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1
Taoka, Azuma, Ryuji Asada, Hideaki Sasaki, Kazushi Anzawa, Long-Fei Wu, and Yoshihiro Fukumori. "Spatial Localizations of Mam22 and Mam12 in the Magnetosomes of Magnetospirillum magnetotacticum." Journal of Bacteriology 188, no. 11 (June 1, 2006): 3805–12. http://dx.doi.org/10.1128/jb.00020-06.
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ABSTRACT Magnetospirillum magnetotacticum possesses intracellular magnetite particles with a chain-like structure, termed magnetosomes. The bacterium expresses 22-kDa and 12-kDa magnetosome-associated proteins, termed Mam22 (MamA) and Mam12 (MamC), respectively. In this study, we investigated the structure of the purified magnetosomes with transmission electron microscopic techniques and found that the magnetosomes consisted of four compartments, i.e., magnetite crystal, magnetosomal membrane, interparticle connection, and magnetosomal matrix. Furthermore, we determined the precise localizations of Mam22 and Mam12 using immunogold staining of the purified magnetosomes and ultrathin sections of the bacterial cells. Interestingly, most Mam22 existed in the magnetosomal matrix, whereas Mam12 was strictly localized in the magnetosomal membrane. Moreover, the recombinant Mam22 was attached to the magnetosomal matrix of the Mam22-deficient magnetosomes prepared by alkaline treatment, such as 0.1 M Caps-NaOH buffer (pH 11.0). The spatial localization of the magnetosome-associated proteins in the magnetosomal chain provides useful information to elucidate the functional roles of these proteins.
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Lang, Claus, Anna Pollithy, and Dirk Schüler. "Identification of Promoters for Efficient Gene Expression in Magnetospirillum gryphiswaldense." Applied and Environmental Microbiology 75, no. 12 (April 24, 2009): 4206–10. http://dx.doi.org/10.1128/aem.02906-08.
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ABSTRACT To develop an expression system for the magnetotactic bacterium Magnetospirillum gryphiswaldense, we compared gene expression from the widely used Escherichia coli P lac promoter with that from known and predicted genuine M. gryphiswaldense promoters. With the use of green fluorescent protein as a reporter, the highest expression level was observed with the magnetosomal P mamDC promoter. We demonstrate that this promoter can be used for the expression of modified magnetosome proteins to generate “antibody-binding” magnetosomes.
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Lang, Claus, and Dirk Schüler. "Expression of Green Fluorescent Protein Fused to Magnetosome Proteins in Microaerophilic Magnetotactic Bacteria." Applied and Environmental Microbiology 74, no. 15 (June 6, 2008): 4944–53. http://dx.doi.org/10.1128/aem.00231-08.
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ABSTRACT The magnetosomes of magnetotactic bacteria are prokaryotic organelles consisting of a magnetite crystal bounded by a phospholipid bilayer that contains a distinct set of proteins with various functions. Because of their unique magnetic and crystalline properties, magnetosome particles are potentially useful as magnetic nanoparticles in a number of applications, which in many cases requires the coupling of functional moieties to the magnetosome membrane. In this work, we studied the use of green fluorescent protein (GFP) as a reporter for the magnetosomal localization and expression of fusion proteins in the microaerophilic Magnetospirillum gryphiswaldense by flow cytometry, fluorescence microscopy, and biochemical analysis. Although optimum conditions for high fluorescence and magnetite synthesis were mutually exclusive, we established oxygen-limited growth conditions, which supported growth, magnetite biomineralization, and GFP fluorophore formation at reasonable rates. Under these optimized conditions, we studied the subcellular localization and expression of the GFP-tagged magnetosome proteins MamC, MamF, and MamG by fluorescence microscopy and immunoblotting. While all fusions specifically localized at the magnetosome membrane, MamC-GFP displayed the strongest expression and fluorescence. MamC-GFP-tagged magnetosomes purified from cells displayed strong fluorescence, which was sensitive to detergents but stable under a wide range of temperature and salt concentrations. In summary, our data demonstrate the use of GFP as a reporter for protein localization under magnetite-forming conditions and the utility of MamC as an anchor for magnetosome-specific display of heterologous gene fusions.
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Lohße, Anna, Isabel Kolinko, Oliver Raschdorf, René Uebe, Sarah Borg, Andreas Brachmann, Jürgen M. Plitzko, Rolf Müller, Youming Zhang, and Dirk Schüler. "Overproduction of Magnetosomes by Genomic Amplification of Biosynthesis-Related Gene Clusters in a Magnetotactic Bacterium." Applied and Environmental Microbiology 82, no. 10 (March 11, 2016): 3032–41. http://dx.doi.org/10.1128/aem.03860-15.
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ABSTRACTMagnetotactic bacteria biosynthesize specific organelles, the magnetosomes, which are membrane-enclosed crystals of a magnetic iron mineral that are aligned in a linear chain. The number and size of magnetosome particles have to be critically controlled to build a sensor sufficiently strong to ensure the efficient alignment of cells within Earth's weak magnetic field while at the same time minimizing the metabolic costs imposed by excessive magnetosome biosynthesis. Apart from their biological function, bacterial magnetosomes have gained considerable interest since they provide a highly useful model for prokaryotic organelle formation and represent biogenic magnetic nanoparticles with exceptional properties. However, potential applications have been hampered by the difficult cultivation of these fastidious bacteria and their poor yields of magnetosomes. In this study, we found that the size and number of magnetosomes within the cell are controlled by many different Mam and Mms proteins. We present a strategy for the overexpression of magnetosome biosynthesis genes in the alphaproteobacteriumMagnetospirillum gryphiswaldenseby chromosomal multiplication of individual and multiple magnetosome gene clusters via transposition. While stepwise amplification of themms6operon resulted in the formation of increasingly larger crystals (increase of ∼35%), the duplication of all major magnetosome operons (mamGFDC,mamAB,mms6, andmamXY, comprising 29 genes in total) yielded an overproducing strain in which magnetosome numbers were 2.2-fold increased. We demonstrate that the tuned expression of themamandmmsclusters provides a powerful strategy for the control of magnetosome size and number, thereby setting the stage for high-yield production of tailored magnetic nanoparticles by synthetic biology approaches.IMPORTANCEBefore our study, it had remained unknown how the upper sizes and numbers of magnetosomes are genetically regulated, and overproduction of magnetosome biosynthesis had not been achieved, owing to the difficulties of large-scale genome engineering in the recalcitrant magnetotactic bacteria. In this study, we established and systematically explored a strategy for the overexpression of magnetosome biosynthesis genes by genomic amplification of single and multiple magnetosome gene clusters via sequential chromosomal insertion by transposition. Our findings also indicate that the expression levels of magnetosome proteins together limit the upper size and number of magnetosomes within the cell. We demonstrate that tuned overexpression of magnetosome gene clusters provides a powerful strategy for the precise control of magnetosome size and number.
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Fischer, Anna, Manuel Schmitz, Barbara Aichmayer, Peter Fratzl, and Damien Faivre. "Structural purity of magnetite nanoparticles in magnetotactic bacteria." Journal of The Royal Society Interface 8, no. 60 (January 19, 2011): 1011–18. http://dx.doi.org/10.1098/rsif.2010.0576.
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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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Lins, Ulysses, Martha R. McCartney, Marcos Farina, Richard B. Frankel, and Peter R. Buseck. "Crystal habits and magnetic microstructures of magnetosomes in coccoid magnetotactic bacteria." Anais da Academia Brasileira de Ciências 78, no. 3 (September 2006): 463–74. http://dx.doi.org/10.1590/s0001-37652006000300007.
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We report on the application of off-axis electron holography and high-resolution TEM to study the crystal habits of magnetosomes and magnetic microstructure in two coccoid morphotypes of magnetotactic bacteria collected from a brackish lagoon at Itaipu, Brazil. Itaipu-1, the larger coccoid organism, contains two separated chains of unusually large magnetosomes; the magnetosome crystals have roughly square projections, lengths up to 250 nm and are slightly elongated along [111] (width/length ratio of about 0.9). Itaipu-3 magnetosome crystals have lengths up to 120 nm, greater elongation along [111] (width/length ~0.6), and prominent corner facets. The results show that Itaipu-1 and Itaipu-3 magnetosome crystal habits are related, differing only in the relative sizes of their crystal facets. In both cases, the crystals are aligned with their [111] elongation axes parallel to the chain direction. In Itaipu-1, but not Itaipu-3, crystallographic positioning perpendicular to [111] of successive crystals in the magnetosome chain appears to be under biological control. Whereas the large magnetosomes in Itaipu-1 are metastable, single-magnetic domains, magnetosomes in Itaipu-3 are permanent, single-magnetic domains, as in most magnetotactic bacteria.
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Zhu, Xiaohui, Adam P. Hitchcock, Dennis A. Bazylinski, Peter Denes, John Joseph, Ulysses Lins, Stefano Marchesini, Hung-Wei Shiu, Tolek Tyliszczak, and David A. Shapiro. "Measuring spectroscopy and magnetism of extracted and intracellular magnetosomes using soft X-ray ptychography." Proceedings of the National Academy of Sciences 113, no. 51 (December 7, 2016): E8219—E8227. http://dx.doi.org/10.1073/pnas.1610260114.
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Characterizing the chemistry and magnetism of magnetotactic bacteria (MTB) is an important aspect of understanding the biomineralization mechanism and function of the chains of magnetosomes (Fe3O4nanoparticles) found in such species. Images and X-ray absorption spectra (XAS) of magnetosomes extracted from, and magnetosomes in, wholeMagnetovibrio blakemoreistrain MV-1 cells have been recorded using soft X-ray ptychography at the Fe 2p edge. A spatial resolution of 7 nm is demonstrated. Precursor-like and immature magnetosome phases in a whole MV-1 cell were visualized, and their Fe 2p spectra were measured. Based on these results, a model for the pathway of magnetosome biomineralization for MV-1 is proposed. Fe 2p X-ray magnetic circular dichroism (XMCD) spectra have been derived from ptychography image sequences recorded using left and right circular polarization. The shape of the XAS and XMCD signals in the ptychographic absorption spectra of both sample types is identical to the shape and signals measured with conventional bright-field scanning transmission X-ray microscope. A weaker and inverted XMCD signal was observed in the ptychographic phase spectra of the extracted magnetosomes. The XMCD ptychographic phase spectrum of the intracellular magnetosomes differed from the ptychographic phase spectrum of the extracted magnetosomes. These results demonstrate that spectro-ptychography offers a superior means of characterizing the chemical and magnetic properties of MTB at the individual magnetosome level.
