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Topic: Rhizobia

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	Rhizobia - Wikipedia, the free encyclopedia
		Rhizobia (from the Greek words riza = root and bios = Life) are soil bacteria that fix nitrogen (diazotrophy) after becoming established inside root nodules of legumes (Fabaceae).
		Rhizobia are unique because they live in a symbiotic relationship with legumes.
		The legume–Rhizobia symbiosis is a classic example of mutualism — rhizobia supply ammonia or amino acids to the plant and in return receive organic acids (principally as the dicarboxylic acids malate and succinate) as a carbon and energy source — but its evolutionary persistence is actually somewhat surprising.
	en.wikipedia.org /wiki/Rhizobia (582 words)

	Legume Seed Inoculants
		The relationship between the legume and rhizobia is symbiotic, or mutually beneficial.
		Rhizobia species are identified by their ability to form nodules on specific legume species.
		Rhizobia cells are living bacteria that must be kept viable until planting.
	www.ext.colostate.edu /pubs/crops/00305.html (1309 words)

	CLIMA - Rhizobia
		Rhizobia inside root nodules convert nitrogen from the air into nitrogen fertiliser for the plant.
		The lupin plant on the left was planted with rhizobia and the plant on the right was planted without.
		Rhizobia are very small - it would take between 500 and 1,000 rhizobia to measure 1mm (check your ruler to see how small that is!).
	www.clima.uwa.edu.au /schools/beanfiles/episodes/episode5/rhizobia (226 words)

	EMD Crop BioScience
		Nitrogen-fixing bacteria known as Rhizobia are introduced into the soil either directly or by applying them to the seed.
		The symbiotic relationship occurs as the plant supplies the Rhizobia with photosynthate - a food source the bacteria uses for energy - and the bacteria convert nitrogen gas (N2) to ammonia nitrogen (NH3) for the host.
		The Rhizobia bacteria were isolated, and in 1890 two other German scientists, Nobbe and Hiltner, demonstrated the advantage of adding pure bacteria with the seed at planting.
	www.nitragin.com /misc/inoculation_guide.cfm (463 words)

	The Common Nodulation Genes of Astragalus sinicus Rhizobia Are Conserved despite Chromosomal Diversity -- Zhang et al. ...
		Rhizobia are soil bacteria that can form nodules, in which they fix nitrogen, on leguminous plants in a host-specific manner.
		rhizobia are diverse (17, 42): of 204 strains analyzed, all
		The glutamine synthetases of rhizobia: phylogenetic and evolutionary implications.
	aem.asm.org /cgi/content/full/66/7/2988 (4062 words)

	Rhizobium Research Laboratory - Home
		Inoculant-quality rhizobia: Strains of rhizobia which combine superior nodulation and nitrogen-fixing ability with the other traits needed in a strain suitable for use in inoculant preparations.
		Rhizobia: The common name for several genera of bacteria which have the ability to infect the root of legumes and to produce root nodules.
		With legumes and rhizobia, the legume gains by having the microbe supply it an additional source of nitrogen it can use for growth: the microbe gains a source of energy for growth and a habitat (the nodule) within which it is protected from outside stress.
	www.rhizobium.umn.edu /glossary.php (2292 words)

	RRL - FAQ
		Rhizobia is the common name given to a group of small, rod- shaped, Gram -ve bacteria, which collectively have the ability to produce nodules on the roots (or, in some cases, the stems) of leguminous plants.
		Thus, rhizobia isolated from one species of clover would usually nodulate other species of clover, and were then collectively called Rhizobium trifolii, while rhizobia isolated from medics would also nodulate lucerne and fenugreek, and were called R.meliloti.
		While inoculant rhizobia should all be capable of fixing nitrogen within the nodules produced by their host, few have been shown to exhibit this property when growing in pure culture.
	www.rhizobium.umn.edu /faq/whatrhizobia.php (446 words)

	The Overstory #65--Biological Nitrogen Fixation
		Rhizobia are able to convert the nitrogen gas in the atmosphere into amino acids, which are the building blocks of proteins.
		Rhizobia inoculants are live bacteria cultures that are applied to seeds or young plants, infecting their root systems with the beneficial bacteria.
		Using rhizobia inoculants ensures that the correct rhizobia bacteria associate with the plant, and also that the association forms early in the plant's life to accelerate its early growth and establishment.
	www.agroforestry.net /overstory/overstory65.html (1479 words)

	What are rhizobia? (Site not responding. Last check: 2007-10-31)
		Rhizobia consist of 55 species found in 12 genera [1].
		The legume–Rhizobia symbiosis is a classic example of mutualism — rhizobia supply ammonia or amino acids to the plant and in return receive organic acids (principally as the dicarboxylic acids malate and succinate) as a carbon and energy source — but its evolutionary persistence is actually somewhat surprising.
		Many other species of bacteria are able to fix nitrogen (diazotrophs), including Frankia which is symbiotic (but not in nodules), and and Azospirillum which is free-living.
	www.rhizobia.co.nz /rhizobia.html (524 words)

