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Topic: Nitrogen fixation

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Nitrogen cycle

Heterocyst

Nitrogen

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	PNAS Editor Details
		The first is a comprehensive system for analysis of the chromosome of the photosynthetic bacterium, Rhodobacter capsulatus, which can do both photosynthesis and nitrogen fixation and can also grow on a wide variety of carbon sources.
		The second is the study of the differentiation of cells specialized for nitrogen fixation in the cyanobacterium Anabaena, which grows in filaments of several hundred cells.
		These cells are anaerobic factories for nitrogen fixation, trading amino acids for carbohydrates with their vegetative cell neighbors.
	nrc88.nas.edu /pnas_search/memberDetails.aspx?ctID=14176 (0 words)

	The Environmental Literacy Council - Nitrogen
		Nitrogen was discovered in 1772 by Scottish chemist Daniel Rutherford when he removed oxygen and carbon dioxide from air and showed that the residual gas would not support fires or living organisms.
		Nitrogen is the sixteenth most abundant element in seawater and a negligible amount appears in the igneous rock of the Earth's crust.
		Liquid nitrogen is used to keep foods and biological specimens frozen, and gaseous nitrogen is used in environments where a non-reactive gas is needed to shield something from oxidization.
	www.enviroliteracy.org /article.php/1007.html (1155 words)

	Nitrogen Fixation (Site not responding. Last check: )
		Nitrogen is a primary nutrient for all green plants, but it must be modified before it can be readily utilized by most living systems.
		Nitrogen fixation is one process by which molecular nitrogen is reduced to form ammonia.
		The nitrogen that is fixed by the processes described above is eventually returned to the atmosphere by this denitrification process, to complete what is commonly referred to as the "nitrogen cycle".
	library.kcc.hawaii.edu /external/chemistry/everyday_nitrogen.html (359 words)

	NITROGEN FIXATION,
		nitrogen is converted into a chemical compound that is essential for plant growth and is also used in industrial chemical production.
		Much smaller amounts of nitrogen are fixed in the soil by nonsymbiotic (free-living) bacteria such as the aerobes, which function in the presence of oxygen, and bacteria of the genera Klebsiella and Bacillus, which function without oxygen.
		Some forms of blue-green bacteria also fix nitrogen, such as the genus Anabaena, which, in symbiosis with the water fern Azolla pinnata, is said to markedly increase rice yields, as was the case in paddies in the Thai Binh region of northern Vietnam.
	www.history.com /encyclopedia.do?vendorId=FWNE.fw..ni050100.a#FWNE.fw..ni050100.a (460 words)

	The Nitrogen Cycle
		Nitrogen is an incredibly versatile element, existing in both inorganic and organic forms as well as many different oxidation states.
		The movement of nitrogen between the atmosphere, biosphere, and geosphere in different forms is described by the nitrogen cycle (Figure 1), one of the major biogeochemical cycles.
		The ammonia produced by nitrogen fixing bacteria is usually quickly incorporated into protein and other organic nitrogen compounds, either by a host plant, the bacteria itself, or another soil organism.
	www.visionlearning.com /library/module_viewer.php?mid=98 (1774 words)

	The Environmental Literacy Council - Nitrogen Cycle
		Nitrogen is both the most abundant element in the atmosphere and, as a building block of proteins and nucleic acids such as DNA, a crucially important component of all biological life.
		Once in the soils and surface waters, nitrogen undergoes a set of changes: its two nitrogen atoms separate and combine with hydrogen to form ammonia (NH This is done by microorganisms that fall into three broad categories: bacteria living in symbiotic relationships with certain plants, free anaerobic bacteria, and algae.
		Nitrogen compounds in various forms, such as nitrate, nitrite, ammonia, and ammonium are taken up from soils by plants which are then used in the formation of plant and animal proteins.
	www.enviroliteracy.org /article.php/479.php (739 words)