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Arakaki, Atsushi, Daiki Kikuchi, Masayoshi Tanaka, Ayana Yamagishi, Takuto Yoda, and Tadashi Matsunaga. "Comparative Subcellular Localization Analysis of Magnetosome Proteins Reveals a Unique Localization Behavior of Mms6 Protein onto Magnetite Crystals." Journal of Bacteriology 198, no. 20 (August 1, 2016): 2794–802. http://dx.doi.org/10.1128/jb.00280-16.
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ABSTRACTThe magnetosome is an organelle specialized for inorganic magnetite crystal synthesis in magnetotactic bacteria. The complex mechanism of magnetosome formation is regulated by magnetosome proteins in a stepwise manner. Protein localization is a key step for magnetosome development; however, a global study of magnetosome protein localization remains to be conducted. Here, we comparatively analyzed the subcellular localization of a series of green fluorescent protein (GFP)-tagged magnetosome proteins. The protein localizations were categorized into 5 groups (short-length linear, middle-length linear, long-length linear, cell membrane, and intracellular dispersing), which were related to the protein functions. Mms6, which regulates magnetite crystal growth, localized along magnetosome chain structures under magnetite-forming (microaerobic) conditions but was dispersed in the cell under nonforming (aerobic) conditions. Correlative fluorescence and electron microscopy analyses revealed that Mms6 preferentially localized to magnetosomes enclosing magnetite crystals. We suggest that a highly organized spatial regulation mechanism controls magnetosome protein localization during magnetosome formation in magnetotactic bacteria.IMPORTANCEMagnetotactic bacteria synthesize magnetite (Fe3O4) nanocrystals in a prokaryotic organelle called the magnetosome. This organelle is formed using various magnetosome proteins in multiple steps, including vesicle formation, magnetosome alignment, and magnetite crystal formation, to provide compartmentalized nanospaces for the regulation of iron concentrations and redox conditions, enabling the synthesis of a morphologically controlled magnetite crystal. Thus, to rationalize the complex organelle development, the localization of magnetosome proteins is considered to be highly regulated; however, the mechanisms remain largely unknown. Here, we performed comparative localization analysis of magnetosome proteins that revealed the presence of a spatial regulation mechanism within the linear structure of magnetosomes. This discovery provides evidence of a highly regulated protein localization mechanism for this bacterial organelle development.
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Honda, Toru, Takayuki Yasuda, Tsuyoshi Tanaka, Koji Hagiwara, Tohru Arai, and Tomoko Yoshino. "Functional Expression of Full-Length TrkA in the Prokaryotic Host Magnetospirillum magneticum AMB-1 by Using a Magnetosome Display System." Applied and Environmental Microbiology 81, no. 4 (December 19, 2014): 1472–76. http://dx.doi.org/10.1128/aem.03112-14.
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ABSTRACTTropomyosin receptor kinase A (TrkA), a receptor tyrosine kinase, is known to be associated with various diseases. Thus, TrkA has become a major drug-screening target for these diseases. Despite the fact that the production of recombinant proteins by prokaryotic hosts has advantages, such as fast growth and ease of genetic engineering, the efficient production of functional receptor tyrosine kinase by prokaryotic hosts remains a major experimental challenge. Here, we report the functional expression of full-length TrkA on magnetosomes inMagnetospirillum magneticumAMB-1 by using a magnetosome display system. TrkA was fused with the magnetosome-localized protein Mms13 and expressed on magnetosome surfaces. Recombinant TrkA showed both nerve growth factor (NGF)-binding and autophosphorylation activities. TrkA expressed on magnetosomes has the potential to be used, not only for further functional analysis of TrkA, but also for ligand screening.
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Józefczak, Arkadiusz, Tomasz Hornowski, Anita Król, Matúš Molčan, Błażej Leszczyński, and Milan Timko. "The Effect of Sonication on Acoustic Properties of Biogenic Ferroparticle Suspension." Archives of Acoustics 41, no. 1 (March 1, 2016): 161–68. http://dx.doi.org/10.1515/aoa-2016-0016.
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Abstract Superparamagnetic iron oxide nanoparticles (SPION) synthesised chemically usually need the modification of the particle surface. Other natural sources of magnetic particles are various magnetotactic bacteria. Magnetosomes isolated from magnetotactic bacteria are organelles consisting of magnetite (Fe3O4) or greigite (Fe3S4) crystals enclosed by a biological membrane. Magnetotactic bacteria produce their magnetic particles in chains. The process of isolation of magnetosome chains from the body of bacteria consists of a series of cycles of centrifugation and magnetic decantation. Using a high-energy ultrasound it is possible to break the magnetosome chains into individual nanoparticles – magnetosomes. This study presents the effect of sonication of magnetosome suspension on their acoustic properties, that is speed and attenuation of the sound. Acoustic propagation parameters are measured using ultrasonic spectroscopy based on FFT spectral analysis of the received pulses. The speed and attenuation of ultrasonic waves in magnetosome suspensions are analysed as a function of frequency, temperature, magnetic field intensity, and the angle between the direction of the wave and the direction of the field.
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Vargas, Gabriele, Jefferson Cypriano, Tarcisio Correa, Pedro Leão, Dennis Bazylinski, and Fernanda Abreu. "Applications of Magnetotactic Bacteria, Magnetosomes and Magnetosome Crystals in Biotechnology and Nanotechnology: Mini-Review." Molecules 23, no. 10 (September 24, 2018): 2438. http://dx.doi.org/10.3390/molecules23102438.
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Magnetotactic bacteria (MTB) biomineralize magnetosomes, which are defined as intracellular nanocrystals of the magnetic minerals magnetite (Fe3O4) or greigite (Fe3S4) enveloped by a phospholipid bilayer membrane. The synthesis of magnetosomes is controlled by a specific set of genes that encode proteins, some of which are exclusively found in the magnetosome membrane in the cell. Over the past several decades, interest in nanoscale technology (nanotechnology) and biotechnology has increased significantly due to the development and establishment of new commercial, medical and scientific processes and applications that utilize nanomaterials, some of which are biologically derived. One excellent example of a biological nanomaterial that is showing great promise for use in a large number of commercial and medical applications are bacterial magnetite magnetosomes. Unlike chemically-synthesized magnetite nanoparticles, magnetosome magnetite crystals are stable single-magnetic domains and are thus permanently magnetic at ambient temperature, are of high chemical purity, and display a narrow size range and consistent crystal morphology. These physical/chemical features are important in their use in biotechnological and other applications. Applications utilizing magnetite-producing MTB, magnetite magnetosomes and/or magnetosome magnetite crystals include and/or involve bioremediation, cell separation, DNA/antigen recovery or detection, drug delivery, enzyme immobilization, magnetic hyperthermia and contrast enhancement of magnetic resonance imaging. Metric analysis using Scopus and Web of Science databases from 2003 to 2018 showed that applied research involving magnetite from MTB in some form has been focused mainly in biomedical applications, particularly in magnetic hyperthermia and drug delivery.
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Cui, Kaixuan, Hongmiao Pan, Jianwei Chen, Jia Liu, Yicong Zhao, Si Chen, Wenyan Zhang, Tian Xiao, and Long-Fei Wu. "A Novel Isolate of Spherical Multicellular Magnetotactic Prokaryotes Has Two Magnetosome Gene Clusters and Synthesizes Both Magnetite and Greigite Crystals." Microorganisms 10, no. 5 (April 28, 2022): 925. http://dx.doi.org/10.3390/microorganisms10050925.
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Multicellular magnetotactic prokaryotes (MMPs) are a unique group of magnetotactic bacteria that are composed of 10–100 individual cells and show coordinated swimming along magnetic field lines. MMPs produce nanometer-sized magnetite (Fe3O4) and/or greigite (Fe3S4) crystals—termed magnetosomes. Two types of magnetosome gene cluster (MGC) that regulate biomineralization of magnetite and greigite have been found. Here, we describe a dominant spherical MMP (sMMP) species collected from the intertidal sediments of Jinsha Bay, in the South China Sea. The sMMPs were 4.78 ± 0.67 μm in diameter, comprised 14–40 cells helical symmetrically, and contained bullet-shaped magnetite and irregularly shaped greigite magnetosomes. Two sets of MGCs, one putatively related to magnetite biomineralization and the other to greigite biomineralization, were identified in the genome of the sMMP, and two sets of paralogous proteins (Mam and Mad) that may function separately and independently in magnetosome biomineralization were found. Phylogenetic analysis indicated that the sMMPs were affiliated with Deltaproteobacteria. This is the first direct report of two types of magnetosomes and two sets of MGCs being detected in the same sMMP. The study provides new insights into the mechanism of biomineralization of magnetosomes in MMPs, and the evolutionary origin of MGCs.
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Leila, Hatami Giklou Jajan, Mohsen Abolhassani, Seyed Nezamedin Hosseini, Behzad Ghareyazie, Leila Ma'mani, Delaram Doroud, Ava Behrouzi, and Masoud Ghorbani. "Effects of Electromagnetic Fields Exposure on the Production of Nanosized Magnetosome, Elimination of Free Radicals and Antioxidant Defense Systems in Magnetospirillum gryphiswaldense MSR-1." Journal of Nano Research 58 (June 2019): 20–31. http://dx.doi.org/10.4028/www.scientific.net/jnanor.58.20.
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Magnetotactic bacteria integrated magnetosomes, which are unique organelles that contain nanosized crystals of biogenic magnetic iron minerals with the ability to respond to the external magnetic fields. The biogenic magnetic nanoparticles (magnetosomes) show high biocompatibility in medical applications especially as scavengers to eliminate intracellular reactive oxygen species. The aim of this study was to highlight the impact of magnetosome formation and antioxidant systems in the suppression of oxidative stress on the magnetotactic bacteria cells. To assess the changes in ROS levels under different magnetic field intensity conditions, cells were cultured under the microaerobic condition in medium containing the high and low intensity of magnetic field. Treatment of magnetic field with an intensity of 500 mT during 50 hours bionormalization process of magnetotactic bacteria increased the antioxidant enzyme activity for eliminating of free radicals by 64%. We concluded that magnetosomes production plays an important role in decreasing or eliminating ROS. This is the first study to demonstrate that the magnetic field assisted magnetosome formation and antioxidants defense systems inMagnetospirillum gryphiswaldenseMSR-1.
