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Microorganisms Apr 2022Multicellular magnetotactic prokaryotes (MMPs) are a unique group of magnetotactic bacteria that are composed of 10-100 individual cells and show coordinated swimming...
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 (FeO) and/or greigite (FeS) 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 . 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.
PubMed: 35630369
DOI: 10.3390/microorganisms10050925 -
Proceedings of the National Academy of... Jun 2024Magnetotactic bacteria produce chains of nanoscopic iron minerals used for navigation, which can be preserved over geological timescales in the form of magnetofossils....
Magnetotactic bacteria produce chains of nanoscopic iron minerals used for navigation, which can be preserved over geological timescales in the form of magnetofossils. Micrometer-sized magnetite crystals with unusual shapes suggesting a biologically controlled mineralization have been found in the geological record and termed giant magnetofossils. The biological origin and function of giant magnetofossils remains unclear, due to the lack of modern analogues to giant magnetofossils. Using distinctive Ptychographic nanotomography data of Precambrian (1.88 Ga) rocks, we recovered the morphology of micrometric cuboid grains of iron oxides embedded in an organic filamentous fossil to construct synthetic magnetosomes. Their morphology is different from that of previously found giant magnetofossils, but their occurrence in filamentous microfossils and micromagnetic simulations support the hypothesis that they could have functioned as a navigation aid, akin to modern magnetosomes.
Topics: Fossils; Magnetosomes; Ferrosoferric Oxide; Geologic Sediments
PubMed: 38805285
DOI: 10.1073/pnas.2319148121 -
Molecules (Basel, Switzerland) Aug 2022A number of materials are studied in the field of magnetic hyperthermia. In general, the most promising ones appear to be iron oxide particle nanosystems. This is also...
A number of materials are studied in the field of magnetic hyperthermia. In general, the most promising ones appear to be iron oxide particle nanosystems. This is also indicated in some clinical trial studies where iron-based oxides were used. On the other hand, the type of material itself provides a number of variations on how to tune hyperthermia indicators. In this paper, magnetite nanoparticles in various forms were analyzed. The nanoparticles differed in the core size as well as in the form of their arrangement. The arrangement was determined by the nature of the surfactant. The individual particles were covered chemically by dextran; in the case of chain-like particles, they were encapsulated naturally in a lipid bilayer. It was shown that in the case of chain-like nanoparticles, except for relaxation, a contribution from magnetic hysteresis to the heating process also appears. The influence of the chosen methodology of magnetic field generation was also analyzed. In addition, the influence of the chosen methodology of magnetic field generation was analyzed. The application of a rotating magnetic field was shown to be more efficient in generating heat than the application of an alternating magnetic field. However, the degree of efficiency depended on the arrangement of the magnetite nanoparticles. The difference in the efficiency of the rotating magnetic field versus the alternating magnetic field was much more pronounced for individual nanoparticles (in the form of a magnetic fluid) than for systems containing chain nanoparticles (magnetosomes and a mix of magnetic fluid with magnetosomes in a ratio 1:1).
Topics: Cell Line, Tumor; Hyperthermia, Induced; Magnetic Fields; Magnetite Nanoparticles; Magnetosomes
PubMed: 36080372
DOI: 10.3390/molecules27175605 -
Frontiers in Immunology 2021Neural stem cell (NSC) therapy is a promising therapeutic strategy for stroke. Researchers have frequently carried out genetic modification or gene editing of stem...
