Magnetotactic bacteria

About: Magnetotactic bacteria is a research topic. Over the lifetime, 1118 publications have been published within this topic receiving 43741 citations.

Magnetosomes on surface: an imaging study approach

Abstract: 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.

Identification of the Magnetic Poles on Strong Magnetic Grains from Meteorites Using Magnetotactic Bacteria

Abstract: Magnetotactic bacteria (north seeking bacteria) have been used to identify the magnetic S pole of iron-nickel grains selected from St. Severin LL6 chondrite. The results indicate that the bacteria are sensitive magnetic sensors which can be used to detect not only the S pole in the grains but also the directions of lines of magnetic force radiated from the grains. The magnetic coercive force and the stability of natural remanent magnetization can also be measured with the bacteria by applying a steady magnetic field. These methods can in principle be applied to terrestrial rocks having relatively strong natural remanent magnetization. Thus, the magnetotactic bacteria can give useful information for rock magnetism and paleomagnetism as a bio-magnetometer.Combining the method of south seeking bacteria and Bitter pattern analyses using colloidal magnetite particles, complex magnetization structures on the surface of Fe-Ni grains from the St. Severin meteorite have been revealed, which is important for an understanding the chondrite magnetism.

A Compass To Boost Navigation: Cell Biology of Bacterial Magnetotaxis

Abstract: Magnetotactic bacteria are aquatic or sediment-dwelling microorganisms able to take advantage of the Earth's magnetic field for directed motility. The source of this amazing trait is magnetosomes, unique organelles used to synthesize single nanometer-sized crystals of magnetic iron minerals that are queued up to build an intracellular compass. Most of these microorganisms cannot be cultivated under controlled conditions, much less genetically engineered, with only few exceptions. However, two of the genetically amenable Magnetospirillum species have emerged as tractable model organisms to study magnetosome formation and magnetotaxis. Recently, much has been revealed about the process of magnetosome biogenesis and dedicated structures for magnetosome dynamics and positioning, which suggest an unexpected cellular intricacy of these organisms. In this minireview, we summarize new insights and place the molecular mechanisms of magnetosome formation in the context of the complex cell biology of Magnetospirillum spp. First, we provide an overview on magnetosome vesicle synthesis and magnetite biomineralization, followed by a discussion of the perceptions of dynamic organelle positioning and its biological implications, which highlight that magnetotactic bacteria have evolved sophisticated mechanisms to construct, incorporate, and inherit a unique navigational device. Finally, we discuss the impact of magnetotaxis on motility and its interconnection with chemotaxis, showing that magnetotactic bacteria are outstandingly adapted to lifestyle and habitat.

Tethered Magnets Are the Key to Magnetotaxis: Direct Observations of Magnetospirillum magneticum AMB-1 Show that MamK Distributes Magnetosome Organelles Equally to Daughter Cells

Abstract: Magnetotactic bacteria are a unique group of bacteria that synthesize a magnetic organelle termed the magnetosome, which they use to assist with their magnetic navigation in a specific type of bacterial motility called magneto-aerotaxis. Cytoskeletal filaments consisting of the actin-like protein MamK are associated with the magnetosome chain. Previously, the function of MamK was thought to be in positioning magnetosome organelles; this was proposed based on observations via electron microscopy still images. Here, we conducted live-cell time-lapse fluorescence imaging analyses employing highly inclined and laminated optical sheet microscopy, and these methods enabled us to visualize detailed dynamic movement of magnetosomes in growing cells during the entire cell cycle with high-temporal resolution and a high signal/noise ratio. We found that the MamK cytoskeleton anchors magnetosomes through a mechanism that requires MamK-ATPase activity throughout the cell cycle to prevent simple diffusion of magnetosomes within the cell. We concluded that the static chain-like arrangement of the magnetosomes is required to precisely and consistently segregate the magnetosomes to daughter cells. Thus, the daughter cells inherit a functional magnetic sensor that mediates magneto-reception. IMPORTANCE Half a century ago, bacterial cells were considered a simple “bag of enzymes”; only recently have they been shown to comprise ordered complexes of macromolecular structures, such as bacterial organelles and cytoskeletons, similar to their eukaryotic counterparts. In eukaryotic cells, the positioning of organelles is regulated by cytoskeletal elements. However, the role of cytoskeletal elements in the positioning of bacterial organelles, such as magnetosomes, remains unclear. Magnetosomes are associated with cytoskeletal filaments that consist of the actin-like protein MamK. In this study, we focused on how the MamK cytoskeleton regulates the dynamic movement of magnetosome organelles in living magnetotactic bacterial cells. Here, we used fluorescence imaging to visualize the dynamics of magnetosomes throughout the cell cycle in living magnetotactic bacterial cells to understand how they use the actin-like cytoskeleton to maintain and to make functional their nano-sized magnetic organelles.

In Situ Generation of Gold Nanoparticles on Bacteria‐Derived Magnetosomes for Imaging‐Guided Starving/Chemodynamic/Photothermal Synergistic Therapy against Cancer

Abstract: There are several attractive opportunities for using magnetic nanomaterials for anticancer applications. Herein, a magnetic nanomaterial platform is successfully developed based on natural Fe3O4 magnetosomes extracted from the bacterium Magnetospirillum magneticum AMB‐1 for anticancer therapy. The authors initially functionalize the magnetosome membranes in situ with gold nanoparticles to construct an attractive core‐satellite structure. Subsequently, the physical properties and application potentials of these structures are characterized as contrast agents for photoacoustic imaging and magnetic resonance imaging and as therapeutic agents with selective magnetic field guidance for diverse antitumor modalities, including starving, chemodynamic, and photothermal therapies. Owing to the high‐performance imaging‐guided synergistic effect, only a single injection and single laser irradiation result in excellent therapeutic efficacy against tumor growth in multiple cell‐derived xenograft tumor models and, most notably, patient‐derived organoid and patient‐derived xenograft tumor models. The demonstrations of the use of natural magnetic nanomaterials to achieve strong and synergistic antitumor performances highlight the promising application potential of this flexible and easy‐to‐prepare platform for developing innovative treatments for diseases in humans.