Bibliographies thématiques / "magnetosomi"

Littérature scientifique sur le sujet « "magnetosomi" »

Auteur : Grafiati
Publié le 11 mars 2023

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Articles de revues sur le sujet ""magnetosomi""

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Taoka, Azuma, Ryuji Asada, Hideaki Sasaki, Kazushi Anzawa, Long-Fei Wu et Yoshihiro Fukumori. « Spatial Localizations of Mam22 and Mam12 in the Magnetosomes of Magnetospirillum magnetotacticum ». Journal of Bacteriology 188, no 11 (1 juin 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 et Dirk Schüler. « Identification of Promoters for Efficient Gene Expression in Magnetospirillum gryphiswaldense ». Applied and Environmental Microbiology 75, no 12 (24 avril 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, et Dirk Schüler. « Expression of Green Fluorescent Protein Fused to Magnetosome Proteins in Microaerophilic Magnetotactic Bacteria ». Applied and Environmental Microbiology 74, no 15 (6 juin 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 et Dirk Schüler. « Overproduction of Magnetosomes by Genomic Amplification of Biosynthesis-Related Gene Clusters in a Magnetotactic Bacterium ». Applied and Environmental Microbiology 82, no 10 (11 mars 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 et Damien Faivre. « Structural purity of magnetite nanoparticles in magnetotactic bacteria ». Journal of The Royal Society Interface 8, no 60 (19 janvier 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 et Peter R. Buseck. « Crystal habits and magnetic microstructures of magnetosomes in coccoid magnetotactic bacteria ». Anais da Academia Brasileira de Ciências 78, no 3 (septembre 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 et 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 (7 décembre 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 et 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 (1 août 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 et 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 (19 décembre 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 et Milan Timko. « The Effect of Sonication on Acoustic Properties of Biogenic Ferroparticle Suspension ». Archives of Acoustics 41, no 1 (1 mars 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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Thèses sur le sujet ""magnetosomi""

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Trubitsyn, Denis. « Magnetosome formation in marine vibrio MV-1 ». Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7589.

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Marine vibrio MV-1 is a magnetotactic bacterium capable of aligning its cell in response to the Earth’s magnetic field. This ability is due to the presence of chainlike structures comprising magnetosomes, magnetite particles enclosed in a lipid membrane with associated proteins. Strain MV-1 differs from other, bettercharacterized strains of magnetotactic bacteria as the cells produce higher amounts of biomagnetite per litre of culture and its magnetosomes are unique in shape. This study investigates the presence and organisation of a gene cluster termed a “magnetosome island” within the genome of MV-1. In other magnetotactic bacteria this genomic region has been shown to contain many of the genes associated with magnetosome formation but has not been previously investigated for MV-1. One of the conserved fragments of this region was amplified using degenerate primers followed by extension of the known sequence using inverse PCR based technique and constructing plasmid libraries. Sequencing of the genome of strain MV-1 was accomplished as a part of this study. Significant work was done on comparison of the sequence quality obtained from SOLEXA, 454 and Sanger sequencing technologies. A number of obtained contigs were joined manually and the resulting sequence was automatically annotated using RAST. The obtained genome sequence of 3.6 Mb with a G+C content of 54.3 % was preliminarily analysed and used to search for magnetosome related genes. This study also analysed proteins associated with the magnetosomes of strain MV-1 using MALDI-TOF, LC-MS and Orbitrap mass spectrometry. These approaches allowed the identification of a number of proteins in the isolated magnetosome membrane fraction. Some of these proteins have very low similarity with other characterized proteins (either in magnetotactic bacteria or in other organisms). Another significant point is that genes that code for proteins such as MamR, MamK and MmsF were found to be present in several homologous copies within the “magnetosome island” of MV-1. Interestingly, this study shows that all homologous copies of these proteins were identified in the magnetosome membrane fraction. Generation of knock-out mutants of several specific genes from the “magnetosome island” of strain MV-1 was attempted; constructs were made based on suicide plasmids carrying the cre-lox or I-SceI systems. Despite altering numerous experimental conditions it was not possible to obtain conclusive evidence of the isolation of MV-1 transconjugants containing the integrated constructs. In order to investigate the cell localization of the magnetosome associated protein CAV30779.1, an enhanced green fluorescent protein (EGFP) fusion based construct was generated and transferred into MV-1 cells. The EGFP fluorescent protein fusions within the cells were detected by microscopy. This study reveals novel information about magnetosome formation in marine vibrio MV-1. The obtained results provide an important foundation for further investigation of this organism and contribute towards broadening the knowledge of the complex process of magnetosome formation in bacteria.
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Liu, Shuk Yi. « Encapsulation of magnetosomes in lipid vesicles ». HKBU Institutional Repository, 2004. http://repository.hkbu.edu.hk/etd_ra/615.