	Microbes on plants :: Microbiology and Bacteriology :: The world of microbes (Site not responding. Last check: 2007-10-31)
		These are the main molecular signal produced by the rhizobia that indicate to the plant that a suitable symbiotic microbe is nearby.
		In these cases, the secretion of nod factors by the rhizobia causes cortical cell division in the roots, causing swelling and the formation of cracks in the epidermis.
		The theory is that rhizobia were initially pathogens, and plants found a way to control the infection and turn it toward their own well-being.
	www.bact.wisc.edu /Microtextbook/index.php?name=Sections&req=viewarticle&artid=121&page=1 (1854 words)

	Engineering Competitive Soybean Rhizobia (Site not responding. Last check: 2007-10-31)
		The availability of rhizobia with nodulation abilities made more efficient as a result of the competitive advantage conferred by their ability to use mannityl opines will result in more efficient use of available nitrogen and hence more efficient soybean production.
		In the case of the nodulating rhizobia this requirement its inferred by the often seen inability of commercial inocula to efficiently nodulate a large proportion of the treated plants (S, 6).
		Once stable regenerants are available, the ability of the engineered rhizobia to interact with their engineered host can be tested and the competitive advantage of the system determined.
	www.ag.uiuc.edu /~stratsoy/ispob_db/lor_html/51.html (4474 words)

	Inoculation of Forage and Grain Legumes - Agronomy Facts 11
		Rhizobia bacteria are fairly specific as to which legumes they will infect, form nodules on the roots of, and for which they will fix nitrogen.
		The pelleted type of preinoculated seed is generally preferred on the basis of research that shows that bacteria live longer on the pelleted seed and that this type of preinoculated seed results in formation of a greater number of root nodules.
		Sugars or carbohydrates of a legume infected with Rhizobia are the energy and hydrogen source used by the bacteria to fix N from the air at high energy costs to the plant.
	cropsoil.psu.edu /extension/facts/agfacts11.cfm (2235 words)

	Symbiotic Nitrogen Fixation (Site not responding. Last check: 2007-10-31)
		Rhizobia can infect their hosts and induce root- or stem-nodule formation using several different mechanisms.
		In indeterminate nodules this includes formation of a nodule primordium, with rhizobia then released into modified cells of the root cortex, where again they are enclosed within a plant-derived peribacteroid membrane.
		The demonstration that the nodulation genes of many rhizobia are carried on plasmids led to more detailed molecular studies of infection.
	www.soils.agri.umn.edu /academics/classes/soil3612/Symbiotic_Nitrogen_Fixation/Inititation.htm (707 words)

	Protein Kinases role in Nodulation
		The nodules provide a microenvironment for the bacteria, in which symbiotic interactions occur involving transfer of carbon and energy sources from the plant to the bacteria; the rhizobia are nitrogen-fixing bacteria, converting atmospheric nitrogen into ammonium which serves as a nitrogen source for the plant.
		While wild type plants respond to the presence of rhizobia with branching and curling of root hairs, resulting in entrapment of a bacterial micro-colony in which an intracellular infection structure called the infection thread is formed (symrk mutants figure a); mutant roots failed to curl and did not form infection threads.
		Interestingly, it could be seen that the extent of root hair deformation was much higher in mutant plants than in wild type, indicating that wild type plants have mechanisms to negatively regulate root cell competence, and that this mechanism is disrupted in the mentioned mutants (Stracke et al, 2002).
	www.tau.ac.il /~ecology/virtau/3-amnon_koren/NODULAtion.htm (2707 words)

	Appendices
		The rhizobia to be used for inoculation may be isolated by the researcher himself from nodules, dried root material, or soil, or be requisitioned from a Rhizobium culture collection.
		Rhizobia are mobile organisms and are easily transferred accidentally by water movement, humans, or animals from treatment to treatment or plot to plot.
		Rhizobia carry on the fixation of atmospheric N in forms used as nutrients by the host legumes.
	www.fao.org /Wairdocs/ILRI/x5545E/x5545e0a.htm (3397 words)

	Agribiotics Inc. is a 100% Canadian owned company dedicated to producing quality biologicals for agriculture.
		"Rhizobia" is the general name for the group of bacteria that have a very special, very beneficial, relationship with certain specific plants -- the legumes.
		It is at this time that the rhizobia on that surface where it touches are transferred to the growing root tip.
		The rhizobia cannot move to assist in the process of adsorption by the radicle.
	www.agribiotics.com /background.html (1934 words)