Neural stem cell (NSC) therapy is a promising therapeutic strategy for stroke. Researchers have frequently carried out genetic modification or gene editing of stem cells to improve survival or therapeutic function. However, NSC transplantation carries the risk of immune rejection, and genetic modification or gene-editing might further increase this risk. For instance, recent studies have reported on manipulating the stem cell genome and transplantation the insertion of an exogenous gene derived from magnetotactic bacteria. However, whether transgene-modified stem cells are capable of inducing immunological reactions has not been explored. Although NSCs rarely express the major histocompatibility complex (MHC), they can still cause some immunological issues. To investigate whether transgene-modified NSCs aggravate immunological responses, we detected the changes in peripheral immune organs and intracerebral astrocytes, glial cells, and MHC-I and MHC-II molecules after the injection of GFP-labeled or -GFP-labeled NSCs in a rat model. Xenogeneic human embryonic kidney (HEK-293T) cells were grafted as a positive control group. Our results indicated that xenogeneic cell transplantation resulted in a strong peripheral splenic response, increased astrocytes, enhanced microglial responses, and upregulation of MHC-I and MHC-II expression on the third day of transplantation. But they decreased obviously except Iba-1 positive cells and MHC-II expression. When injection of both -GFP-labeled NSCs and GFP-labeled NSCs also induced similar responses as HEK-293T cells on the third days, but MHC-I and MHC-II expression decreased 3 weeks after transplantation. In addition, transgene-modified NSCs did not produce peripheral splenic response responses as well as astrocytes, microglial cells, MHC-I and MHC-II positive cells responses when compared with non-modified NSCs. The present study provides preliminary evidence that transgenic modification does not aggravate immunological responses in NSC transplantation.
Topics: Animals; Astrocytes; Brain; Cell Proliferation; Cells, Cultured; DNA, Bacterial; Genes, Bacterial; Green Fluorescent Proteins; HEK293 Cells; Humans; Kidney; Magnetite Nanoparticles; Magnetosomes; Magnetospirillum; Microglia; Neural Stem Cells; Rats; Recombinant Proteins; Spleen; Stem Cell Transplantation; Transgenes; Transplantation, Heterologous
PubMed: 34248998
DOI: 10.3389/fimmu.2021.697203 -
Biotechnology Reports (Amsterdam,... Mar 2020Lipase was immobilized onto bacterial magnetosomes using glutaraldehyde cross-linking and confirmed by Fourier transform infrared spectrometry (FT-IR) and Scanning...
Lipase was immobilized onto bacterial magnetosomes using glutaraldehyde cross-linking and confirmed by Fourier transform infrared spectrometry (FT-IR) and Scanning electron microscopy (SEM). Enzyme activity of immobilised lipase as well as free lipase was estimated by the release of p-nitro phenol due to the hydrolysis of -nitro phenyl acetate (pNPA). The immobilisation yield of lipase onto magnetosome was found to be 88 %. The optimal pH (7) and temperature (40 °C) for activity was standardised and found to be similar to free lipase. The stored immobilized lipase maintained higher activity even after 30 days at a temperature of 4 °C whereas compared to free lipase. Immobilized lipase found to have removed vegetable oil stain and showed higher cleaning efficiency when compared to free lipase. The results suggest that bacterial magnetosome displays great potential as a support material for the immobilization of industrial enzymes such as lipase.
PubMed: 31993344
DOI: 10.1016/j.btre.2020.e00422 -
Applied and Environmental Microbiology Dec 2020employs iron-rich nanoparticles for magnetic navigation within environmental redox gradients. This behavior termed magneto-aerotaxis was previously shown to rely on the...
employs iron-rich nanoparticles for magnetic navigation within environmental redox gradients. This behavior termed magneto-aerotaxis was previously shown to rely on the sensory pathway CheOp1, but the precise localization of CheOp1-related chemoreceptor arrays during the cell cycle and its possible interconnection with three other chemotaxis pathways have remained unstudied. Here, we analyzed the localization of chemoreceptor-associated adaptor protein CheW and histidine kinase CheA by superresolution microscopy in a spatiotemporal manner. CheW localized in dynamic clusters that undergo occasional segregation and fusion events at lateral sites of both cell poles. Newly formed smaller clusters originating at midcell before completion of cytokinesis were found to grow in size during the cell cycle. Bipolar CheA localization and formation of aerotactic swim halos were affected depending on the fluorescent protein tag, indicating that CheA localization is important for aerotaxis. Furthermore, polar CheW localization was independent of to but lost in the absence of or Results were corroborated by the detection of a direct protein interaction between CheA and CheW and by the observation that - and -encoded CheW paralogs localized in spatially distinct smaller clusters at the cell boundary. Although the findings of a minor aerotaxis-related CheOp4 phenotype and weak protein interactions between CheOp1 and CheOp4 by two-hybrid analysis implied that CheW and CheW might be part of the same chemoreceptor array, CheW was localized in spatially distinct polar-lateral arrays independent of CheOp1, suggesting that CheOp1 and CheOp4 are also not connected at the molecular level. Magnetotactic bacteria (MTB) use the geomagnetic field for navigation in aquatic redox gradients. However, the highly complex signal transduction networks in these environmental microbes are poorly understood. Here, we analyzed the localization of selected chemotaxis proteins to spatially and temporally resolve chemotaxis array localization in Our findings suggest that bipolar localization of chemotaxis arrays related to the key signaling pathway CheOp1 is important for aerotaxis and that CheOp1 signaling units assemble independent of the three other chemotaxis pathways present in Overall, our results provide deeper insights into the complex organization of signaling pathways in MTB and add to the general understanding of environmental bacteria possessing multiple chemotaxis pathways.
