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Structural purity of magnetite nanoparticles in magnetotactic bacteria.

Fischer A, Schmitz M, Aichmayer B, Fratzl P, Faivre D - J R Soc Interface (2011)

Bottom Line: However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified.Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones.Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, , Science Park Golm, 14424 Potsdam, Germany.

ABSTRACT
Magnetosome biomineralization and chain formation in magnetotactic bacteria are two processes that are highly controlled at the cellular level in order to form cellular magnetic dipoles. However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified. For the first time, the microstructure of intracellular magnetosomes was investigated using high-resolution synchrotron X-ray diffraction. Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones. Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized. The hierarchical structuring of the magnetosome chain thus starts with the formation of structurally pure magnetite nanoparticles that in turn might influence the magnetic property of the magnetosome chains.

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(a) Two-dimensional and one-dimensional XRD pattern of the biogenic AMB-1 sample with NIST standard. Only the peaks used for data analysis are indexed. (b) Integrated one-dimensional X-ray diffractograms for all measured samples. All indexed diffraction peaks correspond to magnetite (or maghemite), while the remaining diffraction peaks belong to the α-quartz standard peaks. The (311) MGT (MGH) and (101) α-quartz peak are highlighted (boxes). (c) Enlargement of the (101) α-quartz diffraction peak and of the (311) diffraction peak of MGT. Depicted are MGT in whole cells of strains AMB-1 (green), MSR-1 (red) and ΔmamGFDC (blue), isolated (turquoise) and treated (rose) magnetosomes, and reference synthetic MGT (black) and MGH (brown).
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RSIF20100576F2: (a) Two-dimensional and one-dimensional XRD pattern of the biogenic AMB-1 sample with NIST standard. Only the peaks used for data analysis are indexed. (b) Integrated one-dimensional X-ray diffractograms for all measured samples. All indexed diffraction peaks correspond to magnetite (or maghemite), while the remaining diffraction peaks belong to the α-quartz standard peaks. The (311) MGT (MGH) and (101) α-quartz peak are highlighted (boxes). (c) Enlargement of the (101) α-quartz diffraction peak and of the (311) diffraction peak of MGT. Depicted are MGT in whole cells of strains AMB-1 (green), MSR-1 (red) and ΔmamGFDC (blue), isolated (turquoise) and treated (rose) magnetosomes, and reference synthetic MGT (black) and MGH (brown).

Mentions: Typical transmission electron microscopy (TEM) images of the different strains of magnetotactic bacteria and the associated crystal size distribution are shown in figure 1. A two-dimensional diffraction pattern with the corresponding one-dimensional diffractogram obtained for the AMB-1 sample is shown in figure 2a. One-dimensional diffractograms of all samples are shown in figure 2b with an enlargement in figure 2c of the most intense (311) and (101) reflections of, respectively, magnetite/maghemite and α-quartz, the latter being used as internal standard (supporting info). For all samples, the diffraction patterns could be indexed according to magnetite (respectively, maghemite), cubic unit cell (space group Fd3m). The lattice parameter, a, was calculated by fitting the angular positions of the measured Bragg peaks. The a-values, extracted from individual diffraction peak positions, as well as the averaged lattice parameter aa are summarized in table 1 and figure 3.Figure 1.


Structural purity of magnetite nanoparticles in magnetotactic bacteria.

Fischer A, Schmitz M, Aichmayer B, Fratzl P, Faivre D - J R Soc Interface (2011)

(a) Two-dimensional and one-dimensional XRD pattern of the biogenic AMB-1 sample with NIST standard. Only the peaks used for data analysis are indexed. (b) Integrated one-dimensional X-ray diffractograms for all measured samples. All indexed diffraction peaks correspond to magnetite (or maghemite), while the remaining diffraction peaks belong to the α-quartz standard peaks. The (311) MGT (MGH) and (101) α-quartz peak are highlighted (boxes). (c) Enlargement of the (101) α-quartz diffraction peak and of the (311) diffraction peak of MGT. Depicted are MGT in whole cells of strains AMB-1 (green), MSR-1 (red) and ΔmamGFDC (blue), isolated (turquoise) and treated (rose) magnetosomes, and reference synthetic MGT (black) and MGH (brown).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104334&req=5

RSIF20100576F2: (a) Two-dimensional and one-dimensional XRD pattern of the biogenic AMB-1 sample with NIST standard. Only the peaks used for data analysis are indexed. (b) Integrated one-dimensional X-ray diffractograms for all measured samples. All indexed diffraction peaks correspond to magnetite (or maghemite), while the remaining diffraction peaks belong to the α-quartz standard peaks. The (311) MGT (MGH) and (101) α-quartz peak are highlighted (boxes). (c) Enlargement of the (101) α-quartz diffraction peak and of the (311) diffraction peak of MGT. Depicted are MGT in whole cells of strains AMB-1 (green), MSR-1 (red) and ΔmamGFDC (blue), isolated (turquoise) and treated (rose) magnetosomes, and reference synthetic MGT (black) and MGH (brown).
Mentions: Typical transmission electron microscopy (TEM) images of the different strains of magnetotactic bacteria and the associated crystal size distribution are shown in figure 1. A two-dimensional diffraction pattern with the corresponding one-dimensional diffractogram obtained for the AMB-1 sample is shown in figure 2a. One-dimensional diffractograms of all samples are shown in figure 2b with an enlargement in figure 2c of the most intense (311) and (101) reflections of, respectively, magnetite/maghemite and α-quartz, the latter being used as internal standard (supporting info). For all samples, the diffraction patterns could be indexed according to magnetite (respectively, maghemite), cubic unit cell (space group Fd3m). The lattice parameter, a, was calculated by fitting the angular positions of the measured Bragg peaks. The a-values, extracted from individual diffraction peak positions, as well as the averaged lattice parameter aa are summarized in table 1 and figure 3.Figure 1.

Bottom Line: However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified.Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones.Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, , Science Park Golm, 14424 Potsdam, Germany.

ABSTRACT
Magnetosome biomineralization and chain formation in magnetotactic bacteria are two processes that are highly controlled at the cellular level in order to form cellular magnetic dipoles. However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified. For the first time, the microstructure of intracellular magnetosomes was investigated using high-resolution synchrotron X-ray diffraction. Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones. Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized. The hierarchical structuring of the magnetosome chain thus starts with the formation of structurally pure magnetite nanoparticles that in turn might influence the magnetic property of the magnetosome chains.

Show MeSH
Related in: MedlinePlus