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  • 11
    ISSN: 1432-072X
    Keywords: Schizophyllum commune ; Basidiospore germination ; Polyol dehydrogenases ; Polyacrylamide dise gel electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Enzymes of polyol metabolism were studied in basidiospore germination of Schizophyllum commune during periods of in vivo arabitol and mannitol pool depletion (growth on glucose-asparagine) and during their subsequent synthesis (growth on acetate-NH 4 + ). Optimal conditions for assays were established and specific activities of enzymes employing d-arabitol, d-mannitol, d-ribulose, d-fructose and d-xylulose as substrates were traced. Inquiries into the products formed during these reactions showed that d-ribulose generated arabitol while d-fructose produced mannitol with d-xylulose giving rise to xylitol. The dehydrogenase reactions were further investigated using polyacrylamide disc gel electrophoresis. Here was revealed the existence of at least two separate enzymatic activities pertaining to the catabolism of arabitol and mannitol. Also noted were the electrophoretic patterns when d-sorbitol, ribitol, xylitol and ethanol were used as substrates.
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  • 12
    ISSN: 1432-072X
    Keywords: Pyruvate fermentation ; Rhodospirillum rubrum ; Pyruvate formate lyase ; Formate hydrogen lyase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fermentative metabolism of Rhodospirillum rubrum (strain Ha, F1, S1) was studied after transfering the cells from aerobic to anaerobic dark culture conditions. Pyruvate was metabolized mainly to acetate and formate, and to a lesser extent to CO2 and propionate, by all strains. Therefore, pyruvate formate lyase would appear to be the characteristic key enzyme of the dark anaerobic fermentation metabolism in R. rubrum. Strain F1 and S1 metabolized the formate further to H2 and CO2. It is concluded that this cleavage was catalysed by a formate hydrogen lyase system. Strain Ha was unable to metabolize formate. The cleavage of formate and the synthesis of poly-β-hydroxy-butyric acid were increased by a low pH value (∼6.5). Fermentation equations and schemes of the pyruvate metabolism are discussed.
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  • 13
    ISSN: 1432-072X
    Keywords: Blue-green alga Gloeocapsa alpicola and near UV radiation ; Gloeocapsa alpicola and near UV radiation ; Pigmentation changes in Gloeocapsa alpicola due to near UV radiation ; Near UV radiation, changes in pigmentation in Gloeocapsa alpicola due to
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The UV survival characteristics of a wildtype and a UV resistant strain of Gloeocapsa alpicola were compared. Except for a higher carotenoid content the resistant strain was similar to the wild-type. However, on exposure to UV radiation the level of carotenoids in the wild-type fell sharply whereas no such decrease occurred in the resistant strain. Growth of cells in diphenylamine and under red and blue light reduced the survival rate. This phenomenon is linked with a reduced carotenoid level in the cell, indicating that they perform an important protective function.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 107 (1976), S. 109-111 
    ISSN: 1432-072X
    Keywords: Halophilism ; Blue-green alga ; Cyanobacteria ; Aphanotece halophytica ; Salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The isolation of a halophilic blue-green alga, Aphanothece halophytica, from Great Salt Lake is described. The organism was cultured from waters with salinities up to saturated NaCl (about 30% w/v). It has an optimum salinity for growth of about 16% NaCl, but can grow very slowly even in saturated NaCl. Based on the study of the Great Salt Lake organism, and on a review of the earlier literature, it is concluded that despite recent reports to the contrary, true halophilic blue-green algae do exist.
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  • 15
    ISSN: 1432-072X
    Keywords: Achlya ; Electron microscopy ; Nuclear microfilaments ; Antheridia ; Mycology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This is the first report of intranuclear microfilaments within gametangial nuclei of oömycetous fungi. Longitudinal sections of four to six microfilaments were frequently observed in meiotic antheridial nuclei of Achlya ambisexualis. Each microfilament measured approximately 7–10 nm in diameter. Spindle tubules (25 nm in diameter) were also observed within some of the nuclei possessing microfilaments.
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  • 16
    ISSN: 1432-072X
    Keywords: Cultured Rhizobium ; Nitrogenase activity ; Nutritional requirements ; Temperature ; Oxygen ; Acetylene reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nutritional and physical conditions affecting nitrogenase activity in the strain of “cowpea” rhizobia, 32H1, were examined using cultures grown on agar medium. Arabinose in the basic medium (CS7) could be replaced by ribose, xylose, or glycerol, but mannitol, glucose, sucrose, or galactose only supported low nitrogenase (C2H2 reduction) activity. Succinate could be replaced by pyruvate, fumarate, malate, or 2-oxoglutarate, but without any carboxylic acid, nitrogenase activity was low or undetectable unless a high level of arabinose was provided. Inositol was not essential. Several nitrogen sources could replace glutamine including glutamate, urea, (NH4)2SO4 and asparagine. The maximum nitrogenase activity of cultures grown in air at 30°C was observed under assay conditions of pO2=0.20–0.25 atm and 30°C incubation. Greatest activity occurred after a period of rapid bacterial growth, when viable cell count was relatively constant. Compared with results obtained on the CS7 medium, nitrogenase activity could be substantially increased and/or sustained for longer periods of time by using 12.5 mM succinate and 100 mM arabinose, by increasing phosphate concentration from 2 to 30–50 mM, or by culturing the bacteria at 25°C.
