Magnetosome formation in prokaryotes

Bazylinski, Dennis A.; Frankel, Richard B.

doi:10.1038/nrmicro842

Cited by 1,048 publications

(1,074 citation statements)

References 129 publications

Supporting

Mentioning

1,059

Contrasting

Unclassified

Order By: Relevance

“…All in-vitro experiments were carried out at 37 C in an incubator with 5% of CO2. Cell viability was evaluated using the so-called microculture tetrazolium assay (MTT), (15). This technique measures the ability of mitochondrial enzymes to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (purchased from Sigma, St Louis, MO, USA) into purple formazan crystals.…”

Section: In-vitro Heating Experiments Of the Various Types Of Nanoparmentioning

confidence: 99%

Chains of Magnetosomes Extracted from AMB-1 Magnetotactic Bacteria for Application in Alternative Magnetic Field Cancer Therapy

et al. 2011

View full text Add to dashboard Cite

International audienceChains of magnetosomes extracted from magnetotactic bacteria are shown to be highly efficient for alternative magnetic field cancer therapy. The viability of MDA-MB-231 breast cancer cells is relatively unaffected by the presence of less than ∼ 1 mg of chains of magnetosomes. When these cells are exposed to an oscillating magnetic field of frequency 183 kHz and field strengths of 20 to 60 mT, up to 100 % of them are destroyed. We show that it is possible to fully eradicate a tumor xeno-greffed on a mouse by administering a suspension containing ∼ 1 mg of chains of magnetosomes within the tumor and by exposing the mouse to three heat cycles of 20 minutes, during which the tumor temperature is raised to ∼ 43°C. We demonstrate the higher efficiency of the chains of magnetosomes compared with various other materials, i. e. whole inactive magnetotactic bacteria, individual magnetosomes not organized in chains and two different types of chemically synthesized nanoparticles currently tested for alternative magnetic field cancer therapy. The efficiency of the chains of magnetosomes is attributed to three factors, (i), a high magnetosome specific absorption rate (SAR), (ii), a homogenous distribution of the chains of magnetosomes within the tumor yielding uniform heating and (iii), the faculty of the chains of magnetosomes to penetrate within the cancer cells following the application of the alternative magnetic field, which enables intra-cellular heating. Biodistribution studies reveal that chains of magnetosomes administered directly within xeno-greffed breast tumors progressively leave the tumors during the 14 days following their administration and are then eliminated in the feces

show abstract

Section: In-vitro Heating Experiments Of the Various Types Of Nanoparmentioning

confidence: 99%

Chains of Magnetosomes Extracted from AMB-1 Magnetotactic Bacteria for Application in Alternative Magnetic Field Cancer Therapy

et al. 2011

View full text Add to dashboard Cite

show abstract

“…8−10 For instance, magnetotactic bacteria, a diverse family of aquatic prokaryotes, have the particular ability to align with the geomagnetic field due to the presence of the magnetosome, an organelle made of a lipid vesicle, in which biomineralized magnetite (Fe 3 O 4 ) or greigite (Fe 3 S 4 ) crystals of uniform sizes and well-defined shapes are embedded. 11 Therefore, they have been employed as effective tools to study biomineralization of magnetic crystals. 12−14 Mms6, one of several proteins tightly bound to the magnetosome magnetite crystal in magnetotactic bacteria Magnetospirillum magneticum AMB-1, has been implicated in the biomineralization of magnetite.…”

Section: ■ Introductionmentioning

confidence: 99%

Morphological Transformations in the Magnetite Biomineralizing Protein Mms6 in Iron Solutions: A Small-Angle X-ray Scattering Study

et al. 2015

View full text Add to dashboard Cite

Magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing residues in the Cterminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core-corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, plateletlike structures. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular threedimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing residues in the C-terminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core−corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, platelet-like structures.

show abstract

“…17 Since then, various properties of different magnetotactic bacteria have been extensively studied. [18][19][20][21][22][23][24][25][26][27][28][29][30][31] Most of the studies were performed on the bacteria extracted from natural aquatic habitats. Recently, significant progress was achieved in vitro studying the synthesis of magnetite by various bacterial strains.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, significant progress was achieved in vitro studying the synthesis of magnetite by various bacterial strains. 22 This allowed for the targeted modification of magnetic properties and various postsynthesis modifications. For reviews of magnetite formation in prokaryotes as well as on the general ecophysiology of magnetotactic bacteria, see Refs.…”

Section: Introductionmentioning

confidence: 99%

Magnetic irreversibility and the Verwey transition in nanocrystalline bacterial magnetite

et al. 2007

Self Cite

View full text Add to dashboard Cite

The magnetic properties of biologically produced magnetite nanocrystals biomineralized by four different magnetotactic bacteria were compared to those of synthetic magnetite nanocrystals and large, high-quality single crystals. The magnetic feature at the Verwey temperature TV was clearly seen in all nanocrystals, although its sharpness depended on the shape of individual nanoparticles and whether or not the particles were arranged in magnetosome chains. The transition was broader in the individual superparamagnetic nanoparticles for which TB < TV, where TB is the superparamagnetic blocking temperature. For nanocrystals organized in chains, the effective blocking temperature TB > TV and the Verwey transition is sharply defined. No correlation between particle size and TV was found. Furthermore, measurements of M (H,T,time) suggest that magnetosome chains behave as long magnetic dipoles where the local magnetic field is directed along the chain. This result confirms that time-logarithmic magnetic relaxation is due to the collective (dipolar) nature of the barrier for magnetic moment reorientation. The magnetic properties of biologically produced magnetite nanocrystals biomineralized by four different magnetotactic bacteria were compared to those of synthetic magnetite nanocrystals and large, high-quality single crystals. The magnetic feature at the Verwey temperature T V was clearly seen in all nanocrystals, although its sharpness depended on the shape of individual nanoparticles and whether or not the particles were arranged in magnetosome chains. The transition was broader in the individual superparamagnetic nanoparticles for which T B Ͻ T V , where T B is the superparamagnetic blocking temperature. For nanocrystals organized in chains, the effective blocking temperature T B Ͼ T V and the Verwey transition is sharply defined. No correlation between particle size and T V was found. Furthermore, measurements of M͑H , T , time͒ suggest that magnetosome chains behave as long magnetic dipoles where the local magnetic field is directed along the chain. This result confirms that time-logarithmic magnetic relaxation is due to the collective ͑dipolar͒ nature of the barrier for magnetic moment reorientation.

show abstract

Magnetosome formation in prokaryotes

Cited by 1,048 publications

References 129 publications

Chains of Magnetosomes Extracted from AMB-1 Magnetotactic Bacteria for Application in Alternative Magnetic Field Cancer Therapy

Chains of Magnetosomes Extracted from AMB-1 Magnetotactic Bacteria for Application in Alternative Magnetic Field Cancer Therapy

Morphological Transformations in the Magnetite Biomineralizing Protein Mms6 in Iron Solutions: A Small-Angle X-ray Scattering Study

Magnetic irreversibility and the Verwey transition in nanocrystalline bacterial magnetite

Contact Info

Product

Resources

About