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  • 11
    ISSN: 1432-072X
    Keywords: Key wordsZymomonas mobilis ; Metabolic flux ; analysis ; Sugar phosphates ; Glucose ; Fructose ; Xylose ; 13C-NMR ; In vivo 31P-NMR ; Rate-limiting step
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reasons for the well-known significantly different behaviour of the anaerobic, gram-negative, ethanologenic bacterium Zymomonas mobilis during growth on fructose (i.e. decreased growth and ethanol yields, increased by-product formation) as compared to that on its second natural substrate, glucose, have remained unexplained. A xylose-fermenting recombinant strain of Z. mobilis that was recently constructed in our laboratory also unexpectedly displayed an increased formation of by-products and a strongly reduced growth rate as compared to the parent strain. Therefore, a comprehensive study employing recently developed NMR-based methods for the in vivo analysis of intracellular phosphorylated pool sizes and metabolic fluxes was undertaken to enable a global characterization of the intracellular metabolic state of Z. mobilis during growth on 13C-labelled glucose, fructose and xylose in defined continuous cultures. The 13C-NMR flux analysis indicated that ribose 5-phosphate is synthesized via the nonoxidative pentose phosphate pathway in Z. mobilis, and it identified a metabolic bottleneck in the recombinant xylose-fermenting Z. mobilis strain at the level of heterologous xylulokinase. The 31P-NMR analyses revealed a global alteration of the levels of intracellular phosphorylated metabolites during growth on fructose as compared to that on glucose. The results suggest that this is primarily caused by an elevated concentration of intracellular fructose 6-phosphate.
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  • 12
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Assessment of trace element behavior in a series of six clear-water acidic lakes in northwestern New Jersey indicated that, while there was considerable variation over time, in general, the most acidic lakes exhibited the highest water column concentrations of aluminum (Al), cadmium (Cd), lead (Pb) and zinc (Zn). Concentrations of Cd and Zn in the upper 2.5 cm of sediment from two of the most acidic sites were markedly lower than those from other lakes. Submerged species of aquatic macrophytes generally contained higher trace element levels than did floating-leafed species. Concentrations of Al and Pb were highest in specimens growing in the most acidic lakes. Pb:Zn ratios varied dramatically, with Pb levels greatly exceeding those of Zn in several species of macrophytes in highly acidic Long Pine Pond and Crater Lake.
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  • 13
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The community structure of a benthic macroinvertebrate assemblage in a contaminated salt marsh was evaluated as part of an ecological characterization of a former chloralkali production facility in Georgia. Sample locations were chosen based on a gradient of the primary contaminants of concern, total mercury and polychlorinated biphenyls (PCBs), primarily Aroclor 1268. Sediment concentrations of Aroclor 1268 ranged from 2.3 to 150 mg/kg dry weight, while mercury concentrations ranged from 15 to 170 mg/kg dry weight in the study area. Mercury and PCBs were determined to be co-located in the sediments. Total organic carbon composition of the sediments was negatively associated with PCB and mercury concentrations. A total of 29 benthic taxa was identified in 49 samples; replicate samples were taken at each of five sampling locations. Mean infaunal density across all sampling locations was estimated at approximately 61,000 to 234,000 organisms m−2. Overall, polychaetes comprised 57% of the infaunal community with Manayunkia aestuarina as the dominant species. Oligochaetes, nematodes, crustacea, insects, and gastropods comprised 23.0, 18.0, 1.0, 0.7, and 0.2% of the overall benthic community, respectively. Density estimates of individual species between sampling locations showed no consistent patterns in response to pollutants. However, an analysis of higher taxonomic levels revealed some general trends. In uncontaminated areas, the benthic community was dominated by nematodes and oligochaetes, whereas moderate to highly contaminated areas were dominated by polychaetes and a smaller percentage of oligochaetes and nematodes. A trophic analysis of the same data set revealed that the community shifted from an evenly distributed percentage of surface and subsurface feeders in the uncontaminated areas to a community dominated by surface feeders in the more contaminated locations. Carnivores comprised from 0.13 to 0.90% of the trophic structure, with the percentage of carnivores generally decreasing with increasing contamination. Mercury and PCBs were bioaccumulating in representative marsh benthic invertebrates, presenting a potential source of contaminants to marsh consumers. Tissue PCB and tissue mercury concentrations were positively related to sediment PCB and mercury concentrations, respectively. A standard 14-day toxicity test using the amphipod Leptocheirus plumulosus showed no acute toxicity across the sampling locations.
