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  • Engineering  (9)
  • Escherichia coli
  • 1990-1994  (3)
  • 1985-1989  (7)
  • 1980-1984  (4)
  • 1930-1934
  • 1
    ISSN: 1432-072X
    Keywords: Iron-limitation ; Escherichia coli ; Respiratory chains ; Cytochromes ; Gallium ; Metal uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of iron limitation on growth, the composition and function of the respiratory chains, and gallium uptake inEscherichia coli have been studied. Decreasing the iron concentration in a defined medium using Chelex resin gave lower growth yields in both continuous culture and prolonged batch culture. In the former, ironlimited (entering [Fe]≤2.0 μM) cells exhibited diminished respiration rates, respiration-driven proton translocation quotients, and levels of non-haem iron and cytochromes. The cellular concentration of haemoproteinb-590 (a cytochromea 1-like hydroperoxidase) decreased 20-fold on iron limitation, whilst a CO-binding pigment with an absorption maximum in the dithionite-treated form near 500 nm appeared. Gallium(III) (9 μM) added to iron-limited, but not iron-sufficient, cultures diminished growth yields further; cells grown with low entering concentrations of iron took up less gallium than iron-sufficient cells. These results are attributed to the interference by gallium(III) with siderophore-mediated metal uptake. Gallium also stimulated iron uptake and was itself accumulated by iron-sufficient cells, suggesting that gallium(III) also affects the iron transport system(s) of low affinity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 156 (1991), S. 507-512 
    ISSN: 1432-072X
    Keywords: Aluminium and bacteria ; Metal speciation ; Iron transport ; Biosorption of metals ; Metal-microbe interactions ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The toxicity and binding of aluminium to Escherichia coli has been studied. Inhibition of growth by aluminium nitrate was markedly dependent on pH; growth in medium buffered to pH 5.4 was more sensitive to 0.9 mM or 2.25 mM aluminium than was growth at pH 6.6–6.8. In medium buffered with 2-(N-morpholino)ethanesulphonic acid (MES), aluminium toxicity was enhanced by omission of iron from the medium or by use of exponential phase starter cultures. Analysis of bound aluminium by atomic absorption spectroscopy showed that aluminium was bound intracellularly at one type of site with a K m of 0.4 mM and a capacity of 0.13 mol (g dry wt)-1. In contrast, binding of aluminium at the cell surface occurred at two or more sites with evidence of cooperativity. Addition of aluminium nitrate to a weakly buffered cell suspension caused acidification of the medium attributable to displacement of protons from cell surfaces by metal cations. It is concluded that aluminium toxicity is related to pH-dependent speciation [with Al(H2O) 6 3+ probably being the active species] and chelation of aluminium in the medium. Aluminium transport to intracellular binding sites may involve Fe(III) transport pathways.
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  • 3
    ISSN: 1432-072X
    Keywords: Cell division ; Escherichia coli ; Ruthenium compounds ; Filament formation ; Mutagenesis ; Cell cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dimeric, mixed-valence [(Ru(II), Ru(III)] compounds of ruthenium caused filament formation in growing cultures of Escherichia coli K12. Three compounds with the general formula Ru2(NH3)6X5 · H2O (where X is a halide) were tested; in order of decreasing effectiveness (and with the concentration giving maximum effect), these were the bromo (10-5 M), chloro (10-4 to 10-5 M), and iodo (10-3 to 10-4 M) analogues. Filamentation elicited by the bromo and chloro compounds was spontaneously reversible after 3–4 h, and tentatively attributed to oxidation of the active mixed-valence form to inactive Ru(III) complexes. Several compounds known to accelerate division of filaments formed under other conditions were ineffective in reversing the filamentation, but the presence of 0,43 M-dimethylsulphoxide totally inhibited filamentation caused by the bromo or chloro compounds and by cis-Pt(NH3)2Cl2 (cisplatin), an established filamenting and antitumour agent. The ruthenium complexes bound to mammalian DNA, but were without effect on the UV spectrum or cellular content of DNA in E. coli, despite showing marked mutagenic activity in reverse mutation tests with Salmonella typhimurium. Cells remained sensitive to inhibition of division by the ruthenium complexes until immediately prior to the division event. Possibilities for the (probably complex) mode of action and the potential of related compounds for therapeutic use are discussed.
