Magnetite in Freshwater Magnetotactic Bacteria

Frankel, Richard B.; Blakemore, Richard P.; Wolfe, R. S.

doi:10.1126/science.203.4387.1355

Cited by 532 publications

(305 citation statements)

References 10 publications

(8 reference statements)

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“…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.…”

Section: Introductionmentioning

confidence: 99%

Magnetic irreversibility and the Verwey transition in nanocrystalline bacterial magnetite

Prozorov

Mallapragada

et al. 2007

Phys. Rev. B

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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.

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Section: Introductionmentioning

confidence: 99%

Magnetic irreversibility and the Verwey transition in nanocrystalline bacterial magnetite

Prozorov

Mallapragada

et al. 2007

Phys. Rev. B

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“…This circle is an indicative of an organic membrane [266] that mainly consists of phospholipids and proteins. [272] Iron oxide [273] or/and iron sulfide mineral [274] constitute the inorganic core of magnetosomes. Different crystal habits or morphologies of magnetic crystals have been observed in MTB by various forms of electron microscopy.…”

Section: Bacteria Mediated Synthesis Of Magnetite Nanoparticlesmentioning

confidence: 99%

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

Mosayebi

Kiyasatfar

Laurent

2017

Adv Healthcare Materials

192

171

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In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non‐invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state‐of‐the‐art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half‐life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio–nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi‐modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.

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“…Certain unicellular microorganisms such as magnetotactic bacteria (MTB) have the ability to synthesize chains of mineral crystals (Ruder et al, 2012), each of which is enveloped by individual lipid bilayers in organelles known as magnetosomes (Frankel et al, 1979). These magnetosome inclusions render these creatures a model organism to study compartmentalization in prokaryotes (Komeili, 2012), and the formation mechanisms of these structurally organized magnetosomes under genetic control have been elucidated (Komeili et al, 2004(Komeili et al, , 2006Scheffel et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Sudden motility reversal indicates sensing of magnetic field gradients in Magnetospirillum magneticum AMB-1 strain

et al. 2014

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Many motile unicellular organisms have evolved specialized behaviors for detecting and responding to environmental cues such as chemical gradients (chemotaxis) and oxygen gradients (aerotaxis). Magnetotaxis is found in magnetotactic bacteria and it is defined as the passive alignment of these cells to the geomagnetic field along with active swimming. Herein we show that Magnetospirillum magneticum (AMB-1) show a unique set of responses that indicates they sense and respond not only to the direction of magnetic fields by aligning and swimming, but also to changes in the magnetic field or magnetic field gradients. We present data showing that AMB-1 cells exhibit sudden motility reversals when we impose them to local magnetic field gradients. Our system employs permalloy (Ni 80 Fe 20 ) islands to curve and diverge the magnetic field lines emanating from our custom-designed Helmholtz coils in the vicinity of the islands (creating a drop in the field across the islands). The three distinct movements we have observed as they approach the permalloy islands are: unidirectional, single reverse and double reverse. Our findings indicate that these reverse movements occur in response to magnetic field gradients. In addition, using a permanent magnet we found further evidence that supports this claim. Motile AMB-1 cells swim away from the north and south poles of a permanent magnet when the magnet is positioned less than B30 mm from the droplet of cells. All together, these results indicate previously unknown response capabilities arising from the magnetic sensing systems of AMB-1 cells. These responses could enable them to cope with magnetic disturbances that could in turn potentially inhibit their efficient search for nutrients.

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Magnetite in Freshwater Magnetotactic Bacteria

Cited by 532 publications

References 10 publications

Magnetic irreversibility and the Verwey transition in nanocrystalline bacterial magnetite

Magnetic irreversibility and the Verwey transition in nanocrystalline bacterial magnetite

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

Sudden motility reversal indicates sensing of magnetic field gradients in Magnetospirillum magneticum AMB-1 strain

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