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Ohuchi, Shoji, and Dirk Schüler. "In Vivo Display of a Multisubunit Enzyme Complex on Biogenic Magnetic Nanoparticles." Applied and Environmental Microbiology 75, no. 24 (October 16, 2009): 7734–38. http://dx.doi.org/10.1128/aem.01640-09.
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ABSTRACT Magnetosomes are unique bacterial organelles comprising membrane-enveloped magnetic crystals produced by magnetotactic bacteria. Because of several desirable chemical and physical properties, magnetosomes would be ideal scaffolds on which to display highly complicated biological complexes artificially. As a model experiment for the functional expression of a multisubunit complex on magnetosomes, we examined the display of a chimeric bacterial RNase P enzyme composed of the protein subunit (C5) of Escherichia coli RNase P and the endogenous RNA subunit by expressing a translational fusion of C5 with MamC, a known magnetosome protein, in the magnetotactic bacterium Magnetospirillum gryphiswaldense. As intended, the purified C5 fusion magnetosomes, but not wild-type magnetosomes, showed apparent RNase P activity and the association of a typical bacterial RNase P RNA. Our results demonstrate for the first time that magnetosomes can be employed as scaffolds for the display of multisubunit complexes.
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Pfeiffer, Daniel, Mauricio Toro-Nahuelpan, Ram Prasad Awal, Frank-Dietrich Müller, Marc Bramkamp, Jürgen M. Plitzko, and Dirk Schüler. "A bacterial cytolinker couples positioning of magnetic organelles to cell shape control." Proceedings of the National Academy of Sciences 117, no. 50 (November 30, 2020): 32086–97. http://dx.doi.org/10.1073/pnas.2014659117.
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Magnetotactic bacteria maneuver within the geomagnetic field by means of intracellular magnetic organelles, magnetosomes, which are aligned into a chain and positioned at midcell by a dedicated magnetosome-specific cytoskeleton, the “magnetoskeleton.” However, how magnetosome chain organization and resulting magnetotaxis is linked to cell shape has remained elusive. Here, we describe the cytoskeletal determinant CcfM (curvature-inducing coiled-coil filament interacting with the magnetoskeleton), which links the magnetoskeleton to cell morphology regulation in Magnetospirillum gryphiswaldense. Membrane-anchored CcfM localizes in a filamentous pattern along regions of inner positive-cell curvature by its coiled-coil motifs, and independent of the magnetoskeleton. CcfM overexpression causes additional circumferential localization patterns, associated with a dramatic increase in cell curvature, and magnetosome chain mislocalization or complete chain disruption. In contrast, deletion of ccfM results in decreased cell curvature, impaired cell division, and predominant formation of shorter, doubled chains of magnetosomes. Pleiotropic effects of CcfM on magnetosome chain organization and cell morphology are supported by the finding that CcfM interacts with the magnetoskeleton-related MamY and the actin-like MamK via distinct motifs, and with the cell shape-related cytoskeleton via MreB. We further demonstrate that CcfM promotes motility and magnetic alignment in structured environments, and thus likely confers a selective advantage in natural habitats of magnetotactic bacteria, such as aquatic sediments. Overall, we unravel the function of a prokaryotic cytoskeletal constituent that is widespread in magnetic and nonmagnetic spirilla-shaped Alphaproteobacteria.
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Pollithy, Anna, Tina Romer, Claus Lang, Frank D. Müller, Jonas Helma, Heinrich Leonhardt, Ulrich Rothbauer, and Dirk Schüler. "Magnetosome Expression of Functional Camelid Antibody Fragments (Nanobodies) in Magnetospirillum gryphiswaldense." Applied and Environmental Microbiology 77, no. 17 (July 15, 2011): 6165–71. http://dx.doi.org/10.1128/aem.05282-11.
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ABSTRACTNumerous applications of conventional and biogenic magnetic nanoparticles (MNPs), such as in diagnostics, immunomagnetic separations, and magnetic cell labeling, require the immobilization of antibodies. This is usually accomplished by chemical conjugation, which, however, has several disadvantages, such as poor efficiency and the need for coupling chemistry. Here, we describe a novel strategy to display a functional camelid antibody fragment (nanobody) from an alpaca (Lama pacos) on the surface of bacterial biogenic magnetic nanoparticles (magnetosomes). Magnetosome-specific expression of a red fluorescent protein (RFP)-binding nanobody (RBP)in vivowas accomplished by genetic fusion of RBP to the magnetosome protein MamC in the magnetite-synthesizing bacteriumMagnetospirillum gryphiswaldense. We demonstrate that isolated magnetosomes expressing MamC-RBP efficiently recognize and bind their antigenin vitroand can be used for immunoprecipitation of RFP-tagged proteins and their interaction partners from cell extracts. In addition, we show that coexpression of monomeric RFP (mRFP or its variant mCherry) and MamC-RBP results in intracellular recognition and magnetosome recruitment of RFP within living bacteria. The intracellular expression of a functional nanobody targeted to a specific bacterial compartment opens new possibilities forin vivosynthesis of MNP-immobilized nanobodies. Moreover, intracellular nanotraps can be generated to manipulate bacterial structures in live cells.
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Borg, Sarah, Julia Hofmann, Anna Pollithy, Claus Lang, and Dirk Schüler. "New Vectors for Chromosomal Integration Enable High-Level Constitutive or Inducible Magnetosome Expression of Fusion Proteins in Magnetospirillum gryphiswaldense." Applied and Environmental Microbiology 80, no. 8 (February 14, 2014): 2609–16. http://dx.doi.org/10.1128/aem.00192-14.
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ABSTRACTThe alphaproteobacteriumMagnetospirillum gryphiswaldensebiomineralizes magnetosomes, which consist of monocrystalline magnetite cores enveloped by a phospholipid bilayer containing specific proteins. Magnetosomes represent magnetic nanoparticles with unprecedented magnetic and physicochemical characteristics. These make them potentially useful in a number of biotechnological and biomedical applications. Further functionalization can be achieved by expression of foreign proteins via genetic fusion to magnetosome anchor peptides. However, the available genetic tool set for strong and controlled protein expression in magnetotactic bacteria is very limited. Here, we describe versatile vectors for either inducible or high-level constitutive expression of proteins inM. gryphiswaldense. The combination of an engineered native PmamDCpromoter with a codon-optimizedegfpgene (Mag-egfp) resulted in an 8-fold increase in constitutive expression and in brighter fluorescence. We further demonstrate that the widely used Ptetpromoter is functional and tunable inM. gryphiswaldense. Stable and uniform expression of the EGFP and β-glucuronidase (GusA) reporters was achieved by single-copy chromosomal insertion via Tn5-mediated transposition. In addition, gene duplication by Mag-EGFP–EGFP fusions to MamC resulted in further increased magnetosome expression and fluorescence. Between 80 and 210 (for single MamC–Mag-EGFP) and 200 and 520 (for MamC–Mag-EGFP–EGFP) GFP copies were estimated to be expressed per individual magnetosome particle.
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Li, Jinhua, Nicolas Menguy, Marie-Anne Arrio, Philippe Sainctavit, Amélie Juhin, Yinzhao Wang, Haitao Chen, et al. "Controlled cobalt doping in the spinel structure of magnetosome magnetite: new evidences from element- and site-specific X-ray magnetic circular dichroism analyses." Journal of The Royal Society Interface 13, no. 121 (August 2016): 20160355. http://dx.doi.org/10.1098/rsif.2016.0355.
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The biomineralization of magnetite nanocrystals (called magnetosomes) by magnetotactic bacteria (MTB) has attracted intense interest in biology, geology and materials science due to the precise morphology of the particles, the chain-like assembly and their unique magnetic properties. Great efforts have been recently made in producing transition metal-doped magnetosomes with modified magnetic properties for a range of applications. Despite some successful outcomes, the coordination chemistry and magnetism of such metal-doped magnetosomes still remain largely unknown. Here, we present new evidences from X-ray magnetic circular dichroism (XMCD) for element- and site-specific magnetic analyses that cobalt is incorporated in the spinel structure of the magnetosomes within Magnetospirillum magneticum AMB-1 through the replacement of Fe 2+ ions by Co 2+ ions in octahedral ( O h ) sites of magnetite. Both XMCD at Fe and Co L 2,3 edges, and energy-dispersive X-ray spectroscopy on transmission electron microscopy analyses reveal a heterogeneous distribution of cobalt occurring either in different particles or inside individual particles. Compared with non-doped one, cobalt-doped magnetosome sample has lower Verwey transition temperature and larger magnetic coercivity, related to the amount of doped cobalt. This study also demonstrates that the addition of trace cobalt in the growth medium can significantly improve both the cell growth and the magnetosome formation within M. magneticum AMB-1. Together with the cobalt occupancy within the spinel structure of magnetosomes, this study indicates that MTB may provide a promising biomimetic system for producing chains of metal-doped single-domain magnetite with an appropriate tuning of the magnetic properties for technological and biomedical applications.
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Gareev, Kamil G., Denis S. Grouzdev, Peter V. Kharitonskii, Demid A. Kirilenko, Andrei Kosterov, Veronika V. Koziaeva, Vladimir S. Levitskii, et al. "Magnetic Properties of Bacterial Magnetosomes Produced by Magnetospirillum caucaseum SO-1." Microorganisms 9, no. 9 (August 31, 2021): 1854. http://dx.doi.org/10.3390/microorganisms9091854.
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In this study, the magnetic properties of magnetosomes isolated from lyophilized magnetotactic bacteria Magnetospirillum caucaseum SO-1 were assessed for the first time. The shape and size of magnetosomes and cell fragments were studied by electron microscopy and dynamic light scattering techniques. Phase and elemental composition were analyzed by X-ray and electron diffraction and Raman spectroscopy. Magnetic properties were studied using vibrating sample magnetometry and electron paramagnetic resonance spectroscopy. Theoretical analysis of the magnetic properties was carried out using the model of clusters of magnetostatically interacting two-phase particles and a modified method of moments for a system of dipole–dipole-interacting uniaxial particles. Magnetic properties were controlled mostly by random aggregates of magnetosomes, with a minor contribution from preserved magnetosome chains. Results confirmed the high chemical stability and homogeneity of bacterial magnetosomes in comparison to synthetic iron oxide magnetic nanoparticles.
