Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    ISSN: 1432-072X
    Keywords: Oscillatoria ; Cyanobacteria ; Glycogen ; Trehalose ; Fermentation ; Lactate ; Ethanol ; Acetate ; Sulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine nitrogen-fixing cyanobacterium Oscillatoria limosa, strain 23 (Oldenburg) was investigated with respect to its dark anaerobic metabolism. As soon as the cells were incubated anaerobically in the dark, they started to ferment. Glycogen was presumably degraded via the heterolactic fermentative pathway. Glycogen-glucose was degraded to equimolar amounts of lactate, ethanol and carbon dioxide. The disaccharide trehalose, which serves as an osmoprotectant in O. limosa, was also catabolized. Most probably, this compound was fermented almost exclusively to acetate. Some hydrogen was produced as well. In the presence of elemental sulfur, fermentative hydrogen production ceased and sulfide was produced instead. The presence of elemental sulfur had no effect on the amounts and ratios of the fermentation products produced.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Fermentation ; Lactate ; Acetate ; Ethanol ; Glycollate ; Formate ; Oxalate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An arbitrarily chosen selection of 37 cyanobacterial strains of the Oldenburg culture collection were tested for their ability of fermentation and secretion of fermentation products. In all examined strains at least one fermentation product could be detected. For the most part fermentation products were only shed in traces. Thus, for a large part of the investigated strains fermentation does not seem to be a sufficient metabolism to survive dark and anaerobic periods. Only five strains secreted remarkable amounts of products. Glycollate was mostly found in combination with formate and/or traces of oxalate. Lactate, ethanol and acetate were found in combination or single. Most of those strains sheding high amounts of glycollate and formate, did not show a remarkable lactate, ethanol or acetate excretion; those excreting high amounts of lactate, ethanol or acetate produced only minor volumes of glycollate and formate. It was not possible to find similar fermentation patterns by comparing fermentation of species belonging to the same family. Organisms fermenting or not fermenting could be found among marine, brackish and freshwater cyanobacteria. Fermentation, therefore seems to be a unique, and likely old capability among cyanobacteria, which was partly lost during evolution.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 1432-072X
    Keywords: Oscillatoria ; Cyanobacteria ; Nitrogen fixation ; Oxygen protection of N2-ase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oscillatoria sp. strain 23 is a filamentous, non-heterocystous cyanobacterium that fixes nitrogen aerobically. Although, in this organism nitrogenase is inactivated by oxygen a high tolerance is observed. Up to a pO2 of 0.15 atm, oxygen does not have any measurable effects on acetylene reduction. Higher concentrations of oxygen inhibited the activity to a relatively high degree. Evidence for two mechanisms of oxygen protection of nitrogenase in this cyanobacterium was obtained. A high rate of synthesis of nitrogenase may allow the organism to maintain a certain amount of active enzyme under aerobic conditions. Secondly, a switch off/on mechanism may reversibly convert the active enzyme into a non-active form which is insensitive to oxygen inactivation after a sudden and short-term exposure to high oxygen concentrations. It is conceived that these mechanisms in addition to a temporal separation of nitrogen fixation from oxygenic photosynthesis sufficiently explain the regulation process of aerobic nitrogen fixation in this organism.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 14
    ISSN: 1432-072X
    Keywords: Plectonema boryanum ; N2-fixation ; Exponential growth ; Microaerobiosis ; Light ; Pigments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Strains of filamentous, non-heterocystous cyanobacteria from the Pasteur Culture Collection (PCC), able to synthesize nitrogenase under anaerobic test conditions, were tested for growth with N2 as sole nitrogen source at low O2 partial pressure (less than 0.05%). Plectonema boryanum (PCC 73110) exhibited exponential growth under these conditions. This capacity was restricted to light intensities not exceeding 500 lux. Growth rates were 0.014/h at 200 and 0.023 at 500 lux and similar to those of anaerobic and aerobic control cultures with nitrate as N-source. For N2-fixing cultures incubated at 200 and 500 lux, acetylene reduction rates were 4–8 and 5–14 nmol C2H4 per mg protein per min, respectively. The ratio of phycocyanine to chlorophyll was higher (200 lux) or slightly reduced (500 lux) in N2-fixing cultures as compared to control cultures with nitrate as N-source. On the basis of epifluorescence microscopy and microfluorimetry, no differences in pigment contents were found between individual cells or filaments of N2-fixing cultures. Also no noteworthy differences were observed between the pycobiliprotein composition of individual cells in N2 fixing cultures as compared to nitrate-grown controls. Thus the observed exponential growth of P. boryanum at low light intensities implies simultaneous nitrogen fixation and oxygenic photosynthesis. Additional continuous culture experiments showed that N2-fixing exponential growth was dependent on O2 partial pressures lower than 0.2–0.4%. The other strains tested (PCC 6412, 6602, 7403, 7104) did not grow under such conditions.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 1432-072X
    Keywords: Key words Cyanobacteria ; Merismopedia ; Synechococcus ; Synechocystis ; Eucapsis ; 16S rDNA ; sequencing ; SDS-PAGE ; Taxonomy ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five Merismopedia-like cyanobacterial strains were collected from microbial mats at Norderney Island, subcultured in the laboratory, and finally grown as unicyanobacterial cultures. As a sixth strain, Merismopedia glauca from the „Sammlung von Algenkulturen“ at Göttingen (SAG) was used for comparisons. According to morphological and physiological characteristics initially observed in the field and during initial subculturing, the five strains were assigned to the species Merismopedia glauca, Merismopedia punctata, or Merismopedia elegans. However, after prolonged maintenance under laboratory conditions, the formation of platelet-like colonies stopped, whereas cell sizes, production of extracellular polymeric substances, and division patterns were stably maintained. These physiological and morphological parameters allowed us to divide the six strains into two clusters. This division was further supported by the profiling of total cell protein and phycobilisomes using SDS-PAGE. The nearly complete 16S rDNA sequence of three of the six isolates was determined. The comparative sequencing analysis revealed an almost 100% identity of these three Merismopedia-like strains. The evolutionary distance dendrogram constructed placed this Merismopedia cluster into a common line of descent with Synechocystis sp. strain PCC6906. Based on the analysis of common stretches of 1,050 nucleotides, the overall similarity between the sequence types of „Merismopedia“ and „Synechocystis“ is 96–97%. The values of the different methods for taxonomic classification of unicyanobacterial strains, the relationship of the cyanobacterial genera Merismopedia, Synechococcus, Synechocystis, and Eucapsis sp., and the functional role of different Merismopedia morphologies within microbial mats are discussed. It is suggested that all analyzed Merismopedia strains be combined into one species, namely Merismopedia punctata Meyen (1839).
