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Small-angle neutron scattering from bacterial magnetite (1990)

Krueger, S. ; Olson, G. J. ; Rhyne, J. J. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 67 (1990), S. 4475-4477

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Small-angle neutron scattering was used to study the magnetic properties of intracellular magnetite crystals (magnetosomes) in the bacterium, Aquaspirillum magnetotacticum, grown in pure culture. An average of 20 single-domain magnetite (Fe3O4) particles of diameter 400–500 A(ring) are arranged in a chain that longitudinally traverses each cell. The net magnetic dipole moment carried by each chain is sufficient to orient the bacterium in the geomagnetic field. A contrast variation series, performed on a nonmagnetic variant, established that a 30% D2O/H2O ratio in the suspension buffer resulted in the minimization of the scattering from the bacterium itself, thereby enhancing that from the magnetosomes. Measurements of A. magnetotacticum in 30% D2O and an applied field of 25 G confirmed that the scattering from the magnetite particles in bacteria grown under iron-rich conditions is of ferromagnetic character, while that from magnetosomes in bacteria grown under iron-starved conditions is characteristic of superparamagnetic particles. In both cases, the wave-vector dependence of the scattering can be represented by a sum of Lorentzian plus Lorentzian squared terms, from which longitudinal as well as transverse spin correlation lengths were extracted. The results describe dynamic spin correlation lengths on the order of 50 A(ring), which are superposed on the static magnetosome cluster.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.344886

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Geobacter metallireducens gen. nov. sp. nov., a microorganism capable of coupling the complete oxidation of organic compounds to the reduction of iron and other metals (1993)

Lovley, D. R. ; Giovannoni, S. J. ; White, D. C. ; [et al.]

Springer

Archives of microbiology 159 (1993), S. 336-344

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ISSN: 1432-072X

Keywords: Iron ; Uranium ; Manganese ; Nitrate ; Anaerobic sediments ; Delta proteobacteria ; Aromatics ; Heavy metals

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further characterized. This strict anaerobe oxidizes several short-chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the sole electron acceptor. Furthermore, acetate is also oxidized with the reduction of Mn (IV), U (VI), and nitrate. In whole cell suspensions, the c-type cytochrome(s) of this organism was oxidized by physiological electron acceptors and also by gold, silver, mercury, and chromate. Menaquinone was recovered in concentrations comparable to those previously found in gram-negative sulfate reducers. Profiles of the phospholipid ester-linked fatty acids indicated that both the anaerobic desaturase and the branched pathways for fatty acid biosynthesis were operative. The organism contained three lipopolysaccharide hydroxy fatty acids which have not been previously reported in microorganisms, but have been observed in anaerobic freshwater sediments. The 16S rRNA sequence indicated that this organism belongs in the delta proteobacteria. Its closest known relative is Desulfuromonas acetoxidans. The name Geobacter metallireducens is proposed.