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  • 1
    Electronic Resource
    Electronic Resource
    An amino-terminal domain of Enterococcus faecalis aggregation substance is required for aggregation, bacterial internalization by epithelial cells and binding to lipoteichoic acid (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 52 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Aggregation substance (AS), a plasmid-encoded surface protein of Enterococcus faecalis, plays important roles in virulence and antibiotic resistance transfer. Previous studies have suggested that AS-mediated aggregation of enterococcal cells could involve the binding of this protein to cell wall lipoteichoic acid (LTA). Here, a method to purify an undegraded form of Asc10, the AS of the plasmid pCF10, is described. Using this purified protein, direct binding of Asc10 to purified E. faecalis LTA was demonstrated. Equivalent binding of Asc10 to LTA purified from INY3000, an E. faecalis strain that is incapable of aggregation, was also observed. Surprisingly, mutations in a previously identified aggregation domain from amino acids 473 to 683 that abolished aggregation had no effect on LTA binding. In frame deletion analysis of Asc10 was used to identify a second aggregation domain located in the N-terminus of the protein from amino acids 156 to 358. A purified Asc10 mutant protein lacking this domain showed reduced LTA binding, while a purified N-terminal fragment from amino acids 44–331 had high LTA binding. Like the previously described aggregation domain, the newly identified Asc10(156−358) aggregation domain was also required for efficient internalization of E. faecalis into HT-29 enterocytes. Thus, Asc10 possess two distinct domains required for aggregation and eukaryotic cell internalization: an N-terminal domain that promotes binding to LTA and a second domain located near the middle of the protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04045.x
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  • 2
    Electronic Resource
    Electronic Resource
    Inability of debilitated Escherichia coli χ 1776 to colonise germ-free rodents (1978)
    [s.l.] : Nature Publishing Group
    Nature 274 (1978), S. 397-398 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To assess the ability of #1776 to survive in fresh fecal samples and to obtain an indication of the sensitivity of our assay techniques, the following experiment was performed. Germ-free colon contents (2g) were mixed with 2 ml of a broth culture of #1776; after 1 h of incubation at 37 C, the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/274397a0
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid accumulation and turnover of soil carbon in a re-establishing forest (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 400 (1999), S. 56-58 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Present understanding of the global carbon cycle is limited by uncertainty over soil-carbon dynamics,,,,,. The clearing of the world's forests, mainly for agricultural uses, releases large amounts of carbon to the atmosphere (up to 〉2× 1015 g yr−1), ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/21867
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  • 4
    Electronic Resource
    Electronic Resource
    Nitrogen mineralization in high elevation forests of the Appalachians. I. Regional patterns in southern spruce-fir forests (1989)
    Springer
    Biodegradation 7 (1989), S. 131-145 
    Details
    ISSN: 1572-9729
    Keywords: Picea rubens ; Abies fraseri ; acid deposition ; forest decline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Annual and seasonal rates of net nitrogen mineralization were determined for 19 sites in the spruce-fir forests of the Southern Appalachian Mountains. These sites included high and low elevation stands of red spruce (Picea rubens Sarg.) and Fraser fir (Abies fraseri (Pursh.) Poir.) on east and west exposures on Whitetop Mountain, Virginia; Mt. Mitchell, North Carolina; and Clingman's Dome in the Great Smoky Mountains National Park. Mineralization rates were determined using in situ soil incubations in PVC tubes with ion exchange resin bags placed in the bottom of the tubes to collect leachate. Throughfall was collected in resin bags placed in the top of the tubes. Average initial NH4-N + NO3-N ranged from 0.6 to 4.8 kg N/ha across all plots, and average mineralization rates ranged from 26 to 180 kg-N ha−1 yr−1. Throughfall ranged from 18 to 32 kg-N ha−1 yr−1 with NH4-N accounting for about two-thirds of the throughfall N across all sites. Throughfall and mineralization rates were not related to elevation or exposure. The high rates of N mineralization and relatively high nitrate concentrations indicate that leaching losses of nitrogen and associated cations could be substantial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00004125
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  • 5
    Electronic Resource
    Electronic Resource
    An empirical analysis of the factors contributing to 20-year decrease in soil pH in an old-field plantation of loblolly pine (1989)
    Springer
    Biogeochemistry 8 (1989), S. 39-54 
    Details
    ISSN: 1573-515X
    Keywords: acid deposition ; forest decline ; soil acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The pH of weak-acid solutions is controlled by acid concentration (HA + A−), the degree of acid dissociation (A−/HA), and the strength of the acids present (pKa). We developed an empirical approach that allows the relative importance of each of these factors to be estimated for soils. This empirical model was applied to soils collected from an old-field plantation of loblolly pine (Pinus taeda L.) at 5 and 25 years of age. During this period, soil pH dropped by 0.3 to 0.8 units, and extractable calcium, magnesium and potassium declined by 20 to 80%. The empirical model indicates that the decline in pH resulted largely from the reduction in base saturation of the exchange complex. However, the average acid strength of the exchange complex decreased during the 20 years, preventing a greater decline of perhaps 0.1 to 0.2 units in the observed pH. The rate of decrease in the acid neutralizing capacity to pH 3.5 was about 1.3 kmolc/ha annually, while the increase in base neutralizing capacity was about 2.7 and 1.6 kmolc/ha annually to pH 5.5 and 8.2, respectively. Extractable alkali and alkaline earth cations declined by about 2.2 kmolc/ha annually, matched by the rate of increase in aluminium. These changes demonstrated the dynamic nature of poorly buffered soils, and indicated that changes in soil acidity may be expected over a period of decades (especially following changes in land-use).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02180166
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