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Singappuli-Arachchige, Dilini, Shuren Feng, Lijun Wang, Pierre E. Palo, Samuel O. Shobade, Michelle Thomas, and Marit Nilsen-Hamilton. "The Magnetosome Protein, Mms6 from Magnetospirillum magneticum Strain AMB-1, Is a Lipid-Activated Ferric Reductase." International Journal of Molecular Sciences 23, no. 18 (September 7, 2022): 10305. http://dx.doi.org/10.3390/ijms231810305.
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Magnetosomes of magnetotactic bacteria consist of magnetic nanocrystals with defined morphologies enclosed in vesicles originated from cytoplasmic membrane invaginations. Although many proteins are involved in creating magnetosomes, a single magnetosome protein, Mms6 from Magnetospirillum magneticum strain AMB-1, can direct the crystallization of magnetite nanoparticles in vitro. The in vivo role of Mms6 in magnetosome formation is debated, and the observation that Mms6 binds Fe3+ more tightly than Fe2+ raises the question of how, in a magnetosome environment dominated by Fe3+, Mms6 promotes the crystallization of magnetite, which contains both Fe3+ and Fe2+. Here we show that Mms6 is a ferric reductase that reduces Fe3+ to Fe2+ using NADH and FAD as electron donor and cofactor, respectively. Reductase activity is elevated when Mms6 is integrated into either liposomes or bicelles. Analysis of Mms6 mutants suggests that the C-terminal domain binds iron and the N-terminal domain contains the catalytic site. Although Mms6 forms multimers that involve C-terminal and N-terminal domain interactions, a fusion protein with ubiquitin remains a monomer and displays reductase activity, which suggests that the catalytic site is fully in the monomer. However, the quaternary structure of Mms6 appears to alter the iron binding characteristics of the C-terminal domain. These results are consistent with a hypothesis that Mms6, a membrane protein, promotes the formation of magnetite in vivo by a mechanism that involves reducing iron.
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Katzmann, E., M. Eibauer, W. Lin, Y. Pan, J. M. Plitzko, and D. Schüler. "Analysis of Magnetosome Chains in Magnetotactic Bacteria by Magnetic Measurements and Automated Image Analysis of Electron Micrographs." Applied and Environmental Microbiology 79, no. 24 (October 4, 2013): 7755–62. http://dx.doi.org/10.1128/aem.02143-13.
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ABSTRACTMagnetotactic bacteria (MTB) align along the Earth's magnetic field by the activity of intracellular magnetosomes, which are membrane-enveloped magnetite or greigite particles that are assembled into well-ordered chains. Formation of magnetosome chains was found to be controlled by a set of specific proteins inMagnetospirillum gryphiswaldenseand other MTB. However, the contribution of abiotic factors on magnetosome chain assembly has not been fully explored. Here, we first analyzed the effect of growth conditions on magnetosome chain formation inM. gryphiswaldenseby electron microscopy. Whereas higher temperatures (30 to 35°C) and high oxygen concentrations caused increasingly disordered chains and smaller magnetite crystals, growth at 20°C and anoxic conditions resulted in long chains with mature cuboctahedron-shaped crystals. In order to analyze the magnetosome chain in electron microscopy data sets in a more quantitative and unbiased manner, we developed a computerized image analysis algorithm. The collected data comprised the cell dimensions and particle size and number as well as the intracellular position and extension of the magnetosome chain. The chain analysis program (CHAP) was used to evaluate the effects of the genetic and growth conditions on magnetosome chain formation. This was compared and correlated to data obtained from bulk magnetic measurements of wild-type (WT) and mutant cells displaying different chain configurations. These techniques were used to differentiate mutants due to magnetosome chain defects on a bulk scale.
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Ma, Yong, Fangfang Guo, Yunpeng Zhang, Xiuyu Sun, Tong Wen, and Wei Jiang. "OxyR-Like Improves Cell Hydrogen Peroxide Tolerance by Participating in Monocyte Chemotaxis and Oxidative Phosphorylation Regulation in Magnetospirillum Gryphiswaldense MSR-1." Journal of Biomedical Nanotechnology 17, no. 12 (December 1, 2021): 2466–76. http://dx.doi.org/10.1166/jbn.2021.3205.
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The formation of magnetosomes inside magnetotactic bacteria is a complex process strictly controlled by the intracellular metabolic regulatory system. A series of transcriptional regulators are involved in the biosynthesis of the magnetosome, including OxyR-Like protein, which is indispensable for the maturation of magnetosomes in Magnetospirillum Gryphiswaldense MSR-1. In this study, a new function of the OxyR-Like protein that helps cells resist reactive oxygen species (ROS) was identified. A comparison of expression profile data between wild-type MSR-1 and an oxyR-Like defective mutant demonstrated that seven genes encoding chemotaxis proteins were down-regulated in the latter. On the contrary, the expression levels of numerous genes encoding proteins that are critical for cellular aerobic respiration were up-regulated. Thus, OxyR-Like enhanced the resistance of cells to ROS by increasing their environmental perception and maintaining their oxidative phosphorylation at a reasonable level to avoid the excessive production of endogenous ROS. These results increase our knowledge of the OxyR-Like regulatory network and establish a relationship between the antioxidant metabolic pathway and magnetosome biomineralization in MSR-1.
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Reinholdsson, M., and I. Snowball. "Magnetic quantification of Fe and S bound as magnetosomal greigite in laminated sapropels in deeper basins of the Baltic Sea." Biogeosciences Discussions 11, no. 1 (January 13, 2014): 729–52. http://dx.doi.org/10.5194/bgd-11-729-2014.
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Abstract. Magnetotactic bacteria (MTB) biomineralize magnetite and/or greigite for navigation purposes and it have been suggested that their magnetosomes make a significant contribution to the burial of Fe (and S and O) in sedimentary environments. To test this hypothesis and improve our understanding of MTBs impact on the rate of burial of these two elements we have quantified the abundance of Fe and S bound as greigite magnetofossils in laminated Baltic Sea sapropels, which were formed during periods of hypoxia and anoxia, using mineral magnetic measurements. Fluxes of Fe and S in the form of preserved greigite magnetofossils were calculated for three sedimentary sequences. The magnetosomal Fe (and S) fluxes range between 0.19 and 1.46 × 10−6 g cm−2 yr−1 (0.15 and 1.12 × 10−6 g cm−2 yr−1), and varied in time and space. The contribution of magnetosomal Fe to total Fe fluxes is relatively low, < 0.2%, although its contribution can be important in other stratified waters that suffer from hypoxia/anoxia. We show that the magnetosomal fluxes of Fe in the Baltic Sea are, however, similar to fluxes of Fe derived from mineral magnetic studies of magnetite magnetosomes in organic rich, varved freshwater lake sediments in Sweden.
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Zhang, Shuang, Xinxin Fan, Guojing Zhang, Weidong Wang, and Lei Yan. "Preparation, characterization, and in vitro release kinetics of doxorubicin-loaded magnetosomes." Journal of Biomaterials Applications 36, no. 8 (November 30, 2021): 1469–83. http://dx.doi.org/10.1177/08853282211060544.
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The doxorubicin (DOX) was successfully coupled to the magnetosomes from Acidithiobacillus ferrooxidans ( At. ferrooxidans) by genipin bridging. The parameters (magnetosome concentration, DOX concentration, genipin concentration-, and cross-link time) expected for temperature significantly influenced the coupling rate. Bacterial magnetosome-doxorubicin complexes (BMDCs) were characterized by transmission electron microscope (TEM), particle size analyzer and Fourier transform infrared spectroscopy. Results indicated that BMDCs exhibited a mean particle size of 83.98 mm and displayed a negative charge. The chemical reaction occurring between CO and NH group and the physical adsorption predominated by electrostatic interaction were found to involve in coupling. BMDCs can release 40% of DOX in simulated gastrointestinal conditions within 38 h. Kinetic models including Higuchi, Korsmeyer–Peppas, Zero order, First order, Hixon-Crowell, Baker-Lonsdale, and Weibull and Gompertz were utilized to explore the release mechanism of DOX from BMDCs. All models were found to fit well (r2 ≥ 0.8144) with the release data and the Gompertz was the best fit model (r2 = 0.9742), implying that the complex mechanisms involving Fickian and Gompertz diffusion contributed to the release. These findings suggested that magnetosomes from At. ferrooxidans have great potential applications in biomedical and clinical fields as the carrier of target drug delivery systems in the future.
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Raschdorf, Oliver, Jürgen M. Plitzko, Dirk Schüler, and Frank D. Müller. "A TailoredgalKCounterselection System for Efficient Markerless Gene Deletion and Chromosomal Tagging in Magnetospirillum gryphiswaldense." Applied and Environmental Microbiology 80, no. 14 (May 9, 2014): 4323–30. http://dx.doi.org/10.1128/aem.00588-14.
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ABSTRACTMagnetotactic bacteria have emerged as excellent model systems to study bacterial cell biology, biomineralization, vesicle formation, and protein targeting because of their ability to synthesize single-domain magnetite crystals within unique organelles (magnetosomes). However, only few species are amenable to genetic manipulation, and the limited methods for site-specific mutagenesis are tedious and time-consuming. Here, we report the adaptation and application of a fast and convenient technique for markerless chromosomal manipulation ofMagnetospirillum gryphiswaldenseusing a single antibiotic resistance cassette andgalK-based counterselection for marker recycling. We demonstrate the potential of this technique by genomic excision of thephbCABoperon, encoding enzymes for polyhydroxyalkanoate (PHA) synthesis, followed by chromosomal fusion of magnetosome-associated proteins to fluorescent proteins. Because of the absence of interfering PHA particles, these engineered strains are particularly suitable for microscopic analyses of cell biology and magnetosome biosynthesis.
