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  • 1
    Electronic Resource
    Electronic Resource
    Growth characteristics of selected mutants of a coccoid blue-green alga (1970)
    Springer
    Archives of microbiology 72 (1970), S. 1-8 
    Details
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary After exposure of cells to N-methyl-N′-nitro-N-nitrosoguanidine a series of stable mutants of the marine coccoid blue-green alga, Agmenellum quadruplicatum, were isolated. 1. Two of these mutants were blocked at nitrate reductase and required nitrite or ammonium ion for growth. 2. Four of the mutants were blocked at nitrite reductase, required NH4 + for growth but had a functional nitrate reductase. These mutants readily reduced NO3 - to NO2 -. 3. Two of the mutants had altered phycocyanin/chlorophyll a ratios, together with slightly impaired growth rates. 4. Mutant AQ-19 responded to casamino acids and possibly represents an amino acid auxotroph.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411008
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of nitrogen limitation on the ultrastructure of the cyanobacterium Agmenellum quadruplicatum (1981)
    Springer
    Archives of microbiology 130 (1981), S. 204-212 
    Details
    ISSN: 1432-072X
    Keywords: Agmenellum quadruplicatum ; Nitrogen starvation ; Ultrastructure ; PATO poststain ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nitrogen limitation on the ultrastructure of the unicellular cyanobacterium, Agmenellum quadruplicatum, were studied by thin sectioning transmission electron microscopy. Nitrogen became limiting for growth 14–15 h after transfer to nitrogen-limiting medium, but cultures retained full viability for at least 45 h. The c-phycocyanin: chlorophyll a ratio and cellular nitrogen content of the culture dropped rapidly after 14–15 h, as a progressive deterioration of major cell structures took place. Phycobilisomes were degraded first, followed by ribosomes and, then, thylakoid membranes. These structures were virtually depleted from the cells within 26 h. Intracellular polysaccharide accumulated in place of the normal cell structures throughout this period. Nitrogen limitation did not affect polyphosphate bodies, carboxysomes, lipid granules, the cell envelope, or the extra-cellular glycocalyx. All of the ultrastructural changes resulting from nitrogen limitation were reversed upon addition of nitrate to a starved culture. Most cell structures were restored within 3 h, and restoration was complete within 9 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00459520
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  • 3
    Electronic Resource
    Electronic Resource
    A survey of available nitrogen sources for the growth of the blue-green alga, Agmenellum quadruplicatum (1975)
    Springer
    Archives of microbiology 104 (1975), S. 135-138 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen Sources ; Blue-Green Alga ; Growth ; Agmenellum quadruplicatum ; Amino Acids ; Purines ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth response of the marine blue-green alga, Agmenellum quadruplicatum to 60 inorganic and organic nitrogen sources was studied. These compounds were offered as sole nitrogen sources. Most amino acids, most purines, and urea were good nitrogen sources for growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447313
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  • 4
    Electronic Resource
    Electronic Resource
    Glycocalyx of Agmenellum quadruplicatum (1980)
    Springer
    Archives of microbiology 128 (1980), S. 8-11 
    Details
    ISSN: 1432-072X
    Keywords: Agmenellum quadruplicatum ; Glycocalyx ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine cyanobacterium Agmenellum quadruplicatum was shown to possess an extracellular glycocalyx similar in structure to those surrounding other bacteria from a variety of natural environments. Thin sections of cells stained with ruthenium red and frozen-etched preparations of unfixed cells indicated the glycocalyx was a network of small fibrils. The glycocalyx was present during all phases of growth, and was not degraded during nutrient limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422298
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of the cyanobacterium,Mastigocladus laminosus (1982)
    Springer
    Archives of microbiology 133 (1982), S. 11-19 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Ultrastructure ; Mastigocladus laminosus ; Fischerella ; True branching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphology and ultrastructure of the thermophilic cyanobacteriumMastigocladus laminosus were examined by scanning and transmission electron microscopy. Mature cultures consisted of relatively old, wide filaments that branched frequently to form younger, thinner filaments. The cells of the younger filaments had a consistently cylindrical morphology, while those of older filaments were rounded and pleomorphic. The internal ultrastructure of the cells depended somewhat on their age. As young cells became larger and wider, their thylakoids underwent slight rearrangement and spread out toward the center of the cytoplasm. Polyphosphate bodies, carboxysomes (polyhedral bodies), and lipid-body-like structures increased in number as the cells aged, but ribosomes and cyanophycin granules were depleted. Cell division involved septum formation followed by ingrowth of the outer membrane and sheath. Cells in older filaments were separated from each other by a complete layer of sheath material. Septum formation in older cells was also seen to occur parallel to the long axis of the filament, thereby confirming that true branching took place.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00943762