	Botany online: Interactions of Plants and Bacteria — Nitrogen Fixation
		Nitrogen fixation has been thoroughly covered during the last years, since genetic engineering fosters the hope for techniques improving the nitrogen supply of plants.
		Although extremely important, the contribution of symbiotic bacteria to the nitrogen supply of plants is very small when seen in relation to nature’s total nitrogen budget.
		Nitrogen fixation takes place in specialized cells, the heterocysts, that alternate with vegetative, photosynthetically active cells in the alga’s filaments.
	www.biologie.uni-hamburg.de /b-online/e34/34b.htm (1839 words)

	Nitrogen Metabolism and the Urea Cycle
		Nitrogen fixation is carried out by bacterial nitrogenases forming reduced nitrogen, NH which can then be used by all organisms to form amino acids.
		Nitrogen, nitrites and nitrates are acted upon by bacteria (nitrogen fixation) and plants and we assimilate these compounds as protein in our diets.
		This class of reactions funnels nitrogen from all free amino acids into a small number of compounds; then, either they are oxidatively deaminated, producing ammonia, or their amine groups are converted to urea by the urea cycle.
	www.indstate.edu /thcme/mwking/nitrogen-metabolism.html (4375 words)

	The Future is Abundant
		In addition, nitrogen compounds are concentrated when consumed by fish, birds and animals, all of whom secrete this concentrated nitrogen in their manure.
		In spite of all the nitrogen in the atmosphere, and all the ways in which nitrogen can be fixed into compounds usable to plants, it is still difficult to provide plants with the nitrogen they need.
		Although the basic nitrogen fixation process is the same with these plants as with legumes, most of their nitrogen contribution is in the form of falling leaves and decaying litter.
	www.tilthproducers.org /tfia/nitrogen.htm (1334 words)

	Crop productivity from biological nitrogen -DAWN - Business; February 20, 2006
		Inputs of nitrogen into agricultural systems are primarily from chemical fertilizers and nitrogen derived from atmospheric dinitrogen by the process of biological nitrogen fixation, which is the microbial conversion of atmospheric dinitrogen gas into plant usable ammonia.
		The precise quantities of nitrogen supplied to the biosphere by all the various processes is not accurately known, but it is generally agreed that the biological fixation of nitrogen gas is of major importance accounting for some hundred million tons of nitrogen fixed per year.
		Recent approaches to improving biological nitrogen fixation by soybean crops include attempts to optimize the numbers the members and effectiveness of rhizobia in the rooting zone, selection of elite strains of bradyzhizobia, improved maculation technique, and improvement in breeding programme for nitrate tolerance in soybean.
	www.dawn.com /2006/02/20/ebr6.htm (1525 words)

	Biological Nitrogen Fixation
		Nitrogen fixation rates from 75 to 300 kilograms of N per hectare per year (70 to 275 pounds of N per acre per year) are common in various combinations.
		Nitrogen fixation is characteristically higher in environments such as tropical soils, where such factors as substrate availability, temperature and moisture are more favorable to the maintenance and activity of a high bacterial population.
		Most of the nitrogen fixation in marine environments (about 20% of the total amount of annual biological fixation) is attributed to the cyanobacteria but many other kinds of nitrogen-fixing microorganisms have also been found in such environments.
	edis.ifas.ufl.edu /SS180 (2181 words)

	Nitrogen in the air feeds the oceans
		Nitrogen is a building block of life and an essential nutrient for phytoplankton and other aquatic life.
		The term "fixation" describes the process by which dinitrogen, an inert gas, is transformed into usable chemical forms such as nitrate, a compound of nitrogen and oxygen.
		The new study's estimate of global N2 fixation is large enough to account for the uptake by photosynthesis of the 1.5 billion metric tons of carbon dioxide thought to enter the ocean each year.
	www.eurekalert.org /pub_releases/2005-08/uosc-nit081005.php (792 words)

