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Topic: Diazotroph

In the News (Mon 6 Jul 09)

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	Diazotroph at AllExperts
		Diazotrophs are bacteria that fix atmospheric nitrogen gas into a more usable form such as ammonia (Postgate, 1998).
		A diazotroph is an organism that is able to grow without external sources of fixed nitrogen.
		Diazotrophs are scattered across bacterial taxonomic groups (mostly in the Eubacteria but also a couple of Archaea).
	en.allexperts.com /e/d/di/diazotroph.htm (712 words)

	North Inlet Microbial Observatory - Research
		There are specific types of microorganisms that are capable of carrying out different types of transformations, such as the oxidation of nitrogen compounds to nitrate or nitrite, the reduction of oxidized nitrogen compounds to ammonium, or the “fixation” of nitrogen from the atmosphere into ammonium.
		Yet we do know that the diazotrophic bacteria in these environments are extraordinarily diverse, and salt marsh diazotrophs include a large number of species that are apparently new to science.
		Diazotroph species diversity is assessed on the basis of differences in the sequences of the nifH genes found in those species.
	129.252.139.104:8088 /Research.html (1093 words)

	Rick Lovell's Lab
		Diazotroph strains demonstrated physiological adaptation to their high or low marsh origins, and more specifically to the host plant from which they were isolated.
		The relative abundances of select diazotrophs and diazotrophic activity were found to be persistent and resilient despite significant changes in abiotic and biotic environmental conditions.
		Physiological diversity of rhizoplane diazotrophs of the saltmeadow cordgrass, Spartina patens.
	www.biol.sc.edu /~lovell (5564 words)

	Pirana Project (Site not responding. Last check: 2007-09-16)
		This is a complex and understudied ecosystem that has significant impacts on marine resources in the region as well as in downstream areas such as the Caribbean Sea.
		Diazotrophs in turn have a major impact on other phytoplankton and trophic levels through input of fixed nitrogen (N).
		Diazotrophs may be affected by land use practices in the Amazon Basin and the African Sahel, and N2 fixed by marine plankton can affect humans by stimulating primary productivity and fishery yields.
	wrigley.usc.edu /bc/pirana.htm (422 words)

	Molecular Analysis of Diazotroph Diversity in the Rhizosphere of the Smooth Cordgrass, Spartina alterniflora -- Lovell ...
		The micro- and macrodiversity of diazotrophs occurring in the Spartina rhizosphere and the dissimilarity of assemblages from
		Microdiversity of culturable diazotrophs from the rhizoplanes of the salt marsh grasses Spartina alterniflora and Juncus roemerianus.
		Spatial and temporal assessment of diazotroph assemblage composition in vegetated salt marsh sediments using denaturing gradient gel electrophoresis analysis.
	aem.asm.org /cgi/content/full/66/9/3814 (5752 words)

	Glutamate synthase genes of the diazotroph Azospirillum brasilense. Cloning, sequencing, and analysis of functional ...
		Glutamate synthase genes of the diazotroph Azospirillum brasilense.
		A 10-kilobase EcoRI fragment of Azospirillum brasilense genomic DNA was cloned in Escherichia coli.
		Binding domains for flavin cofactors and NADPH, a domain for glutamine binding and activation, and cysteine clusters for iron-sulfur centers formation were tentatively identified on the basis of sequence comparison with flavoproteins, pyridine nucleotide-dependent enzymes, amidotransferases, and iron-sulfur proteins.
	www.ihop-net.org /UniPub/iHOP/gp/82275.html (167 words)

	Proceedings of International Symposium 2004
		Positive responses of the stem-pieces to ARA were detected, confirming the occurrence of diazotrophic endophytes in the stems of Japanese sweetpotato cultivars.
		Endophytic diazotrophs are habitating sweetpotato stems, and sweetpotato plants have a specific characteristic in nitrogen nutrition.
		Hence, further studies are required to elucidate the biological N2-fixing ability in sweetpotato plants by using several methodologies in pots and the field, and to clarify the colonization mechanism of the bacteria in sweetpotato plants.
	konarc.naro.affrc.go.jp /photo/symp2004/repo/contents/o8.html (1468 words)