	NOFA Massachusetts: June - July 2002 News: Planting Ideas: Rhizobia? What are They?
		Rhizobia are bacteria that form symbiotic relationships with legumes.
		When Rhizobia enter the root-hairs of a legume they stimulate the infected plant to produce enlargements on the roots called nodules.
		Rhizobia are somewhat specific in forming symbiotic relationships and not all species will produce nodulation and nitrogen fixation with any legume.
	www.nofamass.org /news/article.php?issue=5&article=40 (330 words)

	alpha-proteobacteria :: Microbiology and Bacteriology :: The world of microbes
		Rhizobia were originally identified as bacteria that form nodules on leguminous plants and were all lumped into one genus, Rhizobium.
		Rhizobia are gram-negative chemoheterotrophic organotrophs and are capable of growth on a large array of carbohydrates.
		There has been substantial scientific interest in the rhizobia since many of the plants they nodulate are important crops around the world and the rhizobia contribute significantly to the overall fertility of the soil.
	www.bact.wisc.edu /Microtextbook/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=101&page=1 (5412 words)

	Nitrogen Fixation
		Rhizobia are gram-negative bacilli that live freely in the soil (especially where legumes have been grown).
		Because of the specificity of the interaction between the Nod factor and the receptor on the legume, some strains of rhizobia will infect only peas, some only clover, some only alfalfa, etc. The treating of legume seeds with the proper strain of rhizobia is a routine agricultural practice.
		Assuming that the ancestors of the rhizobia could carry out the entire process by themselves — as many other soil bacteria still do — they must have gained some real advantage from evolving to share the duties with the legume.
	home.comcast.net /~john.kimball1/BiologyPages/N/NitrogenFixation.html (845 words)

	CHARACTERIZATION OF RHIZOBIA FROM LEUCAENA
		Seventy-six rhizobia were isolated from the nodules of Leucaena plants of various genotypes growing in a wide range of soil types and climatic regions.
		Eight distinct somatic serogroups of Leucaena rhizobia were identified by using strain-specific fluorescent antibodies.
		The immunofluorescence cross-reactions of Leucaena rhizobia serogroups among themselves and with other species of fast- and slow-growing rhizobia were very low.
	www.egeinfonet.i8.com /pub/1992/3.html (138 words)

	ARS \| Publication request: Characteristics of Rhizobia Associated with Dalea Spp. in Three Prairie Areas of Minnesota.
		From the results we concluded that the rhizobia of this legume are highly diverse and vary according to prairie of origin.
		In this paper we consider the diversity of the rhizobia associated with the indigenous legume Dalea purpurea in three fragmented prairie areas in Minnesota.
		This variation in the dominant microsymbiont species across the three prairies studied was unexpected, but could have been influenced by both the limited number of samples we were allowed to take from each area, and by unanticipated cross nodulation between native legumes in each prairie area.
	www.ars.usda.gov /research/publications/Publications.htm?seq_no_115=164557&pf=1 (396 words)

	Environmental Expert.com. Release of transgenic bacterial inoculants - rhizobia as a case study
		Rhizobia, the bacteria that form N2-fixing symbioses with leguminous plants, have a long history of safe use as seed inoculants, their biology is relatively well known, and they represent a relevant model system.
		The monitoring of survival and spread of rhizobia was greatly improved by the presence of novel marker genes.
		Tagging of rhizobia with marker genes provided more accurate information compared to the use of conventional strains, illustrating an important application of genetic modification, for tracking bacteria in the environment.
	www.environmental-expert.com /resulteacharticle4.asp?cid=6063&codi=5313 (277 words)

	Phenotypic and Genetic Diversity of Rhizobia Isolated from Nodules of Clover Grown in a Zinc and Cadmium Contaminated ...
		Phenotypic and Genetic Diversity of Rhizobia Isolated from Nodules of Clover Grown in a Zinc and Cadmium Contaminated Soil -- Delorme et al.
		Phenotypic and Genetic Diversity of Rhizobia Isolated from Nodules of Clover Grown in a Zinc and Cadmium Contaminated Soil
		Effect of Zn on the growth of rhizobia isolated from nodules present on indigenous clover growing in both low and high metal soil, or from nodules of the plants used to determine the most probable number (MPN) of rhizobia in the high metal soil.
	soil.scijournals.org /cgi/content/full/67/6/1746 (4997 words)

	ALFALFA RHIZOBIA IN SOUTHERN ONTARIOSOILS
		These rhizobia were absent in soil samples from only one of 37 farms.
		Populations of rhizobia were low in soils which were both acidic and had a high sand content.
		These rhizobia are able to fix up to 300 kg/ha of atmospheric nitrogen (N2) and supply all the N required by the crop.
	www.plant.uoguelph.ca /performance_recommendations/ofcc/pub/rhizobia.htm (853 words)

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