	Nitrogen Fertilizer for Alfalfa Production
		Nitrogen fertilizer is generally not required for alfalfa production since alfalfa can obtain its own nitrogen from the air.
		Nitrogen fixation is the process of obtaining nitrogen from the aire.
		Nevertheless, the possible negative effect of high temperatures on nitrogen fixation has been suggested as a cause for decreased yields during the summer.
	ag.arizona.edu /PLS/faculty/ottman/files/N_fert_alfalfa.htm (1309 words)

	Microbe fixes nitrogen at a blistering 92 C, evolution of nitrogen fixation \| Huliq: Breaking News
		A heat-loving archaeon capable of fixing nitrogen at a surprisingly hot 92 degrees Celsius, or 198 Fahrenheit, may represent Earth's earliest lineages of organisms capable of nitrogen fixation, perhaps even preceding the kinds of bacteria today's plants and animals rely on to fix nitrogen.
		Nitrogen can be fixed into ammonia, nitrate and other products that can be used by land and sea plants, which in turn are eaten by higher animals.
		Scientists have speculated since 1981 that nitrogen fixation was occurring at hydrothermal vents because vent animals had completely different nitrogen isotope ratios than non-vent deep sea animals.
	www.huliq.com /3054/microbe-fixes-nitrogen-at-a-blistering-92-c-evolution-of-nitrogen-fixation (538 words)

	WQ261 Nitrogen Fixation, MU Extension
		One of the most interesting forms of biological nitrogen fixation is that which takes place by microorganisms living in very small nodules on the roots of certain plants such as legumes.
		Of the total nitrogen required by legumes, generally about half is nitrogen fixed from the atmosphere, with the remainder being taken up from residual nitrate in the soil.
		This is because the ammonium (NH) produced from fixation is readily used by the legume plant for growth and development, and is not further converted to nitrate (NO Although nitrogen exists in many forms in the soil, it is the nitrate form that primarily affects water quality.
	muextension.missouri.edu /explore/envqual/wq0261.htm (807 words)

	Nitrogen Cycle
		Nitrogen will only react with oxygen in the presence of high temperatures and pressures found near lightning bolts and in combustion reactions in power plants or internal combustion engines.
		Nitrogen in the air becomes a part of biological matter mostly through the actions of bacteria and algae in a process known as nitrogen fixation.
		Nitrogen and hydrogen are reacted under great pressure and temperature in the presence of a catalyst to make ammonia.
	www.elmhurst.edu /~chm/vchembook/307nitrogen.html (277 words)

	Nitrogen Cycle
		About 78 percent of the atmosphere is made up of "free" nitrogen, or nitrogen that is not combined with other elements.
		Certain kinds of bacteria are able to use the free nitrogen in the air to make nitrogen compounds through a process known as nitrogen fixation.
		Most of the nitrogen fixation on Earth occurs as a result of the activity of bacteria.
	www.tnmanning.com /Test/Tests/nitrogen_cycle.htm (570 words)

	Zehr Research
		Nitrogen fixation is the conversion of gaseous dinitrogen to ammonium.
		In the case of nitrogen, nitrogen sources are primarily the flux of nitrate from nutrient-rich deep water across the nutricline and thermocline, and the recycling of nitrogen from excretion of waste my microzooplankton, zooplankton and larger animals.
		Despite the fact that reduced nitrogen is found in low concentrations in the open ocean, measured rates of nitrogen fixation are low, and only a few nitrogen fixing organisms have been identified.
	ic.ucsc.edu /~zehrj/ocea80a/zehrresearch2.html (411 words)

	Symbiotic Nitrogen Fixation (Site not responding. Last check: )
		Estimates of the contribution of these different symbioses to the global nitrogen economy vary, but crop and pasture legumes alone are grown on more than 250 million ha.
		The direct availability of the fixed N to the host allows it to grow in environments that are low in N, and at the same time to cut losses from denitrification, volatilization and leaching, improving the sustainability of both agricultural and natural systems that involve such symbioses.
		The contrast is evident in data presented by Van Kessel and Hartley (2000) and Andrade and Hungria (2001).
	www.soils.agri.umn.edu /academics/classes/soil3612/Symbiotic_Nitrogen_Fixation/Introduction.htm (405 words)