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  • 17
    ISSN: 1432-072X
    Keywords: Bdellovibrio ; Spirillum ; Cell wall ; Bdelloplast ; Lipoprotein ; Peptidoglycan ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In both freeze-etched and critical-point dried preparations examined by transmission and scanning electron microscopy, respectively, the outer surfaces of the cells of Spirillum serpens VHL assume a wrinkled appearance 10–15 min after challenge by Bdellovibrion bacteriovorus 109D. This wrinkling effect is believed (on circumstantial evidence) to be caused by the bdellovibrio's disruption of the cell wall lipoprotein of the Spirillum. With the exception of those topological changes caused by wrinkling, the outer membrane of the Spirillum cell wall retains a normal appearance as viewed in freeze-etched preparations, even after the Spirillum cell has been converted into a bdelloplast. Although the peptidoglycan layer of the Spirillum cell presumably is weakened somewhat by the invading Bdellovibrio, evidence obtained from freeze-fractured preparations of Spirillum bdelloplasts suggests that the peptidoglycan remains as a discrete cell wall layer, even though the Spirillum cell wall apparently has lost much of its rigidity. That the peptidoglycan backbone remains essentially intact, even after the Spirillum cell has been entered by the Bdellovibrio, is supported by the observation that the soluble amino sugar content of the culture medium, as determined by chemical analysis, does not rise even 5.0 h after the association of the Bdellovibrio with the Spirillum has begun.
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  • 18
    ISSN: 1432-072X
    Keywords: Candida utilis ; Potassium-limitation ; Continuous culture ; Oxidative phosphorylation ; Yield values
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When grown in a defined simple salts medium, plus vitamins, Candida utilis displayed an absolute requirement for potassium. But the potassium content of this yeast was exceedingly variable and, with aerobic chemostat cultures (grown at a dilution rate of 0.1 h-1; 30° C; pH 5.5), was low (〈 0.2%, w/w) when they were potassium-limited and high (〉 2%, w/2) when glucose-limited. With potassium-limited cultures, the cell-bound potassium content also varied markedly with growth rate, though hardly at all with glucose-limited cultures; magnesium- and phosphate-limited cultures gave intermediate responses. Changes in cell-bound potassium content correlated only weakly with changes in the cellular contents of magnesium, phosphate and RNA, but strongly with changes in both the Y glucose and Y O values, indicating an involvement of potassium in the generation of energy by oxidative phosphorylation reactions and/or the utilization of this energy for growth processes. Studies with isolated mitochondria revealed that potassium-limited organisms had a changed content of cytochrome b relative to cytochrome a, and lacked coupling at either site 2 or site 3 of the respiratory chain. These results are discussed in relation to the reported functions of potassium in the growth of micro-organisms, and the organizational differences between prokaryotic and eukaryotic cells.
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  • 19
    ISSN: 1432-072X
    Keywords: Non-legume ; Trema sp. ; Rhizobium ; Nodule ; Structure ; Light microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structure of the nodules formed by Rhizobium on the non-legume Trema cannabina var. scabra was studied using the light microscope. The overall features of the nodules showed greater resemblance to the non-legume rather than the legume nodule. Nodule squashes yielded bundles of “infection threads” and “bacteroids” with morphological differences from rhizobial cells grown on yeast-mannitol-glucose agar. Two types of cell infection occurred within the bacterial zone; plant cells were either, like legumes, filled with rhizobia released from the infection threads (less than one third of infected cells) or were filled with the extensive growth and development of the “infection thread”. The rate of nitrogen fixation in the Trema nodule was high. It seemed that host cells filled with threads were active in N fixation.
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  • 20
    ISSN: 1432-072X
    Keywords: Trichoderma viride ; Polyoxin D ; Mycelial walls ; Aberrant tubes ; Cell wall synthesis ; Spore germination ; Morphological development ; Regenerating protoplasts ; Chitin ; β-(1-3) Glucan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When polyoxin D is added to a spore suspension of Trichoderma viride at a concentration from 50–100 μg/ml, it inhibits from 40–60% of germination. This percentage increases if dimethylsulfoxide (DMSO) is added. Mycelium growing in the presence of polyoxin D becomes irregular and loses its rigidity, showing several bulges along the hypha. Under the electron microscope the features of the cell wall and cytoplasmic content are apparently normal. Nevertheless, after incubation with different lytic systems or with (14C)glucose, it can be seen that polyoxin D partially inhibits the biosynthesis of β-(1-3)glucan and the biosynthesis of chitin to a greater extent attaining inhibition of 83% at 100 μg/ml of the antibiotic concentration. Regenerating protoplasts are less affected by polyoxin D. They do regenerate slower but the percentage of regeneration is more than 80%. Aberrant tubes synthesized by these protoplasts are not affected, they manifest their usual morphology and lack of chitin is confirmed in their composition.
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