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Lohsse, Anna. « Genome engineering of the magnetosome island in Magnetospirillum gryphiswaldense ». Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-181516.

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Bain, Jennifer. « Biomimetic synthesis of magnetosomes for biomedical application ». Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/12312/.

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Li, Yingjie. « Oxygen regulation and redox control of magnetosome biomineralization in Magnetospirillum gryphiswaldense ». Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-174813.

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Kiani, Alibagheri Bahareh [Verfasser], et Stefan [Akademischer Betreuer] Klumpp. « On structural properties of magnetosome chains / Bahareh Kiani Alibagheri ; Betreuer : Stefan Klumpp ». Potsdam : Universität Potsdam, 2017. http://d-nb.info/1218402628/34.

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Mumper, Eric Keith. « Mixotrophic Magnetosome-Dependent Magnetoautotrophic Metabolism of Model Magnetototactic Bacterium Magnetospirillum magneticum AMB-1 ». The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1551880645784717.

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Lohße, Anna [Verfasser], et Dirk [Akademischer Betreuer] Schüler. « Genome engineering of the magnetosome island in Magnetospirillum gryphiswaldense / Anna Lohße. Betreuer : Dirk Schüler ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1069743704/34.

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Juodeikis, Rokas. « Engineering membranes in Escherichia coli : the magnetosome, LemA protein family and outer membrane vesicles ». Thesis, University of Kent, 2016. https://kar.kent.ac.uk/61062/.

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Magnetosomes are membranous organelles found in magnetotactic bacteria (MTB). The organelle consist of ferromagnetic crystals housed within a lipid bilayer chained together by an actin-like filament and allows MTB to orient within magnetic fields. The genetic information required to produce these organelles has been linked to four different operons, encoding for 30 genes. These membranous organelles and the magnetic minerals housed within have various biotechnological applications, therefore enhanced recombinant production of such structures in a model organism holds significant potential. The research described in this thesis is focuses on the production of recombinant magnetosomes in the model organism Escherichia coli. Cloning the genes involved in the generation of the organelle individually or in various combinations resulted in the construction of over 100 different plasmids, compatible with the model organism. SDS-PAGE and electron microscopy analysis was used to characterise E. coli cells harbouring these constructs. The observation of electron dense particles, arranged in a chain structure, show that magnetosome generation in the model organism is possible, but is highly dependent on the growth conditions used. The need for specific growth conditions is later backed up by the analysis of the maturation of the cytochrome c proteins involved in magnetosome biomineralisation, which can only be correctly processed under certain conditions. Individual production of two different magnetosome proteins, MamQ or MamY, allowed the generation of various membranous structures in E. coli observed in 48.9% and 56.2% of the whole population of cells respectively. Combinations of these with MamI, MamL or MamB in a variety of combinations led to a variation in the phenotype observed. Bioinformatics analysis of MamQ led to the discovery of a novel membrane restructuring protein family, the LemA protein family, present in a broad range of bacteria. Four different LemA proteins from Bacillus megaterium, Clostridium kluyveri, Brucella melitensis or Pseudomonas aeruginosa were then produced in E. coli and the analysis of the resulting strains revealed the presence of novel intracellular membranous structures which vary in size, form and localisation. Furthermore, when attempts were made to target these proteins for the modification of the outer membrane, a mechanism for increased outer membrane vesicle generation was serendipitously discovered and different effects of these proteins were once again observed. Together, the results described shows good evidence for recombinant magnetosome production in E. coli and opens a new avenue of membrane engineering in this commonly used organism. Such membranous structures have various biotechnological applications, such as enhanced metabolic engineering potential or specialised lipid vesicle production.
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Mannoubi, Soumaya. « Caractérisation de MamK et Mamk-like les "actins-like" responsables de l'alignement des magnétosomes chez Magnetsirillum magneticum AMB-1 ». Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4004.

