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  • 1
    Electronic Resource
    Electronic Resource
    Cloning and expression of a Nostoc sp. leucine biosynthetic gene in Escherichia coli (1986)
    Springer
    Archives of microbiology 145 (1986), S. 315-321 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; DNA restriction and cloning ; Gene fusions ; Leucine biosynthesis ; Mutant complementation ; Nostoc ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genomic DNA extracted from the symbiotically-competent, heterocyst-forming cyanobacterium Nostoc sp. strain 7801 was resistant to cleavage by a number of restriction endonucleases. A cosmid library of Nostoc DNA was prepared and maintained in the modification-limited Escherichia coli strain HB101. Analysis of cloned Nostoc DNA fragments indicated infrequent occurrence of restriction endonuclease recognition sites in the Nostoc genome. The Nostoc genomic library was screened for sequences complementing mutations in the E. coli leucine and proline biosynthetic operons. Two cosmids complementing leuB were isolated but none for leuA, leuC, leuD, or proA were detected in 1000 cosmids. A 3.0 kb fragment subcloned from one of the cosmids complemented mutations in leuB when inserted into the HindIII site of pBR322 in either orientation, demonstrating that transcription of leuB originated within the cloned fragment. The cloned fragment also carries a second site capable of initiating transcription of fused antibiotic resistance genes. While transcription of Nostoc DNA sequences did occur in E. coli, unknown barriers must also exist that prevented additional biological complementation of specific E. coli mutations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00470864
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Redox processes in recent sediments of the river Meuse, The Netherlands (2000)
    Springer
    Biogeochemistry 48 (2000), S. 217-235 
    Details
    ISSN: 1573-515X
    Keywords: diagenesis ; modelling ; organic matter ; pore water ; redox ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Pore-water concentrations of inorganic solutes were measured at four locations in a recent sedimentation area of the river Meuse in The Netherlands. The pore-water concentration profiles were interpreted using the steady state one-dimensional reaction/transport model STEADYSED1. This model explicitly accounts for the organic matter degradation pathways and secondary redox reactions. Results show that the model reproduces the measured pore-water profiles of redox species reasonably well, although significant divergence is observed for pH. The latter is due to the absence of pH buffering by CaCO3 in the model. At all locations, methanogenesis is the major pathway of organic matter degradation below 3 cm from the sediment-water interface. However, organic matter degradation rates by methanogenesis may be overestimated, because methane ebullition is not included. Differences in profiles of redox-sensitive ions among the four locations are explained by differences in depositional conditions, in particular the sediment accumulation rate and supply of organic matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006268325889
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Mobilisation of Heavy Metals in Contaminated Sediments in the River Meuse, The Netherlands (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 567-586 
    Details
    ISSN: 1573-2932
    Keywords: Complexation ; diffusion ; heavymetals ; mobilisation ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Due to seasonal variation in bottom-water temperature and degradation of organic matter, the depths of the redox boundaries fluctuate in sediments of the river Meuse. This is reflected by a non-steady state behaviour of heavy metals in the surface sediments. Levels of acid-volatile sulphides suggest that dissolved concentrations of heavy metals in the anoxic pore waters are determined by their respective sulphide phases. However, complexation with dissolved organic ligands may significantly increase dissolved concentrations of heavy metals. In most sediments studied, a distinct peak in dissolved concentrations of heavy metals is measured immediately below the sediment-water interface. This concentration peak may be attributed to degradation of organic matter and oxidation of sulphides. Dissolved concentration gradients indicate that upward diffusion of heavy metals from the sediment can contribute to concentrations in the surface water, although significant effects may be confined to specific locations. In addition, it is shown that release of heavy metals as dissolved species to the surface water is negligible compared to particulate-bound fluxes of heavy metals to the sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005146927718
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Isolation and characterization of Anacystis nidulans R2 mutants affected in nitrate assimilation: Establishment of two new mutant types (1988)
    Springer
    Molecular genetics and genomics 213 (1988), S. 223-228 
    Details
    ISSN: 1617-4623
    Keywords: Cyanobacteria ; Nitrate reductase mutants ; Nitrite reductase mutants ; Regulatory mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Eighteen mutant strains of the unicellular cyanobacterium Anacystis nidulans R2 that are unable to assimilate nitrate have been isolated after transposon Tn901 mutagenesis. Characterization of phenotypes and transformation tests have allowed the distinction of five different mutant types. The mutants exhibiting a nitrate reductase-less phenotype were identified as being affected in previously defined loci, as they could be transformed to the wild type by one of the plasmids pNR12, pNR63 or pNR193, which contain cloned genes of A. nidulans R2 involved in nitrate reduction. The mutations in strains FM2 and FM16 appear to affect two other genes involved in nitrate assimilation. Strain FM2 apparently bears a single mutation which results in both lack of nitrite reductase activity and loss of ammonium-promoted repression of nitrate reductase synthesis. FM16 has a low but significant level of nitrate reductase that is also freed from repression by ammonium, and an increased level of nitrite reductase activity. FM16 exhibited properties which indicate that this mutant strain might also be affected in the transport of nitrate into the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339585
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    Paper (German National Licenses)
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