Magnetosome vesicles are present before magnetite formation, and MamA is required for their activation

Komeili, Arash; Vali, Hojatollah; Beveridge, Terrance; Newman, Dianne K.

doi:10.1073/pnas.0400391101

Cited by 309 publications

(368 citation statements)

References 29 publications

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“…and corresponds to Mam22 in M. magnetotacticum MS-1 (Okuda et al 1996) and MamA in M. gryphiswaldense MSR-1 (Grünberg et al 2001). A mutant strain harbouring the defected gene encoding this protein showed lesser BacMP formation in comparison with its wild-type counterpart, suggesting that the protein may be required for the activation of BacMP vesicles (Komeili et al 2004). Taoka et al (2006) recently reported the presence of a novel matrix surrounding a chain of BacMPs.…”

Section: Protein Analyses Of the Bacmp Membranementioning

confidence: 99%

Formation of magnetite by bacteria and its application

Arakaki

Nakazawa

Nemoto

et al. 2008

J. R. Soc. Interface.

220

176

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Magnetic particles offer high technological potential since they can be conveniently collected with an external magnetic field. Magnetotactic bacteria synthesize bacterial magnetic particles (BacMPs) with well-controlled size and morphology. BacMPs are individually covered with thin organic membrane, which confers high and even dispersion in aqueous solutions compared with artificial magnetites, making them ideal biotechnological materials. Recent molecular studies including genome sequence, mutagenesis, gene expression and proteome analyses indicated a number of genes and proteins which play important roles for BacMP biomineralization. Some of the genes and proteins identified from these studies have allowed us to express functional proteins efficiently onto BacMPs, through genetic engineering, permitting the preservation of the protein activity, leading to a simple preparation of functional protein-magnetic particle complexes. They were applicable to high-sensitivity immunoassay, drug screening and cell separation. Furthermore, fully automated single nucleotide polymorphism discrimination and DNA recovery systems have been developed to use these functionalized BacMPs. The nano-sized fine magnetic particles offer vast potential in new nano-techniques.

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Section: Protein Analyses Of the Bacmp Membranementioning

confidence: 99%

Formation of magnetite by bacteria and its application

Arakaki

Nakazawa

Nemoto

et al. 2008

J. R. Soc. Interface.

220

176

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“…The grids were examined at moderate magnification on a Zeiss-9 TEM to assess chain linearity vs. clumping. For the experiments with aligned chains, the samples were prepared by negative staining or conventional embedding procedures (e.g., [35]) as described elsewhere. We stabilized magnetotactic bacteria with a strong background magnetic field maintained during the entire fixation and TEM sample preparation process to prevent chain collapse with a pair of NdFeB disc magnets, 2 mm in diameter separated by a 3.7 mm gap, which produced a measured minimum magnetic field in the center of ~100 mT 5 (see Fig.…”

Section: Transmission Electron Microscopymentioning

confidence: 99%

“…Samples were prepared by negative staining or conventional embedding procedures (e.g., [35]). All cells collected by magnets were first fixed with 1% gluteraldehyde and 4% paraformaldehyde in 0.1 M phosphate buffer (PB) at pH.7.4 for half an hour.…”

Section: Transmission Electron Microscopymentioning

confidence: 99%

Experimental observation of magnetosome chain collapse in magnetotactic bacteria: Sedimentological, paleomagnetic, and evolutionary implications

Kobayashi

Kirschvink

Nash

et al. 2006

Earth and Planetary Science Letters

101

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“…6 in Faivre and Schuler 19 ). Despite decades of intense research, this process is still not fully understood 2,18,20,21 . Biological macromolecules, specifically membrane bound proteins in magnetotactic bacteria, play an important role in templating biomineralized magnetosome magnetite crystals, although their exact role remains unclear [14][15][16]21 .…”

mentioning

confidence: 99%

Correlative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging

et al. 2015

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Magnetotactic bacteria biomineralize ordered chains of uniform, membrane-bound magnetite or greigite nanocrystals that exhibit nearly perfect crystal structures and species-specific morphologies. Transmission electron microscopy (TEM) is a critical technique for providing information regarding the organization of cellular and magnetite structures in these microorganisms. However, conventional TEM can only be used to image air-dried or vitrified bacteria removed from their natural environment. Here we present a correlative scanning TEM (STEM) and fluorescence microscopy technique for imaging viable cells of Magnetospirillum magneticum strain AMB-1 in liquid using an in situ fluid cell TEM holder. Fluorescently labeled cells were immobilized on microchip window surfaces and visualized in a fluid cell with STEM, followed by correlative fluorescence imaging to verify their membrane integrity. Notably, the post-STEM fluorescence imaging indicated that the bacterial cell wall membrane did not sustain radiation damage during STEM imaging at low electron dose conditions. We investigated the effects of radiation damage and sample preparation on the bacteria viability and found that approximately 50% of the bacterial membranes remained intact after an hour in the fluid cell, decreasing to ,30% after two hours. These results represent a first step toward in vivo studies of magnetite biomineralization in magnetotactic bacteria.B iomineralization is a widespread biological phenomenon occurring in living organisms ranging from single cells to complex multicellular organisms. Biomineralization of inorganic materials in single cell organisms is an ideal system for studying fundamental mechanisms of biomineralization 1 . Model systems range from prokaryotic organisms, such as magnetite formation in magnetotactic bacteria 2-4 , to eukaryotic organisms, such as silica biomineralization in diatoms 5,6 . Understanding biomineralization in these organisms in terms of crystal nucleation and growth, as well as the involvement of biological macromolecules and cellular processes, is of fundamental interest to scientists as similar principles can be used to develop synthetic nanomaterials.Magnetite biomineralization by magnetotactic bacteria is a topic of great interest in nanotechnology 7-12 , functional materials [11][12][13][14][15][16] , and astrobiology 17 . Magnetotactic bacteria take up soluble iron species that they use to biomineralize chains of magnetite nanocrystals, known as magnetosomes, in intracellular membrane vesicles 2 . The nanocrystals have nearly perfect mineral crystal structures with consistent species-specific morphologies, leading to well-defined magnetic properties 2,3,9,12,18,19 . As a result, magnetotactic bacteria are one of the best model systems for investigating the molecular mechanisms of biomineralization. Magnetite biomineralization in these bacteria is a complex process involving a number of steps including cellular uptake and reduction of ferric ions, complexation of the iron with membrane proteins, an...

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Magnetosome vesicles are present before magnetite formation, and MamA is required for their activation

Cited by 309 publications

References 29 publications

Formation of magnetite by bacteria and its application

Formation of magnetite by bacteria and its application

Experimental observation of magnetosome chain collapse in magnetotactic bacteria: Sedimentological, paleomagnetic, and evolutionary implications

Correlative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging

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