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Les bactéries magnétotactiques (MTB) ont la capacité de s'orienter dans un champ magnétique grâce à un organite procaryote constitué d'un nanocristal magnétique biominéralisé et entouré d'une membrane biologique : le magnétosome. La synthèse de cet organite est un processus complexe contrôlé génétiquement par une série de gènes spécifiques aux MTB (les gènes mam) qui sont regroupés sur le chromosome bactérien. Chez la souche modèle Magnetospirillum magneticum AMB-1 cet ensemble de gènes forme un îlot génomique (MAI) auquel s'ajoute un second groupe distinct de 7 gènes homologues aux gènes mam (gènes mam-like) récemment identifié dont le rôle physiologique est très peu caractérisé. Parmi les produits des gènes mam, MamK est impliqué dans l'alignement des magnétosomes. Cette « actin-like » prokaryote qui forme des filaments selon un processus ATP-dépendant a été caractérisée ces dernières années. Dans le MIS de AMB-1, un gène homologue mamK-like a été identifié. Ainsi différentes approches pluridisciplinaires ont été mises en place pour comprendre le rôle de MamK et MamK-like. L'expression des gènes du MIS a été quantifiée. Les souches dépourvues des gènes mamK et mamK-like ainsi que le double mutant ont été obtenues puis phénotypées par différentes techniques d'imagerie. Les interactions entre les deux protéines ont été également testées. Enfin, les deux protéines ont été et leurs propriétés biochimiques caractérisées. L'ensemble de ces données nous permet de proposer un modèle selon lequel MamK et MamK-like participeraient tous deux à l'alignement des magnétosomes bactériens, vraisemblablement par la formation de filaments hybrides
Magnetotactic bacteria (MTB) have the ability to orient in a magnetic field through a prokaryotic organelle composed of a magnetic nanocrystal surrounded by a biological membrane: the magnetosome. The synthesis of this organelle is a genetically complex process controlled by a series of specific genes (mam genes) grouped together on the bacterial chromosome. In the strain model Magnetospirillum magneticum AMB-1 this set of genes form a genomic island (MAI) and a second distinct group of seven genes homologous to mam genes (mam-like genes) recently identified. The physiological role of this islet magnetosome (MIS) is very little characterized to date.Among the products of mam genes, MamK is involved in the alignment of the magnetosomes. This « actin-like » which forms prokaryote filaments according an ATP - dependent process has been characterized in recent years. In the MIS of AMB-1, a homologous gene mamK-like was identified. And various multidisciplinary approaches have been developed to understand the role of MamK and MamK-like. The MIS gene expression was quantified. The strains lacking genes of mamK, mamK-like and the obtained of double mutant were then phenotyped by different imaging techniques. The interactions between the two proteins were also tested. Finally, the two proteins were overexpressed and their biochemical properties characterized. All of these data allows us to propose a model whereby MamK and MamK-like participate in both the alignment of bacterial magnetosomes, presumably by the formation of hybrid filaments
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Livres sur le sujet ""magnetosomi""

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Schüler, Dirk, dir. Magnetoreception and Magnetosomes in Bacteria. Berlin, Heidelberg : Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/11741862.

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Schüler, Dirk. Magnetoreception and Magnetosomes in Bacteria. Springer, 2010.

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Schüler, Dirk. Magnetoreception and Magnetosomes in Bacteria. Springer London, Limited, 2006.

