see under fixation); said of certain bacteria …   Medical dictionary

  • nitrogen-fixing — adjective contributing to the process of nitrogen fixation • Pertains to noun: ↑nitrogen fixation * * * | ̷ ̷ ̷ ̷ ̷ ̷| ̷ ̷ ̷ ̷ adjective Etymology: nitrogen + fixing, from present participle of fix (I) : having the power of nitrogen fixation… …   Useful english dictionary

  • nitrogen-fixing — adjective Date: 1899 capable of nitrogen fixation < nitrogen fixing bacteria > …   New Collegiate Dictionary

  • Nitrogen — carbon ← nitrogen → oxygen ↑ N ↓ P …   Wikipedia

  • nitrogen fixation — 1. any process of combining atmospheric nitrogen with other elements, either by chemical means or by bacterial action: used chiefly in the preparation of fertilizers, industrial products, etc. 2. this process as performed by certain bacteria… …   Universalium

  • Nitrogen cycle — Schematic representation of the flow of nitrogen through the environment. The importance of bacteria in the cycle is immediately recognized as being a key element in the cycle, providing different forms of nitrogen compounds assimilable by higher …   Wikipedia

  • bacteria — bacterial, adj. bacterially, adv. /bak tear ee euh/, n.pl., sing. bacterium / tear ee euhm/. ubiquitous one celled organisms, spherical, spiral, or rod shaped and appearing singly or in chains, comprising the Schizomycota, a phylum of the kingdom …   Universalium

  • nitrogen cycle — /ˈnaɪtrədʒən saɪkəl/ (say nuytruhjuhn suykuhl) noun the continuous circulation of nitrogen and nitrogen compounds in nature between the atmosphere, the soil, and the various organisms to which nitrogen is essential. The nitrogen cycle describes… …  

  • nitrogen fixation — The metabolic process in which atmospheric molecular nitrogen is reduced to ammonia; carried out by cyanobacteria, Rhizobium, and other nitrogen fixing bacteria …   Dictionary of microbiology

  • Nitrogen fixation — is the natural process, either biological or abiotic, by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3).[1] This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of …   Wikipedia

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