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Topic: Heterocyst

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	Image Gallery
		Anabaena scheremetievi - A slight hint of a sheath is visible.
		Anabaenopsis circularis - The central pair of heterocysts is clearly visible.
		Anabaenopsis circularis - A developing pair of heterocysts is visible in the center of the trichome.
	www-cyanosite.bio.purdue.edu /images/images.html (1191 words)

	Proceedings of the Oklahoma Academy of Science
		The occurrence and position of heterocysts, the criteria used to identify this genus, were shown to be dependent on the source and concentration of N. Vegetative cell to heterocyst ratios increased as the N concentration increased.
		The heterocyst, a specialized cell in the trichomes of the Nostocaceae, is distinguished from vegetative cells by its different size, shape, color, and function (1, 2).
		The position of the heterocyst in the trichome is of taxonomic importance at the generic level (3, 4, 5).
	digital.library.okstate.edu /oas/oas_htm_files/v56/p49_52nf.html (1610 words)

	Please title this page. (Page 2) (Site not responding. Last check: 2007-10-25)
		The unique exception are the heterocysts of filamentous cyanobacteria, which irreversibly have lost this ability for cell division.
		The mature heterocysts distribute the fixed nitrogen in the form of glutamine along the filament while receiving the carbon source sucrose.
		Most researchers involved in unraveling the physiology and molecular biology of heterocyst formation have concentrated on the events leading to nif expression.
	www.uni-bayreuth.de /biologie/senescence/projects.html (221 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: 2007-10-25)
		Heterocysts are specialized nitrogen-fixing cells formed by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale and Anabaena sperica, during nitrogen starvation.
		The lack of photosystem II prevents heterocysts from photosynthesising, so the vegetative cells provide them with carbohydrates, which is thought to be sucrose.
		Once a heterocyst has formed, it cannot revert to a vegetative cell, so this differentiation can be seen as a form of apoptosis.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=heterocyst (424 words)

	Effect on Heterocyst Differentiation of Nitrogen Fixation in Vegetative Cells of the Cyanobacterium Anabaena variabilis ...
		in the heterocysts is transported to vegetative cells in the filament,
		NF-76 (10) is a mutant of FD that fails to differentiate heterocysts
		Walsby, A. The permeability of heterocysts to the gases nitrogen and oxygen.
	jb.asm.org /cgi/content/full/183/1/280 (4779 words)

	[No title] (Site not responding. Last check: 2007-10-25)
		Though the genetic mechanisms governing heterocyst development are largely unknown, there is considerable precedent in other bacterial systems for control at the level of gene transcription.
		Although the regulation of gene expression during heterocyst development undoubtedly occurs at many levels, transcriptional control is believed to play a major role.
		Experiments are proposed to identify cis elements that regulate rbcL expression in vegetative and heterocyst cells, and to begin identification of trans-acting factors that interact with these cis elements.
	www.cs.utexas.edu /users/yguan/NSFAbstracts/Abstracts/BIO/MCB.BIO.a9507490.txt (549 words)

	Stephen Smith
		Finally respiration in the heterocyst is vastly increased compared to vegetative cells, partly to use up any oxygen in the cell.
		Heterocysts also release a diffusible peptide which inhibits nearby cells from differentiating, producing the regular pattern of heterocysts to vegetative cells in the Anabaena filament.
		Heterocysts serve as a simple model of cellular differentiation, and could lead to a better understanding of mechanisms involved with more complex developmental pathways.
	employees.oxy.edu /momartin/microbios/smith.html (429 words)

	Title page for ETD etd-05152006-150909
		This organism has developed a necessary spatial separation of the incompatible processes of photosynthesis and nitrogen fixation, as nitrogen fixation is sensitive to oxygen that is produced during photosynthesis.
		Heterocyst formation occurs about every tenth cell along a filament of photosynthetic vegetative cells after 24-36 hours of nitrogen starvation.
		Both the alr4311 and all4312 mutants appeared to differentiate heterocysts, suggesting that the role of each of these genes may be related to heterocyst function, rather than development of the heterocyst structure.
	www.lib.ncsu.edu /theses/available/etd-05152006-150909 (436 words)

	Curtis Homepage
		Heterocysts are the exclusive sites of nitrogen fixation within the filament and carry out an incomplete photosynthesis relative to neighboring vegetative cells.
		We are interested in how heterocyst development is regulated, in particular how gene expression is controlled during differentiation.
		Additional projects involve the identification and characterization of genes that are up-regulated during heterocyst development.
	www.cals.ncsu.edu /genetics/curtis/curtis.html (326 words)