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Magnetoreception and Magnetosomes in Bacteria (Microbiology Monographs). Springer, 2006.

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Chapitres de livres sur le sujet ""magnetosomi""

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Davila, Alfonso F. « Magnetosome ». Dans Encyclopedia of Astrobiology, 1–2. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_924-3.

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Davila, Alfonso F. « Magnetosome ». Dans Encyclopedia of Astrobiology, 1428–29. Berlin, Heidelberg : Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_924.

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Davila, Alfonso F. « Magnetosome ». Dans Encyclopedia of Astrobiology, 949–50. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_924.

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Masó-Martínez, Marta, Paul D. Topham et Alfred Fernández-Castané. « Magnetosomes ». Dans Fundamentals of Low Dimensional Magnets, 309–24. Boca Raton : CRC Press, 2022. http://dx.doi.org/10.1201/9781003197492-16.

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Cypriano, Jefferson, Júlia Castro, Igor Taveira, Tarcisio Correa, Daniel Acosta-Avalos, Fernanda Abreu, Marcos Farina et Carolina N. Keim. « Magnetosome Biomineralization by Magnetotactic Bacteria ». Dans Microbiology Monographs, 243–81. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-80807-5_7.

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Scheffel, André, et Dirk Schüler. « Magnetosomes in Magnetotactic Bacteria ». Dans Microbiology Monographs, 167–91. Berlin, Heidelberg : Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/7171_024.

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Frankel, Richard B., et Dennis A. Bazylinski. « Magnetosomes and Magneto-Aerotaxis ». Dans Contributions to Microbiology, 182–93. Basel : KARGER, 2009. http://dx.doi.org/10.1159/000219380.

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Bazylinski, Dennis A., Christopher T. Lefèvre et Brian H. Lower. « Magnetotactic Bacteria, Magnetosomes, and Nanotechnology ». Dans Nanomicrobiology, 39–74. New York, NY : Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-1667-2_3.

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Arakaki, Atsushi, Michiko Nemoto et Tadashi Matsunaga. « Molecular Bioengineering of Magnetosomes for Biotechnological Applications ». Dans Coordination Chemistry in Protein Cages, 241–71. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118571811.ch10.

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Lefèvre, Christopher T., Fernanda Abreu, Ulysses Lins et Dennis A. Bazylinski. « A Bacterial Backbone : Magnetosomes in Magnetotactic Bacteria ». Dans Metal Nanoparticles in Microbiology, 75–102. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-18312-6_4.

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Actes de conférences sur le sujet ""magnetosomi""

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Han, Lei, Shuangyan Li, Yong Yang, Fengmei Zhao, Jie Huang et Jin Chang. « Research on the Structure and Performance of Bacterial Magnetic Nanoparticles ». Dans 2007 First International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2007. http://dx.doi.org/10.1115/mnc2007-21137.

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Magnetite nanocrystal has been widely used in many fields. Recently, a new magnetite nanocrystal, called magnetosome, has been found in magnetotactic bacteria. In this article, we researched on the properties of magnetosomes detailedly, such as crystalline, morphology, crystal-size distributions, vitro cytotoxicity, and magnetic properties and quantified primary amino groups on the magnetosomes membrane surface by fluorescamine assay for the first time. From the results, it was clear that magnetosomes have more potential in the biomedical applications than synthetic magnetite.
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Wilson, Mary E., Lina M. González, Warren C. Ruder et Philip R. LeDuc. « Engineering Magnetic Nanomaterial Production in Magnetotactic Bacteria Through Gene Regulation ». Dans ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80446.