	Azospirillum sp., diazotroph predominant in the cultivation of rice (Oryza sativa L.) in the province of Pinar de Rio (Site not responding. Last check: 2007-09-16)
		Azospirillum sp., diazotroph predominant in the cultivation of rice (Oryza sativa L.) in the province of Pinar de Rio
		Several diazotrophs were isolated and estimated by means of nitrogen-lacking selective media, using the quantitative serial dilution technique.
		The results showed that diazotrophs predominate inside the complete bacterial microbiota of this crop rhizosphere and rhizoplane.
	trophort.com /003/367/003367309.html (141 words)

	IngentaConnect Flooding and its influence on diazotroph populations and soil nit...
		IngentaConnect Flooding and its influence on diazotroph populations and soil nit...
		Effects of flooding on soil nitrogen (N), and asymbiotic nitrogen fixing bacterial (diazotroph) populations of the Okavango Delta were investigated.
		Diazotrophs from the rhizosphere of dominant annual and perennial grasses of the Okavango Delta were isolated on N-free composite media and identified applying morphological and biochemical criteria and Restriction Fragment Length Polymorphism (RFLP).
	www.ingentaconnect.com /content/nisc/sajb/2004/00000070/00000005/art00009 (334 words)

	Mycorrhiza Literature Exchange
		More ambiguous seems to be the habitat of the less well-known diazotroph Herbaspirillum seropedicae which originally was isolated from roots and stems of several cereals.
		Very recent results indicate that this diazotroph is closely related to sugar cane pathogens known as Pseudomonas rubrisubalbicans, a group of taxonomically misplaced Pseudomonas spp.
		Another new diazotroph, A. diazotrophicus, is also considered a plant endophyte in sugar cane stems and leaves.
	mycorrhiza.ag.utk.edu /latest/1992/92_dober1.htm (284 words)

	FAO/AGL - Soil Biodiversity Portal (Site not responding. Last check: 2007-09-16)
		Biological nitrogen fixation by obligate endophytic diazotroph bacteria (e.g.
		In addition, recent discoveries indicate that obligate endophytic diazotroph bacteria add as much as 150 kg/ha/year of nitrogen to agricultural and natural ecosystems (Dobereiner, 1995).
		Therefore biological nitrogen fixation is the major alternative to the use of commercial nitrogen fertilizer in agriculture (Dobereiner and Pedrosa, 1987).
	www.fao.org /ag/AGL/agll/soilbiod/consetxt.stm (2424 words)

	Jonathan P. Zehr
		Insights into diazotroph ecology in the Sargasso Sea and in meso- to bathypelagic waters of the North Atlantic and Pacific Oceans.
		Fingerprinting diazotroph communities in the Chesapeake Bay by using a DNA macroarray.
		Diazotroph Abundance and Diversity During a Large Bloom in the Oligotrophic North Pacific Gyre.
	oceansci.ucsc.edu /faculty/zehr.html (2545 words)

	Diazotrophs
		Yet we do know that the diazotrophic Bacteria in these environments are extraordinarily diverse, and salt marsh diazotrophs include a large number of species that are apparently new to science.
		The NIMO project examines the diversity of diazotrophs in a relatively pristine salt marsh ecosystem, the North Inlet salt marsh near Georgetown, SC.
		The goals of this project are to determine the diversity and activity of diazotrophic bacteria, examine the distributions of various diazotroph species, elucidate the environmental parameters that control diazotroph distribution and activity, and to formally describe diazotroph species previously unknown.
	serc.carleton.edu /microbelife/microbservatories/northinlet/diaz.html (477 words)

	Physiological Diversity of the Rhizosphere Diazotroph Assemblages of Selected Salt Marsh Grasses -- Bagwell et al. 64 ...
		Rhizosphere diazotroph assemblages of salt marsh grasses are thought to be influenced by host plant species and by a number
		Known diazotrophs are as follows: [1] Vibrio diazotrophicus, [2] Azospirillum brasilense, [3] Azotobacter chroococcum, [4] Klebsiella pneumoniae, [5] Azospirillum lipoferum, [6] Azotobacter diazotrophicus, [7] Rhizobium meliloti, [8] Rhizobium leguminosarum, and [9] Azotobacter vinlandii.
		diversity of diazotrophs in the rhizospheres of salt marsh grasses.
	aem.asm.org /cgi/content/full/64/11/4276 (4168 words)