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  • 6
    Electronic Resource
    Electronic Resource
    Morphology and ultrastructure of the cyanobacterium Mastigocladus laminosus growing under nitrogen-fixing conditions (1984)
    Springer
    Archives of microbiology 137 (1984), S. 97-103 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Heterocysts ; Utrastructure ; Cytology ; Akinetes ; Mastigocladus laminosus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphological and ultrastructural characteristics of the cyanobacterium Mastigocladus laminosus growing under N2-fixing conditions were examined with light and electron microscopy. Vegetative cells in narrow filaments contained randomly arranged segments of thylakoid membrane, centrally located carboxysomes (polyhedral bodies), peripherally located lipid bodies, and large numbers of polysaccharide granules in addition to nuclear material and ribosomes. The ultrastructural characteristics of cells in wide filaments were similar, except for increased numbers of carboxysomes and lipid bodies. Heterocytes and proheterocysts developed at a variety of locations in narrow filaments, wide filaments, and the lateral branches off of wide filaments. Akinetes were not observed in any of the filaments. The morphological characteristics of heterocysts and proheterocysts were variable and depended on those of the vegative cells from which the heterocysts and proheterocysts developed. Mature M. laminosus heterocysts were somewhat similar to those formed in other cyanobacterial genera, but they possessed a number of distinct and unique ultrastructural characteristics, including (i) the absence of a fibrous and, possibly, a laminated wall layer, (ii) the presence many closely packed membranes throughout most of the cytoplasm, and (iii) the presence of unidentified, spherical inclusion bodies of variable electron density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414447
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  • 7
    Electronic Resource
    Electronic Resource
    Nodulation and symbiotic nitrogen fixation of cowpea (Vigna unguiculata (L.) Walp) (1987)
    Springer
    Plant and soil 99 (1987), S. 435-439 
    Details
    ISSN: 1573-5036
    Keywords: Cowpea ; Effective nodulation ; Nitrogen fixation ; Nodule growth ; Plant age ; Rhizobium strain ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rhizobium strains CIAT 301, CIAT 79 and SLM 602 were tested and found effective in the nodulation and nitrogen fixation of cowpea cv. MI-35 (Vigna unguiculata (L.) Walp) plants in growth chamber experiments. Fresh weight of nodules increased with plant age initially and stabilized in 20–30 days from planting, followed by a secondary flush of nodule growth after 30 days. Apparent nitrogen fixation per gram nodule fresh weight reached a maximum in 20–30 days after planting and then decreased, even though a flush of new nodules was produced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370888
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  • 8
    Electronic Resource
    Electronic Resource
    Isolation and characterization of five genotypic mutants of chlorate-resistant cyanobacteria unable to utilize nitrate (1994)
    Springer
    Current microbiology 29 (1994), S. 311-318 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Spontaneous mutants of the cyanobacteriumSynechococcus PCC 7002 resistant to chlorate were isolated. Either 40mM or 400mM Na2ClO3 was used as the selective agent. Putative Chlr colonies were picked onto medium containing ammonia as the sole N source, then replicaplated to media containing either NH4 +, NO2 − as N sources. Of 252 putative mutants, 106 were able to use either NH4Cl or NaNO2 but not NaNO3 as their sole source of nitrogen. All of the mutant isolates had generation times similar to wild-type 7002 when grown on either ammonium (3.8–4.1 h/generation) or nitrite (4.5–4.7 h/generation). None had detectable methyl viologensupported nitrate reductase activity and are thus phenotypically NRase−. The Chlr mutants had photomediated O2 production and dark O2 uptake rates similar to the wild type and responded similarly to selected metabolic inhibitors. They expressed increased levels of phycocyanin (PC) synthesis under normal, nitrogen-replete growth conditions, but rapidly lapsed into a chlorotic state upon a shift to either medium containing nitrate or to N-free medium. Genetic analysis of the Chl4 mutants indicated that each could be rescued by direct transformation with chromosomally derived DNA from the wild-type strain. Frequencies of transformation for the mutants were characteristic for single genetic lesions in this cyanobacterium. On the basis of marker rescue by a cosmid library of wild-type DNA, the NRase− mutants could be grouped into five distinctive genotypic families.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570222
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