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Taylor, A. P., and J. C. Barry. "Magnetosomal matrix: ultrafine structure may template biomineralization of magnetosomes." Journal of Microscopy 213, no. 2 (January 22, 2004): 180–97. http://dx.doi.org/10.1111/j.1365-2818.2004.01287.x.
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Baaziz, Walid, Corneliu Ghica, Jefferson Cypriano, Fernanda Abreu, Karine Anselme, Ovidiu Ersen, Marcos Farina, and Jacques Werckmann. "New Phenotype and Mineralization of Biogenic Iron Oxide in Magnetotactic Bacteria." Nanomaterials 11, no. 12 (November 25, 2021): 3189. http://dx.doi.org/10.3390/nano11123189.
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Many magnetotactic bacteria (MTB) biomineralize magnetite crystals that nucleate and grow inside intracellular membranous vesicles originating from invaginations of the cytoplasmic membrane. The crystals together with their surrounding membranes are referred to as magnetosomes. Magnetosome magnetite crystals nucleate and grow using iron transported inside the vesicle by specific proteins. Here, we tackle the question of the organization of magnetosomes, which are always described as constituted by linear chains of nanocrystals. In addition, it is commonly accepted that the iron oxide nanocrystals are in the magnetite-based phase. We show, in the case of a wild species of coccus-type bacterium, that there is a double organization of the magnetosomes, relatively perpendicular to each other, and that the nanocrystals are in fact maghemite. These findings were obtained, respectively, by using electron tomography of whole mounts of cells directly from the environment and high-resolution transmission electron microscopy and diffraction. Structure simulations were performed with the MacTempas software. This study opens new perspectives on the diversity of phenotypes within MTBs and allows to envisage other mechanisms of nucleation and formation of biogenic iron oxide crystals.
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Schultheiss, Daniel, René Handrick, Dieter Jendrossek, Marianne Hanzlik, and Dirk Schüler. "The Presumptive Magnetosome Protein Mms16 Is a Poly(3-Hydroxybutyrate) Granule-Bound Protein (Phasin) in Magnetospirillum gryphiswaldense." Journal of Bacteriology 187, no. 7 (April 1, 2005): 2416–25. http://dx.doi.org/10.1128/jb.187.7.2416-2425.2005.
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ABSTRACT The Mms16 protein has been previously found to be associated with isolated magnetosomes from two Magnetospirillum strains. A function of this protein as a magnetosome-specific GTPase involved in the formation of intracellular magnetosome membrane vesicles was suggested (Y. Okamura, H. Takeyama, and T. Matsunaga, J. Biol. Chem. 276:48183-48188, 2001). Here we present a study of the Mms16 protein from Magnetospirillum gryphiswaldense to clarify its function. Insertion-duplication mutagenesis of the mms16 gene did not affect the formation of magnetosome particles but resulted in the loss of the ability of M. gryphiswaldense cell extracts to activate poly(3-hydroxybutyrate) (PHB) depolymerization in vitro, which was coincident with loss of the most abundant 16-kDa polypeptide from preparations of PHB granule-bound proteins. The mms16 mutation could be functionally complemented by enhanced yellow fluorescent protein (EYFP) fused to ApdA, which is a PHB granule-bound protein (phasin) in Rhodospirillum rubrum sharing 55% identity to Mms16. Fusions of Mms16 and ApdA to enhanced green fluorescent protein (EGFP) or EYFP were colocalized in vivo with the PHB granules but not with the magnetosome particles after conjugative transfer to M. gryphiswaldense. Although the Mms16-EGFP fusion protein became detectable by Western analysis in all cell fractions upon cell disruption, it was predominantly associated with isolated PHB granules. Contrary to previous suggestions, our results argue against an essential role of Mms16 in magnetosome formation, and the previously observed magnetosome localization is likely an artifact due to unspecific adsorption during preparation. Instead, we conclude that Mms16 in vivo is a PHB granule-bound protein (phasin) and acts in vitro as an activator of PHB hydrolysis by R. rubrum PHB depolymerase PhaZ1. Accordingly, we suggest renaming the Mms16 protein of Magnetospirillum species to ApdA, as in R. rubrum.
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Siponen, Marina I., Géraldine Adryanczyk, Nicolas Ginet, Pascal Arnoux, and David Pignol. "Magnetochrome: a c-type cytochrome domain specific to magnetotatic bacteria." Biochemical Society Transactions 40, no. 6 (November 21, 2012): 1319–23. http://dx.doi.org/10.1042/bst20120104.
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Magnetotactic bacteria consist of a group of taxonomically, physiologically and morphologically diverse prokaryotes, with the singular ability to align with geomagnetic field lines, a phenomenon referred to as magnetotaxis. This magnetotactic property is due to the presence of iron-rich crystals embedded in lipidic vesicles forming an organelle called the magnetosome. Magnetosomes are composed of single-magnetic-domain nanocrystals of magnetite (Fe3O4) or greigite (Fe3S4) embedded in biological membranes, thereby forming a prokaryotic organelle. Four specific steps are described in this organelle formation: (i) membrane specialization, (ii) iron acquisition, (iii) magnetite (or greigite) biocrystallization, and (iv) magnetosome alignment. The formation of these magnetic crystals is a genetically controlled process, which is governed by enzyme-catalysed processes. On the basis of protein sequence analysis of genes known to be involved in magnetosome formation in Magnetospirillum magneticum AMB-1, we have identified a subset of three membrane-associated or periplasmic proteins containing a double cytochrome c signature motif CXXCH: MamE, MamP and MamT. The presence of these proteins suggests the existence of an electron-transport chain inside the magnetosome, contributing to the process of biocrystallization. We have performed heterologous expression in E. coli of the cytochrome c motif-containing domains of MamE, MamP and MamT. Initial biophysical characterization has confirmed that MamE, MamP and MamT are indeed c-type cytochromes. Furthermore, determination of redox potentials for this new family of c-type cytochromes reveals midpoint potentials of −76 and −32 mV for MamP and MamE respectively.
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Taher, Zainab, Christopher Legge, Natalie Winder, Pawel Lysyganicz, Andrea Rawlings, Helen Bryant, Munitta Muthana, and Sarah Staniland. "Magnetosomes and Magnetosome Mimics: Preparation, Cancer Cell Uptake and Functionalization for Future Cancer Therapies." Pharmaceutics 13, no. 3 (March 10, 2021): 367. http://dx.doi.org/10.3390/pharmaceutics13030367.
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Magnetic magnetite nanoparticles (MNP) are heralded as model vehicles for nanomedicine, particularly cancer therapeutics. However, there are many methods of synthesizing different sized and coated MNP, which may affect their performance as nanomedicines. Magnetosomes are naturally occurring, lipid-coated MNP that exhibit exceptional hyperthermic heating, but their properties, cancer cell uptake and toxicity have yet to be compared to other MNP. Magnetosomes can be mimicked by coating MNP in either amphiphilic oleic acid or silica. In this study, magnetosomes are directly compared to control MNP, biomimetic oleic acid and silica coated MNP of varying sizes. MNP are characterized and compared with respect to size, magnetism, and surface properties. Small (8 ± 1.6 nm) and larger (32 ± 9.9 nm) MNP are produced by two different methods and coated with either silica or oleic acid, increasing the size and the size dispersity of the MNP. The coated larger MNP are comparable in size (49 ± 12.5 nm and 61 ± 18.2 nm) to magnetosomes (46 ± 11.8 nm) making good magnetosome mimics. All MNP are assessed and compared for cancer cell uptake in MDA-MB-231 cells and importantly, all are readily taken up with minimal toxic effect. Silica coated MNP show the most uptake with greater than 60% cell uptake at the highest concentration, and magnetosomes showing the least with less than 40% at the highest concentration, while size does not have a significant effect on uptake. Finally, surface functionalization is demonstrated for magnetosomes and silica coated MNP using biotinylation and EDC-NHS, respectively, to conjugate fluorescent probes. The modified particles are visualized in MDA-MB-231 cells and demonstrate how both naturally biosynthesized magnetosomes and biomimetic silica coated MNP can be functionalized and readily up taken by cancer cells for realization as nanomedical vehicles.
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Wang, Xiaoke, Likun Liang, Tao Song, and Longfei Wu. "Sinusoidal magnetic field stimulates magnetosome formation and affects mamA, mms13, mms6, and magA expression in Magnetospirillum magneticum AMB-1." Canadian Journal of Microbiology 54, no. 12 (December 2008): 1016–22. http://dx.doi.org/10.1139/w08-095.
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Magnetic particles are currently one of the most important materials in the industrial sector, where they have been widely used for biotechnological and biomedical applications. To investigate the effects of the imposed magnetic field on biomineralization in Magnetospirillum magneticum AMB-1 and to suggest a new approach that enhances formation of magnetosomes, cultures inoculated with either magnetic or nonmagnetic precultures were incubated under a sinusoidal magnetic field or geomagnetic field. The results showed that the sinusoidal magnetic field up-regulated mms6 expression in the cultures inoculated with magnetic cells, and magA, mms6, and mamA expression in the cultures inoculated with nonmagnetic cells. The applied sinusoidal magnetic field could block cell division, which could contribute to a decrease in the OD600 values and an increase in the coefficient of magnetism values of the cultures, which could mean that the percentage of mature magnetosome-containing bacteria was increased. The linearity of magnetosome chains was affected, but the number of magnetic particles in cells was increased when a sinusoidal magnetic field was applied to the cultures. The results imply that the variable intensity and orientation of the sinusoidal magnetic field resulted in magnetic pole conversion in the newly forming magnetic particles, which could affect the formation of magnetic crystals and the arrangement of the adjacent magnetosome.
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Taoka, Azuma, Junya Kondo, Zachery Oestreicher, and Yoshihiro Fukumori. "Characterization of uncultured giant rod-shaped magnetotactic Gammaproteobacteria from a freshwater pond in Kanazawa, Japan." Microbiology 160, no. 10 (October 1, 2014): 2226–34. http://dx.doi.org/10.1099/mic.0.078717-0.