Topics: Bacterial Proteins; Chemotaxis; Histidine Kinase; Magnetospirillum; Signal Transduction
PubMed: 33067189
DOI: 10.1128/AEM.02229-20 -
BMC Microbiology Feb 2021Magnetosome formation in the alphaproteobacterium Magnetospirillum gryphiswaldense is controlled by more than 30 known mam and mms genes clustered within a large genomic...
BACKGROUND
Magnetosome formation in the alphaproteobacterium Magnetospirillum gryphiswaldense is controlled by more than 30 known mam and mms genes clustered within a large genomic region, the 'magnetosome island' (MAI), which also harbors numerous mobile genetic elements, repeats, and genetic junk. Because of the inherent genetic instability of the MAI caused by neighboring gene content, the elimination of these regions and their substitution by a compact, minimal magnetosome expression cassette would be important for future analysis and engineering. In addition, the role of the MAI boundaries and adjacent regions are still unclear, and recent studies indicated that further auxiliary determinants for magnetosome biosynthesis are encoded outside the MAI. However, techniques for large-scale genome editing of magnetic bacteria are still limited, and the full complement of genes controlling magnetosome formation has remained uncertain.
RESULTS
Here we demonstrate that an allelic replacement method based on homologous recombination can be applied for large-scale genome editing in M. gryphiswaldense. By analysis of 24 deletion mutants covering about 167 kb of non-redundant genome content, we identified genes and regions inside and outside the MAI irrelevant for magnetosome biosynthesis. A contiguous stretch of ~ 100 kb, including the scattered mam and mms6 operons, could be functionally substituted by a compact and contiguous ~ 38 kb cassette comprising all essential biosynthetic gene clusters, but devoid of interspersing irrelevant or problematic gene content.
CONCLUSIONS
Our results further delineate the genetic complement for magnetosome biosynthesis and will be useful for future large-scale genome editing and genetic engineering of magnetosome biosynthesis.
Topics: Genes, Bacterial; Genome, Bacterial; Genomics; Magnetosomes; Magnetospirillum; Multigene Family; Mutation; Operon
PubMed: 33632118
DOI: 10.1186/s12866-021-02124-2 -
Journal of Molecular Microbiology and... 2013
Topics: Bacteria; Bacterial Chromatophores; Intracellular Membranes; Magnetosomes; Nuclear Envelope; Organelles
PubMed: 23615191
DOI: 10.1159/000346496 -
Scanning 2012In this study, we deposited isolated magnetosomes from magnetotactic bacteria Magnetospirillum strain AMB-1 onto solid surfaces using spin coating (SC) and drop coating... (Comparative Study)
Comparative Study
In this study, we deposited isolated magnetosomes from magnetotactic bacteria Magnetospirillum strain AMB-1 onto solid surfaces using spin coating (SC) and drop coating (DC) techniques. Four imaging techniques have been used to visualize the sample structure: scanning and transmission electron microscopy (SEM, TEM), atomic and magnetic force microscopy (AFM, MFM). Additionally, dynamic light scattering was applied to measure the hydrodynamic radius of agglomerated/aggregated magnetosomes in a liquid environment. This manuscript discusses observed differences between structures obtained by two deposition techniques, i.e. possible interactions and factors responsible for magnetosomes' formation, their morphology on surfaces as a result of agglomeration and aggregation phenomena. Moreover, topography and homogeneity of obtained structures as well as thickness of protein-based membrane were also examined and described. Using high-resolution TEM, we analyzed the size of magnetic cores, their crystal structure and quality. We found that the SC technique provides a homogenous layer of magnetosomes and hydrophilization of silicon surfaces improves the deposition of magnetosomes. However, due to strong hydrogen interaction to the hydrophilic silicone surface, the organic membrane of magnetosomes is mostly flattened. As a matter of fact, the size distributions of magnetosomes deposited by SC and DC techniques (logarithmic-normal tendency) differ from the Feret diameter distribution (normal). Furthermore, our study confirms the good crystalline quality of magnetosomes' cores. It also shows that they are magnetic in the all their volume.