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 1432-072X
    Keywords: Key words Actinomycetes ; Acidothermus cellulolyticus ; Arthrobacter ; Bacillus ; Frankia ; Geodermatophilus ; Sporichthya polymorpha ; 16S rDNA sequences ; Rock ; varnish ; Multilocular thallus ; Biodiversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an extended study on the biodiversity of rock-dwelling bacteria, the colony and cell morphology, physiology, protein patterns, and 16S rDNA sequences of 17 bacterial strains isolated from different surfaces of rocks, stones, and monuments and from various geographical locations were characterized. All except one strain, which was found to be a Bacillus, were members of the order Actinomycetales. The majority of the strains either were closely related to Geodermatophilus obscurus, which was also analyzed in this study, or formed a closely related sister taxon. All of these strains were isolated from the surface of marble in Namibia and Greece and from limestone from the Negev desert, Israel. One strain, G10, of Namibia origin was equidistantly related to Geodermatophilus obscurus, Frankia alni, Sporichthya polymorpha, and Acidothermus cellulolyticus. Three strains from rock varnish in the Mojave desert, California, were found to be highly related to Arthrobacter (formerly Micrococcus) agilis. All clusters could be confirmed from results of studies on morphological and physiological properties and from banding patterns of whole cell proteins. Based on the results of tests, four additional strains were assigned to the lineage defined by strain G10.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Electrochimica Acta 12 (1967), S. 843-853 
    ISSN: 0013-4686
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3185-3192 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculated the steady-state recombination rate for two coupled defect levels and implemented the model into a device simulator. This model generalizes the familiar single-level Shockley–Read–Hall (SRH) formula. If the intercenter transition probability vanishes, it reduces to the sum of two individual SRH rates, which are only linked via the band occupancies. The cases, where one of the levels or even both behave like traps in carrier capture, and the case of a rate-limiting intercenter transition are derived from the general expression. The important feature of the model is a possible increased field effect which might lead to large excess currents. The field effect is discussed in terms of tunnel-assisted multiphonon capture or direct tunneling into the levels, respectively. We show by means of numerical simulation that the large ideality factors found for liquid phase epitaxy grown diodes with weak intrinsic fields can be the result of a rapid direct charge transfer between donors and acceptors and the high probability of tunneling into the hydrogenic states. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 19
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 20
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Cyanobacterial mats developed on fine sandy sediments of the upper littoral of the island of Mellum (North Sea). Freshly colonized sediment was dominated by the non-heterocystous, nitrogen-fixing cyanobacterium Oscillatoria limosa. Well established mats in which the cosmopolitan cyanobacterium Microcoleus chthonoplastes was the dominant organism also usually contained O. limosa as a minor component. This mat was about 1 mm thick and contained high biomass. Photosynthesis was maximal at about 150 μm depth and reached values of 280 μmol oxygen. 1−1 ? min−1. On the other hand, in the dark, high respiratory activity turned the mat anaerobic within minutes. Freshly colonized sediment consisted of low cyanobacterial biomass loosely attached to the sand grains and present up to a depth of 2.5 mm. Respiratory activity was low and the sediment remained aerobic to a depth of 2 mm throughout the night. Nitrogen fixation (acetylene reduction) was measured during 24-h periods in both types of mats in order to elucidate interactions with oxygenic photosynthesis and oxygen concentration. Acetylene reduction in the mats showed very different diurnal patterns which depended on the type of mat investigated and the time of year. The results indicated that a temporary separation of oxygenic photosynthesis and nitrogen fixation occurred in the mat. Established mats fixed nitrogen predominantly during the transition from dark to light and vice versa, when oxygenic photosynthesis was reduced or absent. Freshly colonized sediment-fixed nitrogen throughout the night but often a stimulation was seen at dawn. The latter showed much higher specific activities than the established type. Also in spring, specific activities were much higher.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...