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  • Articles  (77)
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  • 1
    Electronic Resource
    Electronic Resource
    A quantitative approach to sedimentary surface structures contoured by the interplay of microbial colonization and physical dynamics (1999)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 46 (1999), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In the tidal flats of Mellum Island (southern North Sea), biofilms and microbial mats, generated largely by cyanobacteria, colonize the sedimentary surfaces. Biostabilization effects and biomass enrichment influence erosional and depositional dynamics resulting from tidal flushing and storm surges. The overlapping of both biological and physical forces causes the development of characteristic sedimentary structures. To obtain a quantitative expression of the degree of effectiveness of microbial colonization in the formation of structures in an extended tidal area, a modification index (MOD-I) was developed based on the following values: (i) the proportion of mat-covered area related to a defined investigation area (IA); (ii) the degree of steepness of slope angles of raised erosional remnants (IS); and (iii) the degree of microbial levelling of a rippled sedimentary surface (IN). The MOD-I was calculated for several defined regions within the study area, and both winter and summer situations were considered. The MOD-I values show, first, that the lower intertidal zone is characterized by index values approaching zero. This implies that microbially induced effects in this zone are negligible, even in summer. Second, the upper intertidal zone is characterized by lower index values in winter and relatively high values in summer. This implies a predominantly seasonal control on the biofilm development in this zone. Third, in the lower supratidal zone, the index values are almost identical during both winter and summer. This implies non-seasonal biological effects in this zone. Concomitant empirical studies on the composition of microbial mats and films suggest that the dominant microbial type influences the MOD-I value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.1999.00218.x
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  • 2
    Electronic Resource
    Electronic Resource
    Interactions between nitrogen fixation and oxegenic photosynthesis in a marine cyanobacterial mat (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 7 (1990), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1990.tb01672.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of anoxia and high sulphide concentrations on heterotrophic microbial communities in reduced surface sediments (Black Spots) in sandy intertidal flats of the German Wadden Sea (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 44 (2003), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Black reduced sediment surfaces (Black Spots) in sandy intertidal flats of the German Wadden Sea (southern North Sea) are characterised by elevated sulphide concentrations (up to 20 mM) and low redox potentials. It is assumed that the appearance of Black Spots is linked to elevated levels of organic matter content within the sediments. In order to establish the effect of high substrate and sulphide concentrations on the heterotrophic microbial communities in Black Spot sediments, bacterial abundances and the potential C-source utilisation patterns of microbial communities were compared in natural and artificially induced Black Spots and unaffected control sites. Bacterial numbers were estimated by direct counts and the most probable number technique for different physiological groups, while patterns of C-substrate utilisation of entire aerobic microbial communities were assessed using the Biolog™ sole-carbon-source-catabolism assay. Bacterial abundances at Black Spot sites were increased, with increases in mean cell numbers, more disperse data distributions and more extreme values. Substrate utilisation patterns of aerobic microbial communities were significantly different in Black Spot sediment slurries, showing diminished richness (number of C-sources catabolised) and substrate diversity (Shannon diversity index) in comparison to unaffected sites. Principal component analysis clearly discriminated Black Spot utilisation patterns from controls and indicated that microbial communities in individual Black Spot sites are functionally diverse and differ from communities in oxidised surface sediments and reduced subsurface sediments at control sites. This work suggests that potentially negative effects on microbial communities in Black Spot sediments, through anoxia and high sulphide concentrations, are balanced by the stimulating influence of substrate availability, leading to comparable or higher bacterial numbers, but lower functional microbial diversity of aerobic microbial communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0168-6496(03)00076-X
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  • 4
    Electronic Resource
    Electronic Resource
    Methanogenesis in the hypersaline Solar Lake (Sinai) (1984)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 25 (1984), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Enrichment studies on microbial mat sediments (potential stromatolites) from the hypersaline Solar Lake (Sinai) indicated high numbers of methanogenic bacteria (up to 105 ml−1 sediment) in spite of the high sulfate reduction rate, sulfate concentration and salinity. Among H2/CO2, acetate and monomethylamine, the methylated amine was the preferred substrate. The predominant species enriched was a Methanosarcina sp. The findings indicate that methanogenic bacteria play an important role in hypersaline sulfate-enriched anoxic sediments and stromatolithic microbial mats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1984.tb01460.x
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  • 5
    Electronic Resource
    Electronic Resource
    Interactions between nitrogen fixation and oxegenic photosynthesis in a marine cyanobacterial mat (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 74 (1990), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb04052.x
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  • 6
    Electronic Resource
