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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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Overview of the different levels of hierarchy encountered in magnetotactic bacteria with respect to their length scale. Level 1: electron tomography reconstruction of a MSR-1 magnetosome chain of about 1 µm length. Level 2: TEM image of an isolated MSR-1 magnetosome, the width of the image represents 50 nm. Level 3: two-dimensional diffractogram of whole cells AMB-1, the lattice parameter is optimized at a sub-nanometre scale. This final new level was identified in this study.
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RSIF20100576F5: Overview of the different levels of hierarchy encountered in magnetotactic bacteria with respect to their length scale. Level 1: electron tomography reconstruction of a MSR-1 magnetosome chain of about 1 µm length. Level 2: TEM image of an isolated MSR-1 magnetosome, the width of the image represents 50 nm. Level 3: two-dimensional diffractogram of whole cells AMB-1, the lattice parameter is optimized at a sub-nanometre scale. This final new level was identified in this study.

Mentions: We have studied the structure of magnetite nanoparticles from biogenic and abiotic origin by high-resolution XRD. We measured a significant difference in lattice parameter between the biological and the synthetic materials and between isolated and non-treated biological materials. We could show that this difference was associated with different oxidation state and particularly that the original and non-treated biogenic nanomagnetite is stoichiometric, i.e. structurally pure. We hypothesized that this can only be performed if the bacteria actively generate optimal physico-chemical conditions within their organelles. The cells are able to biomineralize stoichiometric magnetite at room temperature, whereas stoichiometric inorganic nanomagnetite is unstable when not protected from oxidation. Moreover, the difference observed between the biological and synthetic samples at room temperature of only 0.067 per cent in the lattice parameter depicts a change of 4.1 per cent in the respective magnetic moment. We thus speculated that the exceptional magnetic properties of the magnetotactic bacteria arose not only from the successive hierarchical level of magnetosome dimension and organization into chains but also from the atomic structure of the magnetic biological material (figure 5). This hierarchical structuring is a striking example of nature's ability of structure–function optimization. In addition, the difference in lattice parameter measured between isolated and non-treated biological materials might help explain controversial results of bulk magnetic studies that found anomalous behaviour for bacterial magnetosomes. We think that it would be of interest to apply such high-resolution XRD technique to study the magnetosomes doped with metals other than iron and other further genetic modification of the magnetosomes that might impact the biomineralization process. We believe that the study of the structural perfection of unique nanometre-scaled biological materials and the underlying mechanisms of their synthesis will aid in the design of advanced magnetic materials conceptually inspired by the natural system.Figure 5.


Structural purity of magnetite nanoparticles in magnetotactic bacteria.

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

Overview of the different levels of hierarchy encountered in magnetotactic bacteria with respect to their length scale. Level 1: electron tomography reconstruction of a MSR-1 magnetosome chain of about 1 µm length. Level 2: TEM image of an isolated MSR-1 magnetosome, the width of the image represents 50 nm. Level 3: two-dimensional diffractogram of whole cells AMB-1, the lattice parameter is optimized at a sub-nanometre scale. This final new level was identified in this study.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSIF20100576F5: Overview of the different levels of hierarchy encountered in magnetotactic bacteria with respect to their length scale. Level 1: electron tomography reconstruction of a MSR-1 magnetosome chain of about 1 µm length. Level 2: TEM image of an isolated MSR-1 magnetosome, the width of the image represents 50 nm. Level 3: two-dimensional diffractogram of whole cells AMB-1, the lattice parameter is optimized at a sub-nanometre scale. This final new level was identified in this study.
Mentions: We have studied the structure of magnetite nanoparticles from biogenic and abiotic origin by high-resolution XRD. We measured a significant difference in lattice parameter between the biological and the synthetic materials and between isolated and non-treated biological materials. We could show that this difference was associated with different oxidation state and particularly that the original and non-treated biogenic nanomagnetite is stoichiometric, i.e. structurally pure. We hypothesized that this can only be performed if the bacteria actively generate optimal physico-chemical conditions within their organelles. The cells are able to biomineralize stoichiometric magnetite at room temperature, whereas stoichiometric inorganic nanomagnetite is unstable when not protected from oxidation. Moreover, the difference observed between the biological and synthetic samples at room temperature of only 0.067 per cent in the lattice parameter depicts a change of 4.1 per cent in the respective magnetic moment. We thus speculated that the exceptional magnetic properties of the magnetotactic bacteria arose not only from the successive hierarchical level of magnetosome dimension and organization into chains but also from the atomic structure of the magnetic biological material (figure 5). This hierarchical structuring is a striking example of nature's ability of structure–function optimization. In addition, the difference in lattice parameter measured between isolated and non-treated biological materials might help explain controversial results of bulk magnetic studies that found anomalous behaviour for bacterial magnetosomes. We think that it would be of interest to apply such high-resolution XRD technique to study the magnetosomes doped with metals other than iron and other further genetic modification of the magnetosomes that might impact the biomineralization process. We believe that the study of the structural perfection of unique nanometre-scaled biological materials and the underlying mechanisms of their synthesis will aid in the design of advanced magnetic materials conceptually inspired by the natural system.Figure 5.

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