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  • 4
    ISSN: 1432-072X
    Keywords: Copper-limitation ; Escherichia coli ; Cytochrome oxidases ; Oxygen reduction ; Respiratory chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role(s) of copper in a bacterial cytochrome oxidase of the aa 3-type was investigated by growth of Paracoccus denitrificans NCIB 8944, in batch and steady state continuous culture, in a medium from which the bulk of the copper had been extracted. In a medium containing approximately 0.02 μM copper, cellular copper content, cytochromes a+a 3 and cytochrome a 3 were reduced to 55%, 58% and 33% respectively of control values and there were also less marked decreases in cytochromes c+c 1 (to 85%) and a CO-binding b-type cytochrome, possibly cytochrome o (to 71%). Copper deficiency elicited in reduced minus oxidized difference spectra a shift to shorter wavelengths and narrowing of the band width of the α-band of the oxidase, and loss of a (negative) band near 830 nm attributable to CuA (the copper functionally associated with haem a in the oxidase complex). The oxidase in copper-deficient cells reacted with oxygen to form the oxy “Compound A” at rates similar to that in control cells but CO recombination to ferrous haem a 3 was slowed 4-fold in the copper deficient case. The results are interpreted as indicating loss of CuA and changes in the proportions of haems a and a 3 with retention of catalytic activity. Titrations of respiration rates with antimycin suggested that copper deficiency did not result in diversion of electron flux through an antimycin A-insensitive, cytochrome o-terminated branch of the respiratory chain.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 213 (1988), S. 99-104 
    ISSN: 1617-4623
    Keywords: Promoters ; Escherichia coli ; Proteus vulgaris ; Hemolysin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hemolytic activity of Escherichia coli and Proteus vulgaris is determined by common contiguous genes encoding synthesis (hly C, hly A) and specific secretion (hly B, hly D) of active hemolysin. Nevertheless, the hlyC-proximal DNA sequences directing production of the homologous hemolysins by the recombinant DNAs P. vulgaris pVU763-709 and E. coli pANN202-312 showed no extensive homology. Primer extension and S1 nuclease protection were used to define in the two sequences the 5′ termini of hly transcripts synthesized in vivo and thus to infer the active hly promoters sequences. The E. coli hly C upstream region contained three separate promotors directing in vivo hly transcription, while the corresponding transcription of the P. vulgaris hly operon originated from a single distinct promotor, the-35 and-10 sequences of which formed part of an inverted repeat sequence. Elevated hemolytic activity caused by upstream Tn5 insertions in pVU763-709 resulted from increased transcription from this promotor.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 21 (1985), S. 163-168 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A fully discrete stability and accuracy analysis of some algorithms for the one-dimensional heat equation is presented. Results illustrate that 2-pass explicit schemes which simultaneously employ lumped and coupled capacity matrices are capable of improved performance over the standard 1-pass explicit scheme.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 733-751 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A concise and efficient algorithm is presented for deriving finite element shape functions from an arbitrary set of independent functions. Based on special one-dimensional interpolatory schemes derived via the algorithm, a variety of two- and three-dimensional interpolatory schemes are developed which are useful for modelling singular behaviour. The methodology presented is general and may be fruitfully applied to the development of ‘special’ finite element shape functions for a variety of other situations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1413-1418 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new finite element procedure is introduced for the analysis of nearly-incompressible media. The approach may be simply implemented by a small change of the standard technique, and is applicable to arbitrary anisotropic and/or nonlinear media. The procedure is shown to specialize to the selective integration and mean-dilatation formulations under appropriate hypothesis.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1862-1867 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An improved algorithm is presented for integrating rate constitutive equations in large-deformation analysis. The algorithm is shown to be ‘objective’ with respect to large rotation increments.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 1485-1485 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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