	[No title]
		Rhizosphere diazotroph assemblages of salt marsh grasses are thought to be influenced by host plant species and by a number of porewater geochemical parameters.
		The diversity and key physiological features of culturable, O2-tolerant rhizosphere diazotrophs associated with the tall and short growth forms of Spartina alterniflora and with Juncus roemerianus were examined.
		A total of 339gram-negative strains were isolated by a root stab culture approach and morphologically and physiologically characterized by using API and BIOLOG tests.
	www.lycos.com /info/assemblages--species.html (688 words)

	Molecular Microbial Ecology
		I investigated the impacts of tidal gradients (creek-side to upper marsh) and carbon input (through root exudation) on diazotroph assemblage composition using denaturing gradient gel electrophoresis (DGGE) analysis.
		Spatial and temporal assessment of diazotroph assemblage composition in vegetated salt marsh sediments using denaturing gradient gel electrophoresis (DGGE) analysis.
		Physiological diversity of the rhizosphere diazotroph assemblages of selected salt marsh grasses.
	www-esd.lbl.gov /ECO/MME/staff_piceno.htm (441 words)

	Physiological Diversity of the Rhizosphere Diazotroph Assemblages of Selected Salt Marsh Grasses -- Bagwell et al. 64 ...
		Rhizosphere diazotroph assemblages of salt marsh grasses are thought to be influenced by host plant species and by a number
		Known diazotrophs are as follows: [1] Vibrio diazotrophicus, [2] Azospirillum brasilense, [3] Azotobacter chroococcum, [4] Klebsiella pneumoniae, [5] Azospirillum lipoferum, [6] Azotobacter diazotrophicus, [7] Rhizobium meliloti, [8] Rhizobium leguminosarum, and [9] Azotobacter vinlandii.
		diversity of diazotrophs in the rhizospheres of salt marsh grasses.
	aem.highwire.org /cgi/content/full/64/11/4276 (4168 words)

	UM Extension: Minnesota Crop eNews
		The first rhizosphere diatroph was identified as early as 1925 and in the 1960s and 1970s researchers were very optimistic about the potential of these associative diazotrophs to provide nitrogen to crops other than legumes.
		The amount of nitrogen fixed appears to be low and the mechanism to make the N available to the plant appears to rely or death and decay of the bacterial biomass rather than excretion of the accumulated N as is the case with the Rhizobium spp.
		In summary, the authors concluded that, although associative diazotrophs held promise, the practical application were limited until such time that results were more repeatable and predictable.
	www.extension.umn.edu /cropenews/2006/06MNCN22.htm (609 words)

	SURVEY OF INDIGENOUS DIAZOTROPHIC BACTERIA ASSOCIATED TO MAIZE IN URUGUAY (Site not responding. Last check: 2007-09-16)
		Summary Diazotrophs have been cultured from both the plant interior and root environment of maize.
		In addition to N2 fixation, associative diazotrophs exert their positive effects on plant growth directly or indirectly through a combination of different mechanisms.
		Indirectly, diazotrophs are able to decrease or prevent the deleterious effects of pathogenic microorganisms, mostly through the synthesis of antibiotics and/or fungicidal compounds, through competition for nutrients or by the induction of systemic resistance to pathogens.
	www.cin.edu.uy /lms/diazotroficos.htm (1601 words)

	Title page for ETD etd-11152004-132003
		Trichodesmium is a globally significant marine diazotroph responsible for supplying new nitrogen to the oligotrophic regions in which it is found.
		A field study of this diazotroph shows that nitrogen fixation scales with light intensity from a maximum at 50% surface irradiance.
		Our work established that this diazotroph is ecologically important in the water column of the Gulf of Mexico, with important implications for nitrogen and carbon cycling.
	etd.gatech.edu /theses/available/etd-11152004-132003 (357 words)

	Intel STS Results \| Science Service
		Ashleigh Brooks Theberge, 17, of Orr's Island, studied the effects of a widely used herbicide on nitrogen-fixing bacteria for the environmental science project she entered in the Intel Science Talent Search.
		A plaque in Utah's Arches National Park and a passage in Rachel Carson's Silent Spring had piqued her interest in these organisms (diazotrophs), which enhance soil fertility by increasing usable nitrogen.
		Based on a series of clover, soybean and diazotroph studies, she concluded that treatments with a popular herbicide caused a general decrease of activity in soil bacteria, indicating a possible harmful side effect that should be investigated further.
	www.sciserv.org /sts/61sts/Theberge.asp (195 words)