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Magnetotactic bacteria (MTB) are widespread aquatic bacteria, and are a phylogenetically, physiologically and morphologically heterogeneous group, but they all have the ability to orientate and move along the geomagnetic field using intracellular magnetic organelles called magnetosomes. Isolation and cultivation of novel MTB are necessary for a comprehensive understanding of magnetosome formation and function in divergent MTB. In this study, we enriched a giant rod-shaped magnetotactic bacterium (strain GRS-1) from a freshwater pond in Kanazawa, Japan. Cells of strain GRS-1 were unusually large (~13×~8 µm). They swam in a helical trajectory towards the south pole of a bar magnet by means of a polar bundle of flagella. Another striking feature of GRS-1 was the presence of two distinct intracellular biomineralized structures: large electron-dense granules composed of calcium and long chains of magnetosomes that surround the large calcium granules. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that this strain belongs to the Gammaproteobacteria and represents a new genus of MTB.
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Grünberg, Karen, Eva-Christina Müller, Albrecht Otto, Regina Reszka, Dietmar Linder, Michael Kube, Richard Reinhardt, and Dirk Schüler. "Biochemical and Proteomic Analysis of the Magnetosome Membrane in Magnetospirillum gryphiswaldense." Applied and Environmental Microbiology 70, no. 2 (February 2004): 1040–50. http://dx.doi.org/10.1128/aem.70.2.1040-1050.2004.
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ABSTRACT We analyzed the biochemical composition of the magnetosome membrane (MM) in Magnetospirillum gryphiswaldense. Isolated magnetosomes were associated with phospholipids and fatty acids which were similar to phospholipids and fatty acids from other subcellular compartments (i.e., outer and cytoplasmic membranes) but were present in different proportions. The binding characteristics of MM-associated proteins were studied by selective solubilization and limited proteolysis. The MM-associated proteins were further analyzed by various proteomic approaches, including one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Edman and mass spectrometric (electrospray ionization-mass spectrometry-mass spectrometry) sequencing, as well as capillary liquid chromatography-mass spectrometry-mass spectrometry of total tryptic digests of the MM. At least 18 proteins were found to constitute the magnetosome subproteome, and most of these proteins are novel for M. gryphiswaldense. Except for MM22 and Mms16, all bona fide MM proteins (MMPs) were encoded by open reading frames in the mamAB, mamDC, and mms6 clusters in the previously identified putative magnetosome island. Eight of the MMPs display homology to known families, and some of them occur in the MM in multiple homologues. Ten of the MMPs have no known homologues in nonmagnetic organisms and thus represent novel, magnetotactic bacterium-specific protein families. Several MMPs display repetitive or highly acidic sequence patterns, which are known from other biomineralizing systems and thus may have relevance for magnetite formation.
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Lin, Wei, and Yongxin Pan. "Uncultivated Magnetotactic Cocci from Yuandadu Park in Beijing, China." Applied and Environmental Microbiology 75, no. 12 (April 17, 2009): 4046–52. http://dx.doi.org/10.1128/aem.00247-09.
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ABSTRACT In the present study, we investigated a group of uncultivated magnetotactic cocci, which was magnetically isolated from a freshwater pond in Beijing, China. Light and transmission electron microscopy showed that these cocci ranged from 1.5 to 2.5 μm and contained two to four chains of magnetite magnetosomes, which sometimes were partially disorganized. Overall, the size of the disorganized magnetosomes was significantly smaller than that arranged in chains. All characterized magnetosome crystals were elongated (shape factor = 0.64) and fall into the single-domain size range (30 to 115 nm). Comparative 16S rRNA gene sequence analysis and fluorescence in situ hybridization showed that the enriched bacteria were a virtually homogeneous population and represented a novel lineage in the Alphaproteobacteria. The closest cultivated relative was magnetotactic coccoid strain MC-1 (88% sequence identity). First-order reversal curve diagrams revealed that these cocci had relatively strong magnetic interactions compared to the single-chain magnetotactic bacteria. Low-temperature magnetic measurements showed that the Verwey transition of them was ∼108 K, confirming magnetite magnetosomes, and the delta ratio δFC/δZFC was >2. Based on the structure, phylogenetic position and magnetic properties, the enriched magnetotactic cocci of Alphaproteobacteria are provisionally named as “Candidatus Magnetococcus yuandaducum.”
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Scheffel, André, and Dirk Schüler. "The Acidic Repetitive Domain of the Magnetospirillum gryphiswaldense MamJ Protein Displays Hypervariability but Is Not Required for Magnetosome Chain Assembly." Journal of Bacteriology 189, no. 17 (June 29, 2007): 6437–46. http://dx.doi.org/10.1128/jb.00421-07.
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ABSTRACT Magnetotactic bacteria navigate along the earth's magnetic field using chains of magnetosomes, which are intracellular organelles comprising membrane-enclosed magnetite crystals. The assembly of highly ordered magnetosome chains is under genetic control and involves several specific proteins. Based on genetic and cryo-electron tomography studies, a model was recently proposed in which the acidic MamJ magnetosome protein attaches magnetosome vesicles to the actin-like cytoskeletal filament formed by MamK, thereby preventing magnetosome chains from collapsing. However, the exact functions as well as the mode of interaction between MamK and MamJ are unknown. Here, we demonstrate that several functional MamJ variants from Magnetospirillum gryphiswaldense and other magnetotactic bacteria share an acidic and repetitive central domain, which displays an unusual intra- and interspecies sequence polymorphism, probably caused by homologous recombination between identical copies of Glu- and Pro-rich repeats. Surprisingly, mamJ mutant alleles in which the central domain was deleted retained their potential to restore chain formation in a ΔmamJ mutant, suggesting that the acidic domain is not essential for MamJ's function. Results of two-hybrid experiments indicate that MamJ physically interacts with MamK, and two distinct sequence regions within MamJ were shown to be involved in binding to MamK. Mutant variants of MamJ lacking either of the binding domains were unable to functionally complement the ΔmamJ mutant. In addition, two-hybrid experiments suggest both MamK-binding domains of MamJ confer oligomerization of MamJ. In summary, our data reveal domains required for the functions of the MamJ protein in chain assembly and maintenance and provide the first experimental indications for a direct interaction between MamJ and the cytoskeletal filament protein MamK.
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Richter, Michael, Michael Kube, Dennis A. Bazylinski, Thierry Lombardot, Frank Oliver Glöckner, Richard Reinhardt, and Dirk Schüler. "Comparative Genome Analysis of Four Magnetotactic Bacteria Reveals a Complex Set of Group-Specific Genes Implicated in Magnetosome Biomineralization and Function." Journal of Bacteriology 189, no. 13 (April 20, 2007): 4899–910. http://dx.doi.org/10.1128/jb.00119-07.
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ABSTRACT Magnetotactic bacteria (MTB) are a heterogeneous group of aquatic prokaryotes with a unique intracellular organelle, the magnetosome, which orients the cell along magnetic field lines. Magnetotaxis is a complex phenotype, which depends on the coordinate synthesis of magnetosomes and the ability to swim and orient along the direction caused by the interaction with the Earth's magnetic field. Although a number of putative magnetotaxis genes were recently identified within a conserved genomic magnetosome island (MAI) of several MTB, their functions have remained mostly unknown, and it was speculated that additional genes located outside the MAI might be involved in magnetosome formation and magnetotaxis. In order to identify genes specifically associated with the magnetotactic phenotype, we conducted comparisons between four sequenced magnetotactic Alphaproteobacteria including the nearly complete genome of Magnetospirillum gryphiswaldense strain MSR-1, the complete genome of Magnetospirillum magneticum strain AMB-1, the complete genome of the magnetic coccus MC-1, and the comparative-ready preliminary genome assembly of Magnetospirillum magnetotacticum strain MS-1 against an in-house database comprising 426 complete bacterial and archaeal genome sequences. A magnetobacterial core genome of about 891 genes was found shared by all four MTB. In addition to a set of approximately 152 genus-specific genes shared by the three Magnetospirillum strains, we identified 28 genes as group specific, i.e., which occur in all four analyzed MTB but exhibit no (MTB-specific genes) or only remote (MTB-related genes) similarity to any genes from nonmagnetotactic organisms and which besides various novel genes include nearly all mam and mms genes previously shown to control magnetosome formation. The MTB-specific and MTB-related genes to a large extent display synteny, partially encode previously unrecognized magnetosome membrane proteins, and are either located within (18 genes) or outside (10 genes) the MAI of M. gryphiswaldense. These genes, which represent less than 1% of the 4,268 open reading frames of the MSR-1 genome, as yet are mostly of unknown functions but are likely to be specifically involved in magnetotaxis and, thus, represent prime targets for future experimental analysis.
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Bennet, Mathieu, Luca Bertinetti, Robert K. Neely, Andreas Schertel, André Körnig, Cristina Flors, Frank D. Müller, Dirk Schüler, Stefan Klumpp, and Damien Faivre. "Biologically controlled synthesis and assembly of magnetite nanoparticles." Faraday Discussions 181 (2015): 71–83. http://dx.doi.org/10.1039/c4fd00240g.
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Magnetite nanoparticles have size- and shape-dependent magnetic properties. In addition, assemblies of magnetite nanoparticles forming one-dimensional nanostructures have magnetic properties distinct from zero-dimensional or non-organized materials due to strong uniaxial shape anisotropy. However, assemblies of free-standing magnetic nanoparticles tend to collapse and form closed-ring structures rather than chains in order to minimize their energy. Magnetotactic bacteria, ubiquitous microorganisms, have the capability to mineralize magnetite nanoparticles, the so-called magnetosomes, and to direct their assembly in stable chainsviabiological macromolecules. In this contribution, the synthesis and assembly of biological magnetite to obtain functional magnetic dipoles in magnetotactic bacteria are presented, with a focus on the assembly. We present tomographic reconstructions based on cryo-FIB sectioning and SEM imaging of a magnetotactic bacterium to exemplify that the magnetosome chain is indeed a paradigm of a 1D magnetic nanostructure, based on the assembly of several individual particles. We show that the biological forces are a major player in the formation of the magnetosome chain. Finally, we demonstrate by super resolution fluorescence microscopy that MamK, a protein of the actin family necessary to form the chain backbone in the bacteria, forms a bundle of filaments that are not only found in the vicinity of the magnetosome chain but are widespread within the cytoplasm, illustrating the dynamic localization of the protein within the cells. These very simple microorganisms have thus much to teach us with regards to controlling the design of functional 1D magnetic nanoassembly.