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Magnetotactic bacteria endogenously synthesize intracellular magnetic nanoparticles (magnetosomes); however, little is known regarding the genetic regulatory networks that control magnetosome production. In this paper, we explore the genetic response of Magnetospirillum magneticum strain AMB-1 to an applied electromagnetic field as a means to identify genes activated by magnetic stimulation. The expression of magnetosome island, flagellar and cytoskeletal genes was found to be differentially altered by magnetic stimulation at short and long times points. These results indicate previously uncharacterized endogenous gene network modules that could be exploited to engineer magnetic bacteria as magnetic nanomaterial producing-machines through gene regulation.
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Vainshtein, Mikhail, Ekaterina Kudryashova, Natalia Suzina, Elena Ariskina et Vladimir Sorokin. « Functions of non-crystal magnetosomes in bacteria ». Dans SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, sous la direction de Richard B. Hoover. SPIE, 1998. http://dx.doi.org/10.1117/12.319854.

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Zhang, Yuhong, Shiying Ren, Hongqing Wu et Tian Xiao. « Magnetosome Assembling and Optimization of Growth Conditions of the Magnetospirillum Magneticum AMB-1 Strain ». Dans 2008 2nd International Conference on Bioinformatics and Biomedical Engineering. IEEE, 2008. http://dx.doi.org/10.1109/icbbe.2008.686.

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Martel, Sylvain, Mahmood Mohammadi et Nisryn Mokrani. « Switching Between Magnetic or Oxigen Sensory Input for the MC-1 Flagellated Bacteria to be Used for Controlling the Motion of Swarms of Bacterial Microscale Nanorobots ». Dans ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13302.

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Our previous studies have shown that the flagellated nanomotors combined with the nanometer-sized chain of magnetosomes of a single Magnetotactic Bacterium (MTB) can be used as an effective integrated propulsion and steering system for microscale nanorobots. In this case, magnetotaxis has been exploited to control the swimming direction of the flagellated bacteria. This was done by inducing a directional torque on the chain of magnetosomes embedded in each bacterial cell. This approach allowed us to control swarms of flagellated bacteria of type MC-1 to accomplish relatively complex computer coordinated tasks such as micro-assemblies and drug deliveries, to name but only two examples. But the motion of each cell can also be influenced by other sensory means besides magnetotaxis, and includes chemotaxis, phototaxis, and aerotaxis. Here we show examples of MC-1 flagellated bacteria being controlled by magnetotaxis or aerotaxis. It is then demonstrated that these flagellated bacteria can not only provide an effective propulsion and steering system for future bio-nanorobots but also various sensory means capable of influencing their motions and swarm formations.
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Martel, Sylvain, et Mahmood Mohammadi. « Towards Mass-Scale Micro-Assembly Systems Using Magnetotactic Bacteria ». Dans ASME 2011 International Manufacturing Science and Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/msec2011-50171.

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Magnetotactic bacteria (MTB) can be used in a coordinated fashion to assemble micro-objects in an orderly manner. To perform micro-assembly tasks, magnetotaxis-based control is used where a directional magnetic field is generated to induce a torque on an embedded chain of membrane-based magnetic nanoparticles (MNP) named magnetosomes. Such chain acts like a nano-compass or a nano-steering system embedded in each bacterium. Such magnetotaxis-based control is then used to orient the MTB in such a way that the laminar flow created by their flagella bundles provides a displacement force on the micro-objects being assembled. Since the force is generated by the bacteria, relatively large micro-objects can be moved with no requirement for electrical energy except for a relatively small value required for inducing a directional torque on the chain of magnetosomes in the cells. Because the energy required to generate the directional torque is independent on the population of MTB being involved but the displacement force can be scaled up with the use of a larger swarm while the total workspace would typically be at microscale dimensions, the energy required for the coils configuration around such workspace and responsible for generating the directional torque can be reduced further to a very low level and hence, makes the implementation of mass-scale bacterial micro-assembly systems, a viable approach. Based on these findings, we propose a corresponding mass-scale system based on many workspaces, each relying on a swarm of MTB to perform micro-assembly tasks in parallel.
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Felfoul, O., N. Mokrani, M. Mohammadi et S. Martel. « Effect of the chain of magnetosomes embedded in magnetotactic bacteria and their motility on Magnetic Resonance imaging ». Dans 2010 32nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2010). IEEE, 2010. http://dx.doi.org/10.1109/iembs.2010.5627106.

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