	Transformation studies for increasing salt tolerance and nitrogen fixation in Azospirillum halopraeferens (Site not responding. Last check: 2007-09-16)
		But, survival of Azospirillum and their proliferation in coastal saline soils are much prohibited due to accumulation of unfavourable salts in the soil.
		There is an increasing trend of salinity in soils or in irrigation water especially in coastal regions, which created the necessity in search of this plant associated diazotrophs showing salt tolerance and capable of existing in higher saline conditions.
		A number of diazortrophic bacteria were isolated from the roots of Leptochloa fusca locally known as Kallar grass growing luxuriantly in high saline, low fertile soils of Pakistan and some of them were identified as salt tolerant Azospirillum(17,4,22).
	www.osmania.ac.in /MicroBiology/8p01.htm (572 words)

	abstract 1.142
		Diazotroph abundance and diversity during a large bloom in the oligotrophic North Pacific Gyre
		Microscopic analyses revealed the bloom was dominated by a diverse assemblage of diatoms, and unicellular and heterocystous cyanobacteria.
		Samples were collected for DNA and RNA analyses of nifH gene abundances, expression, and diversity to assess the distributions and activities of nitrogen fixers (diazotrophs) along a transect from the observed center of the bloom.
	hahana.soest.hawaii.edu /hot/abstracts/doc1_142.html (302 words)

	Differentiation of plasmids in marine diazotroph assemblages determined by randomly amplified polymorphic DNA analysis ...
		Bagwell, C. and Lovell, C. Microdiversity of culturable diazotrophs from the rhizoplanes of the salt marsh grasses Spartina alterniflora and Juncus roemerianus.
		Bergholz, P. W., Bagwell, C. and Lovell, C. Physiological diversity of rhizoplane diazotrophs of the saltmeadow cordgrass, Spartina patens: implications for host specific ecotypes.
		Piceno, Y. M., Noble, P. and Lovell, C. Spatial and temporal assessment of diazotroph assemblage composition in vegetated salt marsh sediments using denaturing gradient gel electrophoresis analysis.
	mic.sgmjournals.org /cgi/content/full/148/1/179 (4823 words)

	DIALOG Dissertation Abstracts (Site not responding. Last check: 2007-09-16)
		Despite a growing awareness of their role in microbial food webs, there is little experimental or observational evidence of the role of viruses in shaping marine bacterial assemblages.
		Moreover, enhancement of viral pressure had no discernable impact upon the relative dominance of common microbial fingerprint components in plankton, but significant negative impacts on common components matched with significant positive impacts on rarer components in sediment experiments.
		Correlation analysis of viral parameters and the abundance, productivity, relative richness and diversity of bacterioplankton and diazotrophs indicate that overall diversity of host assemblages may be related to their habitat and resource availability, but viruses have significant impacts upon their assemblages within habitats.
	aslo.org /phd/dialog/200503-14.html (354 words)

	IngentaConnect Effects of model root exudates on structure and activity of a soi...
		Nitrogen fixation is often enhanced in the rhizosphere as compared with bulk soil, due to asymbiotic microorganisms utilizing root exudates as an energy source.
		We have studied the activity and composition of asymbiotic soil diazotrophs following pulse additions of artificial root exudates and single carbon sources, simulating the situation of bulk soil coming into contact with exudates from growing roots.
		The population of potential diazotrophs was studied using universal and group-specific nifH polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analysis.
	www.ingentaconnect.com /content/bsc/emi/2005/00000007/00000011/art00005 (322 words)

	Diatom Diazotroph Assemblages II Posters - Ocean Sciences [OS]
		The diazotrophic cyanobacterium {\it Trichodesmium} is capable of fixing both CO$_{2}$ and N$_{2}$ concurrently throughout the day yet it does not contain heterocysts.
		Marine wood-boring bivalves, or shipworms, harbor a polysymbiosis of cellulolytic and diazotrophic bacteria in gill bacteriocytes that allows the host to live on a nitrogen-poor diet composed only of wood.
		In combination with molecular assays of diazotroph community structure, our results indicate that diazotroph abundance is a major determinant of nitrogen fixation rate, and that different diazotroph groups have very different cell-specific rates of nitrogen fixation.
	www.agu.org /meetings/os06/os06-sessions/os06_OS36F.html (3547 words)

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