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Scheffel, André, Astrid Gärdes, Karen Grünberg, Gerhard Wanner, and Dirk Schüler. "The Major Magnetosome Proteins MamGFDC Are Not Essential for Magnetite Biomineralization in Magnetospirillum gryphiswaldense but Regulate the Size of Magnetosome Crystals." Journal of Bacteriology 190, no. 1 (October 26, 2007): 377–86. http://dx.doi.org/10.1128/jb.01371-07.
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ABSTRACT Magnetospirillum gryphiswaldense and related magnetotactic bacteria form magnetosomes, which are membrane-enclosed organelles containing crystals of magnetite (Fe3O4) that cause the cells to orient in magnetic fields. The characteristic sizes, morphologies, and patterns of alignment of magnetite crystals are controlled by vesicles formed of the magnetosome membrane (MM), which contains a number of specific proteins whose precise roles in magnetosome formation have remained largely elusive. Here, we report on a functional analysis of the small hydrophobic MamGFDC proteins, which altogether account for nearly 35% of all proteins associated with the MM. Although their high levels of abundance and conservation among magnetotactic bacteria had suggested a major role in magnetosome formation, we found that the MamGFDC proteins are not essential for biomineralization, as the deletion of neither mamC, encoding the most abundant magnetosome protein, nor the entire mamGFDC operon abolished the formation of magnetite crystals. However, cells lacking mamGFDC produced crystals that were only 75% of the wild-type size and were less regular than wild-type crystals with respect to morphology and chain-like organization. The inhibition of crystal formation could not be eliminated by increased iron concentrations. The growth of mutant crystals apparently was not spatially constrained by the sizes of MM vesicles, as cells lacking mamGFDC formed vesicles with sizes and shapes nearly identical to those formed by wild-type cells. However, the formation of wild-type-size magnetite crystals could be gradually restored by in-trans complementation with one, two, and three genes of the mamGFDC operon, regardless of the combination, whereas the expression of all four genes resulted in crystals exceeding the wild-type size. Our data suggest that the MamGFDC proteins have partially redundant functions and, in a cumulative manner, control the growth of magnetite crystals by an as-yet-unknown mechanism.
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Schultheiss, Daniel, Michael Kube, and Dirk Sch�ler. "Inactivation of the Flagellin Gene flaA in Magnetospirillum gryphiswaldense Results in Nonmagnetotactic Mutants Lacking Flagellar Filaments." Applied and Environmental Microbiology 70, no. 6 (June 2004): 3624–31. http://dx.doi.org/10.1128/aem.70.6.3624-3631.2004.
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ABSTRACT Magnetotactic bacteria synthesize magnetosomes, which cause them to orient and migrate along magnetic field lines. The analysis of magnetotaxis and magnetosome biomineralization at the molecular level has been hindered by the unavailability of genetic methods, namely the lack of a means to introduce directed gene-specific mutations. Here we report a method for knockout mutagenesis by homologous recombination in Magnetospirillum gryphiswaldense. Multiple flagellin genes, which are unlinked in the genome, were identified in M. gryphiswaldense. The targeted disruption of the flagellin gene flaA was shown to eliminate flagella formation, motility, and magnetotaxis. The techniques described in this paper will make it possible to take full advantage of the forthcoming genome sequences of M. gryphiswaldense and other magnetotactic bacteria.
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Staniland, Sarah S., and Andrea E. Rawlings. "Crystallizing the function of the magnetosome membrane mineralization protein Mms6." Biochemical Society Transactions 44, no. 3 (June 9, 2016): 883–90. http://dx.doi.org/10.1042/bst20160057.
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The literature on the magnetosome membrane (MM) protein, magnetosome membrane specific6 (Mms6), is reviewed. Mms6 is native to magnetotactic bacteria (MTB). These bacteria take up iron from solution and biomineralize magnetite nanoparticles within organelles called magnetosomes. Mms6 is a small protein embedded on the interior of the MM and was discovered tightly associated with the formed mineral. It has been the subject of intensive research as it is seen to control the formation of particles both in vivo and in vitro. Here, we compile, review and discuss the research detailing Mms6’s activity within the cell and in a range of chemical in vitro methods where Mms6 has a marked effect on the composition, size and distribution of synthetic particles, with approximately 21 nm in size for solution precipitations and approximately 90 nm for those formed on surfaces. Furthermore, we review and discuss recent work detailing the structure and function of Mms6. From the evidence, we propose a mechanism for its function as a specific magnetite nucleation protein and summaries the key features for this action: namely, self-assembly to display a charged surface for specific iron binding, with the curvature of the surfaces determining the particle size. We suggest these may aid design of biomimetic additives for future green nanoparticle production.
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Ionescu, A., N. J. Darton, K. Vyas, and J. Llandro. "Detection of endogenous magnetic nanoparticles with a tunnelling magneto resistance sensor." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, no. 1927 (September 28, 2010): 4371–87. http://dx.doi.org/10.1098/rsta.2010.0137.
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The magnetotactic bacterium Magnetospirillum sp. has been cultured and the properties of its endogenous magnetic nanoparticles characterized. Electron-microscopic analyses indicate that the endogenous magnetite nanoparticles in Magnetospirillum sp. are coated with a 3–4 nm thick transparent shell, forming a magnetosome. These magnetite nanoparticles had diameters of 50.9±13.3 nm, in good agreement with the diameter of 40.6±1.2 nm extracted from magnetometry. Each Magnetospirillum sp. bacterium contained chains of 5–25 magnetosomes. Superconducting quantum interference device magnetometry results indicate that the extrinsic superparamagnetic response of the bacterial solution at room temperature can be attributed to the reversal of the magnetization by physical rotation of the nanoparticles. The intrinsic blocking temperature of a sample of freeze-dried bacteria was estimated to be 282±13 K. A tunnelling magneto resistance sensor was used to detect the stray fields of endogenous magnetic nanoparticles in static and quasi-dynamic modes. Based on the tunnelling magneto resistance sensor results, the magnetic moment per bacterium was estimated to be approximately 2.6×10 −13 emu. The feasibility of this detection method either as a mass-coverage device or as part of an integrated microfluidic circuit for detection and sorting of magnetosome-containing cells was demonstrated.
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Puri, Ritika, Vimal Arora, Atul Kabra, Harish Dureja, and Shailendra Hamaal. "Magnetosomes: A Tool for Targeted Drug Delivery in the Management of Cancer." Journal of Nanomaterials 2022 (April 30, 2022): 1–12. http://dx.doi.org/10.1155/2022/6414585.
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The last two decades of developments in drug formulations and novel drug delivery systems have been seen as the beginning of a new era leading to increased patient adherence and pharmacological response to the therapeutic regimen. One of the most difficult tasks is efficiency and target-specific drug delivery or the extent of delivery at any given site of interest. Many currently designed drug delivery systems are precisely tailored to maximize the delivery of a particular form of drug by reducing the degradation or loss of the drug. In case of cancer treatment, the targeted drug delivery is of utmost importance as the anticancer agents are not having the ability to differentiate between healthy and tumor cells resulting in adverse effects and/or systemic toxicity. The targeted drug delivery is thus designed to focus on preventing side effects and encouraging the accumulation of the drug at the targeted site; one such promising drug delivery system is magnetosome drug delivery, i.e., drug delivery using magnetosomes (biological magnetic nanoparticles). In this article, we have summarized the system for design, development, and mode of drug delivery using magnetosomes along with the recent developments made in this field to facilitate the diagnosis and treatment of cancer.
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Lin, Wei, Greig A. Paterson, Qiyun Zhu, Yinzhao Wang, Evguenia Kopylova, Ying Li, Rob Knight, et al. "Origin of microbial biomineralization and magnetotaxis during the Archean." Proceedings of the National Academy of Sciences 114, no. 9 (February 13, 2017): 2171–76. http://dx.doi.org/10.1073/pnas.1614654114.
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Microbes that synthesize minerals, a process known as microbial biomineralization, contributed substantially to the evolution of current planetary environments through numerous important geochemical processes. Despite its geological significance, the origin and evolution of microbial biomineralization remain poorly understood. Through combined metagenomic and phylogenetic analyses of deep-branching magnetotactic bacteria from theNitrospiraephylum, and using a Bayesian molecular clock-dating method, we show here that the gene cluster responsible for biomineralization of magnetosomes, and the arrangement of magnetosome chain(s) within cells, both originated before or near the Archean divergence between theNitrospiraeandProteobacteria. This phylogenetic divergence occurred well before the Great Oxygenation Event. Magnetotaxis likely evolved due to environmental pressures conferring an evolutionary advantage to navigation via the geomagnetic field. Earth’s dynamo must therefore have been sufficiently strong to sustain microbial magnetotaxis in the Archean, suggesting that magnetotaxis coevolved with the geodynamo over geological time.
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Bury, Peter, Marek Veveričík, František Černobila, Matúš Molčan, Katarína Zakuťanská, Peter Kopčanský, and Milan Timko. "Effect of Liquid Crystalline Host on Structural Changes in Magnetosomes Based Ferronematics." Nanomaterials 11, no. 10 (October 8, 2021): 2643. http://dx.doi.org/10.3390/nano11102643.
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The effect of the liquid crystalline host on structural changes in magnetosomes based on ferronematics is studied using the surface acoustic wave (SAW) technique supported by some capacitance and light transmission measurements. The measurement of the attenuation response of SAW propagating along the interface between LC and the piezoelectric substrate is used to study processes of structural changes under magnetic field. The magnetosome nanoparticles of the same volume concentration were added to three different nematic LCs, 5CB, 6CB, and E7. Unlike to undoped LCs, the different responses of SAW attenuation under the influence of magnetic and electric fields in LCs doped with magnetosomes were observed due to characteristic structural changes. The decrease of the threshold field for doped LCs as compared with pure LCs and slight effects on structural changes were registered. The threshold magnetic fields of LCs and composites were determined from capacitance measurements, and the slight shift to lower values was registered for doped LCs. The shift of nematic-isotropic transition was registered from dependencies of SAW attenuation on temperature. The acoustic anisotropy measurement approved the previous supposition about the role of bulk viscosity in used SAW measurements. In addition, capacitance and light transmition investigations supported SAW results and pointed out conclusions about their magnetic field behavior. Obtained results are discussed and confronted with previous ones and coincide well with those observed using acoustic, optical, or dielectric techniques.