	1
		Heterocyst provide the oxygen rich environment needed for nitrogen fixation.
		Heterocyst are photosynthetic, thus need large amounts of nitrogen.
		Heterocyst carry the fixed nitrogen into the environment as they decay.
	www.botany.hawaii.edu /nlc_biology/1411/lecture/SamEx3.htm (592 words)

	Anabaena sp. Strain PCC 7120 hetY Gene Influences Heterocyst Development -- Yoon et al. 185 (23): 6995 -- The Journal ...
		Heterocyst suppression by DNA fragments subcloned from cosmid 8E11.
		The heterocyst pattern was determined by microscopic examination of filaments 26 h after induction as previously described (20).
		Inactivation of hetY produced immature and abnormal heterocysts, as shown in photomicrographs of wild-type Anabaena strain PCC 7120 (A and C) and hetY-inactivated strain AMC642 (B and D) taken before (A and B) and 24 h after (C and D) heterocyst induction.
	jb.asm.org /cgi/content/full/185/23/6995 (2587 words)

	Heterocyst spacing - Phenomenon
		Blue cells in this filament of Anabaena PCC 7120 are heterocysts stained with Alcian blue, a dye that binds to heterocyst-specific polysaccharide
		Heterocysts are very expensive to make and to operate, and so they are not present in Anabaena filaments unless required.
		It ensures that expensive heterocysts feed as many vegetative cells fixed nitrogen as possible.
	www.people.vcu.edu /~elhaij/lab/projects/hetspacing-phenom.html (287 words)

	Heterocyst Differentiation and H2 Production in N2-Fixing Cyanobacteria
		Heterocysts obtain carbohydrates from the surrounding vegetative cells, and export fixed nitrogen in return.
		Heterocyst differentiation occurs at the location that ensures the most efficient production and distribution of fixed nitrogen to the surrounding vegetative cells.
		The insights gained on the basic mechanisms of heterocyst differentiation show that the driving force is acting as the trigger for heterocyst differentiation.
	aiche.confex.com /aiche/2005/techprogram/P31823.HTM (1306 words)

	Laboratory Dr. Iris Maldener - Research Interests
		Prospective heterocysts loose the capacity to fix CO, form a special envelope that limits the entrance of O
		This allows the mature heterocyst to generate a microaerobic environment suitable for nitrogenase functioning.
		These heterocysts develop from vegetative cells in a regular pattern along the filament.
	www.uni-regensburg.de /Fakultaeten/nat_Fak_III/Botanik/Maldener/eindex.html (769 words)

	.: Department of Biology: James W. Golden (Site not responding. Last check: 2007-10-25)
		Heterocysts differentiate from vegetative cells at semiregular intervals along the filament and supply fixed nitrogen to neighboring vegetative cells to support their growth.
		Another project in the lab is the use of mutant screens, DNA expression microarrays, and bioinformatics to identify genes involved in the regulation of several aspects of heterocyst differentiation.
		We also have studied the role of RNA polymerase sigma factors in heterocyst development and are interested in identifying the genes that regulate the nitrogen-fixation genes.
	www.bio.tamu.edu /FACMENU/faculty/jgolden.htm (812 words)

	Prof. Haselkorn - Chemistry Department - University of Chicago
		Heterocysts are anaerobic factories for nitrogen fixation; in them, the nitrogenase enzyme complex is synthesized and the components of the oxygen-evolving photosystem II are turned off.
		More than 1000 genes are believed to be differentially expressed during the (irreversible) development of a heterocyst from a vegetative cell.
		Heterocyst differentiation and nitrogen fixation in the cyanobacterium Anabaena.
	chemistry.uchicago.edu /fac/haselkorn.shtml (885 words)

	template
		Heterocysts supply fixed nitrogen to neighboring vegetative cells in return for the products of photosynthesis.
		The differentiation of heterocysts is provoked by an environmental cue, which is the absence of a fixed nitrogen source.
		Heterocysts are terminally differentiated cells that are highly specialized for nitrogen fixation.
	biology.kenyon.edu /courses/biol114/Chap12/Chapter_12.html (1961 words)

	Decastronema kotori gen. nov., comb. nov.: a mat-forming cyanobacterium on Cretaceous carbonate platforms and its ...
		Differentiated heterocysts do not produce EPS and act as anchoring points for trichomes, restricting their gliding inside the sheaths (Golubic et alii, 1996).
		The architecture of the sheaths is consistent with the unique mode of growth, development and differentiation in a small group of modern species among the heterocystous cyanobacteria assigned to the genus Scytonema of the section Myochrotes.
		Heterocystous cyanobacteria, of which Decastronema is one, were reported from Devonian Rhynie chert (Kidston & Lang, 1921), but may have evolved during the Mesoproterozoic, between 1300 and 1500 million years ago, as suggested by the findings of the fossil Archaeoellipsoides, interpreted as akinetes of heterocystous cyanobacteria similar to Anabaena (Golubic et alii, 1995).
	paleopolis.rediris.es /cg/CG2006_A02/index.html (8263 words)

