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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 67 (1969), S. 62-70 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cell differentiation in Anabaena cylindrica is accompanied with characteristic changes in the pigment composition of heterocysts and spores. In both the absence of phycocyanin is consistent with the lack of CO2-fixing ability previously reported. The presence of chlorophyll and β-carotene suggests a functional photosystem I in heterocysts. In the spores chlorophyll is largely replaced by pheophytin. The quantitative distribution of carotenoids is also affected. An increase in the proportion of β-carotene is characteristic of heterocysts while spores show a larger proportion of xanthophylls compared with the intact filament.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Heterocysts reduce triphenyl tetrazolium chloride (TTC) faster than vegetative cells apparently because the absence of the O2-evolving photosystem II and the high electron transport activity in these cells. Although the rate of TTC reduction in vegetative cells is increased by the continuous removal of O2 evolved in photosynthesis, it has not been possible to obtain rates of TTC reduction comparable with those in heterocysts probably because of the continued competition for electrons between TTC and O2. The use of nitro-blue tetrazolium chloride (NBT) as a redox indicator has revealed the presence in filaments under aerobic conditions of a gradient of electron transport activity with strongest reducing power in the heterocysts, proheterocysts and vegetative cells next to heterocysts, and with gradually diminishing activity midway between two heterocysts. This pattern is indistinct in filaments grown under micro-aerophilic conditions. The strong electron transport activity in vegetative cells adjacent to heterocysts appears to promote reducing conditions in the heterocysts. Both, red-formazan formation in the heterocysts and blue-formazan deposition in vegetative cells greatly inhibit nitrogenase activity, and this was adversely affected also by the detachment of heterocysts from vegetative cells. The findings are consistent with the idea that the association of heterocysts with vegetative cells in essential for nitrogen fixation to occur in heterocystous blue-green algae.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 96 (1974), S. 271-279 
    ISSN: 1432-072X
    Keywords: Anabaena cylindrica ; Nitrogen Starvation ; Pigmentation ; Ultrastructure ; Heterocyst Differentiation ; Nitrogenase Activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen starvation, effected by incubating a culture ofAnabaena cylindrica in a medium free from combined nitrogen and under an atmosphere of 1% CO2 in argon, leads to rapid and characteristic changes in the appearance, structure and function of the alga. Change of colour, due apparently to a decrease in the amounts of nitrogenous pigments, is accompanied by a structural transformation of vegetative cells: cyanophycin granules and polyhedral bodies disintegrate, lipid and glycogen accumulate, and large membrane-bound spaces form by means of thylakoid swelling and vesiculation. The rate of heterocyst differentiation and nitrogenase activity is increased. These changes are fully reversed on addition of ammonia to the culture. It appears that thylakoids reform by coalescence of small vesicles assembled in the intrathylakoidal space. Rapid ammonia assimilation is indicated by ample formation of cyanophycin granules in vegetative cells and of “plugs” in the heterocysts.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 99 (1974), S. 221-230 
    ISSN: 1432-072X
    Keywords: Anabaena cylindrica ; Molybdenum ; Vanadium ; Nitrogenase ; Ultrastructure ; Storage Products ; Heterocyst Frequency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural and functional symptoms of molybdenum deficiency inAnabaena cylindrica grown in a medium without combined nitrogen and thus dependent on fixation of elemental nitrogen, resemble those brought about by nitrogen starvation. However, the substantially increased rate of heterocyst differentiation in this culture is not accompanied by a corresponding increase in nitrogenase activity; on the contrary, enzyme activity is severely impaired in the absence of molybdenum. When the supply of molybdenum, or of ammonia, is restored, the alga recovers rapidly. Vanadium exerts an inhibitory effect upon nitrogen-fixing ability of the alga, and its presence in the molybdenum-deficient culture results in the amplification of the symptoms of mlybdenum deficiency.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 279 (1979), S. 527-529 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Three sponges, two containing cyanobacteria and one without, were collected from illuminated habitats at a depth of 6-7 m on Harvey Reef adjacent to Port Sudan. The consistent presence of unicellular cyanobacteria, similar to those observed in other coral reef sponges5, was confirmed by electron ...
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