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Abreu, Fernanda, Karen Tavares Silva, Pedro Leão, Iame Alves Guedes, Carolina Neumann Keim, Marcos Farina, and Ulysses Lins. "Cell Adhesion, Multicellular Morphology, and Magnetosome Distribution in the Multicellular Magnetotactic Prokaryote Candidatus Magnetoglobus multicellularis." Microscopy and Microanalysis 19, no. 3 (April 3, 2013): 535–43. http://dx.doi.org/10.1017/s1431927613000329.
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AbstractCandidatus Magnetoglobus multicellularis is an uncultured magnetotactic multicellular prokaryote composed of 17-40 Gram-negative cells that are capable of synthesizing organelles known as magnetosomes. The magnetosomes of Ca. M. multicellularis are composed of greigite and are organized in chains that are responsible for the microorganism's orientation along magnetic field lines. The characteristics of the microorganism, including its multicellular life cycle, magnetic field orientation, and swimming behavior, and the lack of viability of individual cells detached from the whole assembly, are considered strong evidence for the existence of a unique multicellular life cycle among prokaryotes. It has been proposed that the position of each cell within the aggregate is fundamental for the maintenance of its distinctive morphology and magnetic field orientation. However, the cellular organization of the whole organism has never been studied in detail. Here, we investigated the magnetosome organization within a cell, its distribution within the microorganism, and the intercellular relationships that might be responsible for maintaining the cells in the proper position within the microorganism, which is essential for determining the magnetic properties of Ca. M. multicellularis during its life cycle. The results indicate that cellular interactions are essential for the determination of individual cell shape and the magnetic properties of the organism and are likely directly associated with the morphological changes that occur during the multicellular life cycle of this species.
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Lefèvre, Christopher T., Tao Song, Jean-Paul Yonnet, and Long-Fei Wu. "Characterization of Bacterial Magnetotactic Behaviors by Using a Magnetospectrophotometry Assay." Applied and Environmental Microbiology 75, no. 12 (April 17, 2009): 3835–41. http://dx.doi.org/10.1128/aem.00165-09.
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ABSTRACT Magnetotactic bacteria have the unique capacity of synthesizing intracellular single-domain magnetic particles called magnetosomes. The magnetosomes are usually organized in a chain that allows the bacteria to align and swim along geomagnetic field lines, a behavior called magnetotaxis. Two mechanisms of magnetotaxis have been described. Axial magnetotactic cells swim in both directions along magnetic field lines. In contrast, polar magnetotactic cells swim either parallel to the geomagnetic field lines toward the North Pole (north seeking) or antiparallel toward the South Pole (south seeking). In this study, we used a magnetospectrophotometry (MSP) assay to characterize both the axial magnetotaxis of “Magnetospirillum magneticum” strain AMB-1 and the polar magnetotaxis of magneto-ovoid strain MO-1. Two pairs of Helmholtz coils were mounted onto the cuvette holder of a common laboratory spectrophotometer to generate two mutually perpendicular homogeneous magnetic fields parallel or perpendicular to the light beam. The application of magnetic fields allowed measurements of the change in light scattering resulting from cell alignment in a magnetic field or in absorbance due to bacteria swimming across the light beam. Our results showed that MSP is a powerful tool for the determination of bacterial magnetism and the analysis of alignment and swimming of magnetotactic bacteria in magnetic fields. Moreover, this assay allowed us to characterize south-seeking derivatives and non-magnetosome-bearing strains obtained from north-seeking MO-1 cultures. Our results suggest that oxygen is a determinant factor that controls magnetotactic behavior.
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Wang, Qing, Meiwen Wang, Xu Wang, Guohua Guan, Ying Li, Youliang Peng, and Jilun Li. "Iron Response Regulator Protein IrrB in Magnetospirillum gryphiswaldense MSR-1 Helps Control the Iron/Oxygen Balance, Oxidative Stress Tolerance, and Magnetosome Formation." Applied and Environmental Microbiology 81, no. 23 (September 18, 2015): 8044–53. http://dx.doi.org/10.1128/aem.02585-15.
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ABSTRACTMagnetotactic bacteria are capable of forming nanosized, membrane-enclosed magnetosomes under iron-rich and oxygen-limited conditions. The complete genomic sequence ofMagnetospirillum gryphiswaldensestrain MSR-1 has been analyzed and found to contain fivefurhomologue genes whose protein products are predicted to be involved in iron homeostasis and the response to oxidative stress. Of these, only the MGMSRv2_3149 gene (irrB) was significantly downregulated under high-iron and low-oxygen conditions, during the transition of cell growth from the logarithmic to the stationary phase. The encoded protein, IrrB, containing the conserved HHH motif, was identified as an iron response regulator (Irr) protein belonging to the Fur superfamily. To investigate the function of IrrB, we constructed anirrBdeletion mutant (ΔirrB). The levels of cell growth and magnetosome formation were lower in the ΔirrBstrain than in the wild type (WT) under both high-iron and low-iron conditions. The ΔirrBstrain also showed lower levels of iron uptake and H2O2tolerance than the WT. Quantitative real-time reverse transcription-PCR analysis indicated that theirrBmutation reduced the expression of numerous genes involved in iron transport, iron storage, heme biosynthesis, and Fe-S cluster assembly. Transcription studies of the otherfurhomologue genes in the ΔirrBstrain indicated complementary functions of the Fur proteins in MSR-1. IrrB appears to be directly responsible for iron metabolism and homeostasis and to be indirectly involved in magnetosome formation. We propose two IrrB-regulated networks (under high- and low-iron conditions) in MSR-1 cells that control the balance of iron and oxygen metabolism and account for the coexistence of five Fur homologues.
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Usov, Nikolai A., and Elizaveta M. Gubanova. "Application of Magnetosomes in Magnetic Hyperthermia." Nanomaterials 10, no. 7 (July 5, 2020): 1320. http://dx.doi.org/10.3390/nano10071320.
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Nanoparticles, specifically magnetosomes, synthesized in nature by magnetotactic bacteria, are very promising to be usedin magnetic hyperthermia in cancer treatment. In this work, using the solution of the stochastic Landau–Lifshitz equation, we calculate the specific absorption rate (SAR) in an alternating (AC) magnetic field of assemblies of magnetosome chains depending on the particle size D, the distance between particles in a chain a, and the angle of the applied magnetic field with respect to the chain axis. The dependence of SAR on the a/D ratio is shown to have a bell-shaped form with a pronounced maximum. For a dilute oriented chain assembly with optimally chosen a/D ratio, a strong magneto-dipole interaction between the chain particles leads to an almost rectangular hysteresis loop, and to large SAR values in the order of 400–450 W/g at moderate frequencies f = 300 kHz and small magnetic field amplitudes H0 = 50–100 Oe. The maximum SAR value only weakly depends on the diameter of the nanoparticles and the length of the chain. However, a significant decrease in SAR occurs in a dense chain assembly due to the strong magneto-dipole interaction of nanoparticles of different chains.
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Shimoshige, Hirokazu, Hideki Kobayashi, Shigeru Shimamura, Toru Mizuki, Akira Inoue, and Toru Maekawa. "Isolation and cultivation of a novel sulfate-reducing magnetotactic bacterium belonging to the genus Desulfovibrio." PLOS ONE 16, no. 3 (March 11, 2021): e0248313. http://dx.doi.org/10.1371/journal.pone.0248313.
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Magnetotactic bacteria (MTB) synthesize magnetosomes composed of membrane-enveloped magnetite (Fe3O4) and/or greigite (Fe3S4) nanoparticles in the cells. It is known that the magnetotactic Deltaproteobacteria are ubiquitous and inhabit worldwide in the sediments of freshwater and marine environments. Mostly known MTB belonging to the Deltaproteobacteria are dissimilatory sulfate-reducing bacteria that biomineralize bullet-shaped magnetite nanoparticles, but only a few axenic cultures have been obtained so far. Here, we report the isolation, cultivation and characterization of a dissimilatory sulfate-reducing magnetotactic bacterium, which we designate “strain FSS-1”. We found that the strain FSS-1 is a strict anaerobe and uses casamino acids as electron donors and sulfate as an electron acceptor to reduce sulfate to hydrogen sulfide. The strain FSS-1 produced bullet-shaped magnetite nanoparticles in the cells and responded to external magnetic fields. On the basis of 16S rRNA gene sequence analysis, the strain FSS-1 is a member of the genus Desulfovibrio, showing a 96.7% sequence similarity to Desulfovibrio putealis strain B7-43T. Futhermore, the magnetosome gene cluster of strain FSS-1 was different from that of Desulfovibrio magneticus strain RS-1. Thus, the strain FSS-1 is considered to be a novel sulfate-reducing magnetotactic bacterium belonging to the genus Desulfovibrio.
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Kerans, Fransiscus, Lisa Lungaro, Asim Azfer, and Donald Salter. "The Potential of Intrinsically Magnetic Mesenchymal Stem Cells for Tissue Engineering." International Journal of Molecular Sciences 19, no. 10 (October 14, 2018): 3159. http://dx.doi.org/10.3390/ijms19103159.
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The magnetization of mesenchymal stem cells (MSC) has the potential to aid tissue engineering approaches by allowing tracking, targeting, and local retention of cells at the site of tissue damage. Commonly used methods for magnetizing cells include optimizing uptake and retention of superparamagnetic iron oxide nanoparticles (SPIONs). These appear to have minimal detrimental effects on the use of MSC function as assessed by in vitro assays. The cellular content of magnetic nanoparticles (MNPs) will, however, decrease with cell proliferation and the longer-term effects on MSC function are not entirely clear. An alternative approach to magnetizing MSCs involves genetic modification by transfection with one or more genes derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesizes single-magnetic domain crystals which are incorporated into magnetosomes. MSCs with either or mms6 and mmsF genes are followed by bio-assimilated synthesis of intracytoplasmic magnetic nanoparticles which can be imaged by magnetic resonance (MR) and which have no deleterious effects on MSC proliferation, migration, or differentiation. The stable transfection of magnetosome-associated genes in MSCs promotes assimilation of magnetic nanoparticle synthesis into mammalian cells with the potential to allow MR-based cell tracking and, through external or internal magnetic targeting approaches, enhanced site-specific retention of cells for tissue engineering.