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  • 1
    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.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 323-328 
    ISSN: 1476-5535
    Keywords: Chromate, reduction of by bacteria ; Reduction of chromate by bacteria ; Bacterial reduction of chromate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Chromate-reducing bacteria were isolated from the cooling water of an electricity generating station where reduction of chromate had caused blockage of pipes by precipitation of chromium(III) oxide. Isolates identified included the generaAlcaligenes, Vibrio, Bacillus, Micrococcus, Staphylococcus andCorynebacterium. Isolate VMC-2 with the highest chromate-reducing activity was tentatively identified asComanonas testosteroni. The concentration of added chromate (K2CrO4, 20 μM)_decreased by 95% during 45 min incubation with whole cells of VMC-2. In comparison, two Fe(III)-reducing isolates,Vibrio metschnikovii andAeromonas hydrophila, from lake sediments, showed similarly high chromate-reducing activities, and were able to reduce 99% of added chromate (20 μM) in 45 min. Moderate Cr(VI)-reducers included strains ofBacillus, Vibrio andCorynebacterium. Micrococcus andStaphylococcus did not reduce Cr(VI). Sulfate (0.5 and 1.0 mM) inhibited the reduction of chromate by VMC-2 suggesting competition between the two oxyanions. Chromate-reducing activity was located in the soluble fraction of this isolate. The intermediacy of Cr(V)_in the reduction of chromate was confirmed by EPR spectroscopy. The bactericidal activity of hypochlorite towards isolate VMC-2 was determined.
    Type of Medium: Electronic Resource
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