Topics: HEPES; Hydrodynamics; Hydrophobic and Hydrophilic Interactions; Image Processing, Computer-Assisted; Magnetics; Magnetite Nanoparticles; Magnetosomes; Magnetospirillum; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Particle Size; Silicones; Solutions; Surface Properties
PubMed: 21953296
DOI: 10.1002/sca.20292 -
Journal of Proteomics Feb 2018Magnetotactic bacteria produce chains of complex membrane-bound organelles that direct the biomineralization of magnetic nanoparticles and serve for magnetic field...
UNLABELLED
Magnetotactic bacteria produce chains of complex membrane-bound organelles that direct the biomineralization of magnetic nanoparticles and serve for magnetic field navigation. These magnetosome compartments have recently emerged as a model for studying the subcellular organization of prokaryotic organelles. Previous studies indicated the presence of specific proteins with various functions in magnetosome biosynthesis. However, the exact composition and stoichiometry of the magnetosome subproteome have remained unknown. In order to quantify and unambiguously identify all proteins specifically targeted to the magnetosome membrane of the Alphaproteobacterium Magnetospirillum gryphiswaldense, we analyzed the protein composition of several cellular fractions by semi-quantitative mass spectrometry. We found that nearly all genuine magnetosome membrane-integral proteins belong to a well-defined set of previously identified proteins encoded by gene clusters within a genomic island, indicating a highly controlled protein composition. Magnetosome proteins were present in different quantities with up to 120 copies per particle as estimated by correlating our results with available quantitative Western blot data. This high abundance suggests an unusually crowded protein composition of the membrane and a tight packing with transmembrane domains of integral proteins. Our findings will help to further define the structure of the organelle and contribute to the elucidation of magnetosome biogenesis.
BIOLOGICAL SIGNIFICANCE
Magnetosomes are one of the most complex bacterial organelles and consist of membrane-bounded crystals of magnetic minerals. The exact composition and stoichiometry of the associated membrane integral proteins are of major interest for a deeper understanding of prokaryotic organelle assembly; however, previous proteomic studies failed to reveal meaningful estimations due to the lack of precise and quantitative data, and the inherently high degree of accumulated protein contaminants in purified magnetosomes. Using a highly sensitive mass spectrometer, we acquired proteomic data from several cellular fractions of a magnetosome producing magnetotactic bacterium and developed a comparative algorithm to identify all genuine magnetosome membrane-integral proteins and to discriminate them from contaminants. Furthermore, by combining our data with previously published quantitative Western blot data, we were able to model the protein copy number and density within the magnetosome membrane. Our results suggest that the magnetosome membrane is specifically associated with a small subset of integral proteins that are tightly packed within the lipid layer. Our study provides by far the most comprehensive estimation of magnetosomal protein composition and stoichiometry and will help to elucidate the complex process of magnetosome biogenesis.
Topics: Magnetosomes; Magnetospirillum; Mass Spectrometry; Membrane Proteins; Multigene Family; Proteome
PubMed: 29054541
DOI: 10.1016/j.jprot.2017.10.007