	Cyanophyta lab (Site not responding. Last check: 2007-10-25)
		Anabaena - Fig 1 2, 3, coiled filaments with intercalary heterocysts and akinetes.
		1, 2,3, - tapering filament with a single terminal heterocyst and if present, and adjacent akinete, enclosed in a gelatinous sheath.
		Wasserbluthe - (Water bloom) - Fig 1, 2, 3, a mixture of floating blue-greens which often occur in great profusion when population explosions take place in lakes and ponds.
	www.cs.cuc.edu /~tfutcher/Cyanophytalab.html (260 words)

	Heterocyst1 (Site not responding. Last check: 2007-10-25)
		Diagrammatic representation of carbon and nitrogen exchange between the heterocyst and vegetative cells.
		The heterocyst lacks photosystem II activity, which prevents the formation of oxygen in the vicinity of the oxygen-labile nitrogenase, but also prevents carbon fixation.
		The heterocyst and vegetative cell thus demonstrate an early evolved form of cellular specialization and a division of labour of the type normally associated with higher plants and animals.
	teachline.ls.huji.ac.il /72346/Nitrogen/Heterocyst1.htm (171 words)

	IngentaConnect Heterocyst differentiation and pattern formation in cyanobacteria... (Site not responding. Last check: 2007-10-25)
		Heterocyst differentiation in filamentous cyanobacteria provides an excellent prokaryotic model for studying multicellular behaviour and pattern formation.
		Once heterocyst development has been initiated, interactions among the various components involved in heterocyst differentiation determine the developmental fate of each cell.
		HetR, a protease showing DNA-binding activity, is crucial to heterocyst differentiation and appears to be the central processor of various early signals involved in the developmental process.
	www.ingentaconnect.com /content/bsc/mole/2006/00000059/00000002/art00003 (355 words)

	Expression of the Anabaena hetR gene from a copper-regulated promoter leads to heterocyst differentiation under ...
		Heterocyst differentiation in the filamentous cyanobacterium Anabaena PCC 7120 requires a functional hetR gene.
		The 0.5-h 216 lane is blank, likely to be a result of sample degradation, and the 1.9-kb band in the 216 3.0- and 4.0-h lanes is distorted because of an air bubble during transfer of the RNA.
		The heterocysts can be identified by the low fluorescence attributable to the loss of chlorophyll from photosystem II and the degradation of the phycobiliproteins.
	www.pnas.org /cgi/content/full/98/5/2729 (4036 words)

	Indiana University - Biocomplexity - Events - Workshops - Biocomplexity VI
		strain PCC 7120 produces a developmental pattern of single heterocysts separated by 10 to 15 photosynthetic vegetative cells.
		The patS gene encodes a 13 (or 17) amino acid peptide that is thought to serve as a diffusible cell-to-cell signal that contributes to the regulation of heterocyst pattern by lateral inhibition.
		Overexpression of patS inhibits heterocysts, and a patS deletion mutant forms multiple contiguous heterocysts and abnormally short vegetative cell intervals between heterocysts.
	biocomplexity.indiana.edu /events/archives/ws/biovi/speakers.php?v=abstract&sid=43 (357 words)

	IngentaConnect Regulation of CO2 on heterocyst differentiation and nitrate uptak...
		Regulation of CO on heterocyst differentiation and nitrate uptake in the cyanobacterium Anabaena sp.
		The aim of the present investigation was to study the effects of different inorganic carbon and nitrogen sources on nitrate uptake and heterocyst differentiation in the culture of cyanobacterium Anabaena sp.
		Experimental results showed that the differentiation frequency of heterocysts when the cells were cultivated with elevated CO was higher than that of the cells grown with air or bicarbonate.
	www.ingentaconnect.com /content/bsc/jam/2005/00000098/00000003/art00019 (350 words)

	Anabaena - MicrobeWiki
		This separation of functions is essential because the nitrogen fixing enzyme in heterocysts, nitrogenase, is unstable in the presence of oxygen.
		To prevent the entrance of oxygen into the cell, the developing heterocyst builds three additional layers outside the cell wall, giving it its characteristic enlarged and rounded appearance, thus the rate of oxygen diffusion into heterocysts is 100 times lower than of vegetative cells.
		It is believed that the capacity for developing heterocysts first developed when the concentration of oxygen in the atmosphere (largely produced by cyanobacteria) reached levels high enough to cause the inactivation of the nitrogen-fixing enzyme nitrogenase.
	microbewiki.kenyon.edu /index.php/Anabaena (768 words)

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