    Electronic Resource
    Methanogenesis in a saltern in the Bretagne (France) (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 62 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Salterns in the Bretagne (France), exhibiting different stages of salinity of 5% to 33% evolved up to 0.7 mmol methane per m2 per day. Methane concentrations of up to 0.4 mM were found. High methane evolution rates and increased methane concetration were restricted to basins of up to 7% and more than 15% salinity, and to the upper 10 cm of the sediments, where high sulfate concentrations (50 to 100 mM) occurred as well. Basins of 10–15% salinity exhibited only low methane evolution rates (less than 0.05 mmol methane per m2 per day) and low methane concentrations (less than 0.02 mM). Gas bubbles arising during times of increased photosynthetic activity from the microbial mats covering the sediments of the saltern basins contained up to 2% methane. Addition of methylated amines and methanol, but not of H2/CO2, formate or acetate, to sediments slurries from basins of up to 12% salinity resulted in a rapid enrichment of methanogenic populations. Enriched methanogenic bacteria did not grow at salinities exceeding 15% or temperatures exceeding 45°C, and showed characteristics similar to those documented for Methanococcus halophilus and strain SF1 (DSM 3243). No enrichments were obtained from basins of more than 20% salinity in spite of methane being produced and evolved from those basins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03688.x
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  • 7
    Electronic Resource
    Electronic Resource
    Microbial mats and physicochemistry in a saltern in the Bretagne (France) and in a laboratory scale saltern model (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 62 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A saltern near La Baule (Bretagne, France) was remodeled in a programmable temperature and humidity controlled walk-in environmental chamber resembling the characteristics of the original saltern. The saltern showed different types of microbial mats predominantly composed of algae, oxy- and anoxyphotobacteria, and associated chemoorganotrophic bacteria, fungi and animals. Well-developed microbial mats were found up to a salinity of 10% during the three or four months in summer when salinity gradients and NaCl precipitation were established. The main phototrophic organisms were diatoms, the cyanobacteria Aphanothece, Microcoleus, Spirulina, and Oscillatoria, and Chromatiaceae. At higher salinity, Halobacterium sp., diatoms, and Dunaliella were dominant. Typical microbial mats and saltern-typical invertebrate, algal and bacterial species also developed in the saltern model, building up a stable community. The ionic composition of the brines and physicochemical parameters were similar to those determined for the original saltern. Different photosynthetic organisms, e.g. a filamentous purple bacterium and a hypersaline Chloroflexus-like organism, could be enriched within the microbial mats by changing the light regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03689.x
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  • 8
    Electronic Resource
    Electronic Resource
    Structure and development of a benthic marine microbial mat (1985)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 31 (1985), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Vertically stratified microbial communities of phototrophic bacteria in the upper intertidal zones of the North Sea island of Mellum were investigated. Growth and population dynamics of the cyanobacterial mat were followed over three successive years. It was concluded that the initial colonization of the sandy sediments was by the cyanobacterium Oscillatoria. In well-established mats, however, the dominant organism was Microcoleus chthonoplastes. The observed succession of cyanobacteria during mat development is correlated with nitrogen fixation. Nitrogen fixation is necessary in this low-nutrient environment to ensure colonization by mat-constructing cyanobacteria. Under certain conditions, a red layer of purple sulfur bacteria developed underneath the cyanobacterial mat in which Chromatium and Thiocapsa spp. dominated, but Thiopedia and Ectothiorhodospira spp. have also been observed. Measurements of light penetrating the cyanobacterial mat indicated that sufficient light is available for the photosynthetic growth of purple sulfur bacteria. Profiles of oxygen, sulfide and redox potential within the microbial mat were measured using microelectrodes. Maximum oxygen concentrations, measured at a depth of 0.7 mm, reached levels more than twice the normal air saturation. Dissolved sulfide was not detected by the microelectrodes. Determination of acid-distilled sulfide, however, revealed appreciable amounts of bound sulfide in the mat. Redox profiles measured in the mat led to the conclusion that the upper 10 mm of the sedimentary sequence is in a relatively oxidized state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1985.tb01138.x
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  • 9
    Electronic Resource
    Electronic Resource
    Aerobic nitrogen fixation in pure cultures of a benthic marine Oscillatoria (cyanobacteria) (1981)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 11 (1981), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1981.tb06983.x
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  • 10
    Electronic Resource
    Electronic Resource
    Uranium mobilization from low-grade ore by cyanobacteria (1985)
    Springer
    Applied microbiology and biotechnology 21 (1985), S. 374-377 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Three cyanobacterial isolates (two LPP-B forms and one Anabaena or Nostoc species) from different environments could mobilize uranium from low-grade ores. After 80 days, up to 18% uranium had been extracted from coal and 51% from carbonate rock by the filamentous cyanobacterium OL3, a LPP-B form. Low growth requirements with regard to light and temperature optima make this strain a possible candidate for leaching neutral and alkaline low-grade uranium ores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249983
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