	Nitrogen fixation Summary
		Although it was already known that plants absorb nitrogen compounds from the soil through their roots, most people thought that these compounds had to be restored to the soil by the addition of organic or chemical fertilizers.
		To utilize nitrogen, organisms require that it be fixed (combined) in the form of ammonium (NH) or nitrate ions (NO The bacteria that accomplish nitrogen fixation are either free-living or form symbiotic associations with plants or other organisms such as termites or protozoa.
		Nitrogen fixation is performed naturally by a number of different prokaryotes, including bacteria, and actinobacteria certain types of anaerobic bacteria.
	www.bookrags.com /Nitrogen_fixation (2852 words)

	Geotimes - March 2007 - Nitrogen cycle in oceans surprises researchers
		To get a better sense of where most nitrogen fixation was occurring, Deutsch and his colleagues decided that rather than considering where the nitrogen-fixing bacteria might prefer to live, they would look instead for evidence of their activity — specifically, the ratio of nitrogen to phosphorus in the waters.
		A link between denitrification and nitrogen fixation “makes eminent sense,” and suggests that the ocean nitrogen cycle may be in balance after all, if much more nitrogen fixation is occurring in large parts of the Pacific than had been thought, says Douglas Capone, a biological oceanographer at the University of Southern California.
		The discovery is just one of several that have shaken up the nitrogen world in recent years, including the discovery of an abundance of ancient nitrogen-fixing organisms called Archaea in oceans, and the discovery of a brand-new biological pathway for nitrogen removal, he says.
	www.geotimes.org /current/article.html?id=nn_nitrogen.html (743 words)

	Nitrogen Fixation
		Nitrogen fixation is conducted by a variety of bacteria, both as free-living organisms and in symbiotic association with plants.
		Because it is the principal source of the nitrogen in the soil, nitrogen that plants need to grow, nitrogen fixation is one of the most important biochemical processes on Earth.
		Soils deficient in molybdenum cannot sustain effective nitrogen fixation, and monitoring soil for this element is important to ensure maximum fixation in managed fields or pastures.
	www.biologyreference.com /Mo-Nu/Nitrogen-Fixation.html (579 words)

	LEGUME NITROGEN FIXATION AND TRANSFER (Site not responding. Last check: )
		Factors that influence the quantity of nitrogen fixed are the level of soil nitrogen, the rhizobia strain infecting the legume, amount of legume plant growth, how the legume is managed, and length of growing season.
		The primary pathways for nitrogen transfer from the legume to the soil are through grazing livestock and decomposition of dead legume plant material.
		This is a major nitrogen transfer pathway for cool-season annual legumes overseeded on warm-season perennial grasses because the clover-growing period occurs before the warm-season grass-growing period.
	overton.tamu.edu /clover/cool/nfix.htm (1520 words)

	Michael Swanwick's Periodic Table of Science Fiction
		Nitrogen is a colorless, odorless, tasteless gaseous element.
		Nitrogen fixation is the process of extracting free nitrogen from the air by combining it with other elements, either by chemical means or by bacterial action.
		Bacterial agents, called nitrogen fixers, are found in the nodules of leguminous plants, such as alfalfa, peas, and soybeans.
	www.scifi.com /scifiction/elements/nitrogen.html (180 words)

	Nitrogen Fixation by Legumes
		Within these nodules, nitrogen fixation is done by the bacteria, and the NH produced is absorbed by the plant.
		However, nitrogen fixation by legumes can be in the range of 25-75 pounds of nitrogen per acre per year in a natural ecosystem, and several hundred pounds in a cropping system.
		Nitrogen fertilizer is applied at planting to these legumes when grown on sandy or low organic matter soils to supply nitrogen to the plant before nitrogen fixation starts.
	www.csun.edu /~hcbio027/biotechnology/lec10/lindemann.html (1628 words)

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