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  • 14
    ISSN: 1433-8491
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 15
    ISSN: 1617-4623
    Keywords: sor genes ; l-sorbose ; Chromosomal rearrangement ; Klebsiella pneumoniae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A series of mutants was isolated in Klebsiella pneumoniae strain 1033, among them mutants unable to grown on l-sorbose. Different R' plasmids carrying the sor genes and other surrounding chromosomal genes were also isolated. Each plasmid contained the structural genes sorA for an Enzyme II of the phosphoenolpyruvate-dependent carbohydrate: phosphotransferase system, sorD for a d-glucitol 6-phosphate dehydrogenase, sorE for an l-sorbose 1-phosphate reductase, and the corresponding regulator gene sorR. These structural genes are coordinately expressed and inducible by l-sorbose. Cis-dominant and pleiotropic mutations rendering the expression of the sor genes constitutive or eliminating it were isolated. Complementation of a series of mutations in Escherichia coli K12 and K. pneumoniae by various R' and F' plasmids and by P1 transduction in K. pneumoniae located the sor genes within the following gene sequence: rbs rha pfkA metB ppc argH ilv btuB rpoB metA ace sor pgi malB uvrA. The rbs-ilv gene loci tightly linked in E. coli K12 at 84 min, are separated in the map of K. pneumoniae 1033 and located at 86 and 89 min, respectively.
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  • 16
    ISSN: 1617-4623
    Keywords: Klebsiella pneumoniae ; λplac-Mu hybrids ; LacZ fusions ; Hfr strains ; Conjugation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Klebsiella pneumoniae 1033-5P14 and its P1-sensitive derivative KAY2026 were found to be resistant to λ although they contained a LamB protein, active as a maltoporin. Sensitive derivatives could only be obtained after introduction of the pTROY9 plasmid which expresses lamB and the corresponding λ receptor from Escherichia coli K12 at high levels. Lysogenic derivatives from such strains were shown to carry the phage at secondary att sites and to give high titer lysates when induced. The use of λplac-Mu hybrid phages allowed the isolation from several operons of lacZ fusions orientated in, or against, the direction of transcription. Such insertions could subsequently be used to isolate stable Hfr strains by allowing homologous recombination to take place between the lac genes in the inserted hybrid phages and those of plasmid F′ts114 lac+ zzf20::Tn10. The Hfr strains were able to transfer K. pneumoniae chromosomal genes and allowed the mapping of such genes. Characteristic differences between this conjugation system and that of Escherichia coli K12 are discussed. The insertions also allowed determination of the direction of transcription of the gut gene, the newly mapped scr gene and of the sor gene cluster encoding enzymes for the metabolism of d-glucitol, sucrose and l-sorbose.
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  • 17
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 338 (1989), S. 478-483 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The maternal gene torso, required for determination of anterior and posterior terminal structures in the Drosophila embryo, was cloned using P-element tagging. Genetic evidence suggests that the action of the gene product is spatially restricted to the terminal regions; the torso messenger RNA, ...
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  • 18
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A methanogen-specific nested PCR approach was used to detect methanogenic archaea in seawater particles of the North Sea and the feces and the digestive tract of flounder (Platichthys flesus), a fish found in the North Sea. A number of 16S rDNA sequences with 97.6–99.5% similarity to Methanococcoides methylutens were found in the seawater particles as well as the digestive tract and fecal samples.
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  • 19
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A few genera of angiosperms are known as ‘resurrection plants’ since their leaves withstand complete desiccation. In many organisms, including some resurrection plants, desiccation tolerance is associated with the accumulation of special carbohydrates. We examined whether this is also true for the two European angiosperm genera of resurrection plants, Ramonda and Haberlea in the Gesneriaceae. Using gas chromatography, non-structural carbohydrates were determined as a percentage of the dry weight in leaves of Ramonda nathaliae subjected to various desiccation regimes. Sucrose was the predominant soluble carbohydrate in all samples, and its level steadily increased from 2 to 10% during desiccation. Starch amounted to ca 2% in control leaves and disappeared completely within 8 days of desiccation. Considerable amounts (1–2.5%) of raffinose and smaller amounts of its precursor galactinol (1-a-galactosyl-myo-inositol) were present in control leaves; these carbohydrates showed only minor changes upon desiccation. Similar results were obtained when excised leaves of Ramonda nathaliae, Ramonda myconi and Haberlea rhodopensis were subjected to desiccation. These data indicate that sucrose accumulation is connected to desiccation tolerance in Gesneriaceae; the presence of raffinose may be a pre-adaptation since this sugar prevents crystallization of sucrose during drying.
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  • 20
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The bactericidal antibiotic nalidixic acid can be used to select in cultures of Klebsiella pneumoniae and other penicillin-resistant enteric bacteria any auxotrophic and carbohydrate-negative mutant. Nalidixic acid treatment is superior to penicillin or d-cycloserine treatment, since no cross-feeding by lysed cells is possible, and it is simple to handle.
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