Magnetotactic bacteria

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

Manganese incorporation into the magnetosome magnetite: magnetic signature of doping

Abstract: The biomineralization of magnetotactic bacterial magnetite nanoparticles is a topic of intense research due to the particles' narrow size distribution and magnetic properties. Incorporation of foreign metal ions into the crystal matrix of magnetotactic bacterial magnetite has been previously examined by a number of investigators. In this study, cells of a magnetotactic bacterium, Magnetospirillum gryphiswaldense strain MSR-1 were grown in the presence of manganese, ruthe- nium, zinc and vanadium, of which only manganese was incorporated within the magnetosome magnetite crystals. We demonstrate that the magnetic properties of magnetite crystals of magnetotactic bacteria can be significantly altered by the incorporation of metal ions, other than iron, in the crystal structure. The Verwey transition serves as a unique marker to probe the incorporation of the dopant within the magnetosome: manganese incorporation into the magnetite nanocrystals is signaled by a suppression oftheVerwey transition,aswell as by changes in the crystallinestructureand chemicalcomposition ofmagnetosome magnetite.

Two Genera of Magnetococci with Bean-like Morphology from Intertidal Sediments of the Yellow Sea, China

Abstract: Magnetotactic bacteria have the unique capacity of being able to swim along geomagnetic field lines. They are Gram-negative bacteria with diverse morphologies and variable phylogenetic relatedness. Here, we describe a group of uncultivated marine magnetococci collected from intertidal sediments of Huiquan Bay in the Yellow Sea. They were coccoid-ovoid in morphology, with an average size of 2.8 +/- 0.3 mu m by 2.0 +/- 0.2 mu m. Differential interference contrast microscopy, fluorescence microscopy, and transmission electron microscopy revealed that each cell was apparently composed of two hemispheres. The cells synthesized iron oxide-type magnetosomes that clustered on one side of the cell at the interface between the two hemispheres. In some cells two chains of magnetosomes were observed across the interface. Each cell had two bundles of flagella enveloped in a sheath and displayed north-seeking helical motion. Two 16S rRNA gene sequences having 91.8% identity were obtained, and their authenticity was confirmed by fluorescence in situ hybridization. Phylogenetic analysis revealed that the magnetococci are affiliated with the Alphaproteobacteria and are most closely related to two uncultured magnetococci with sequence identities of 92.7% and 92.4%, respectively. Because they display a >7% sequence divergence to all bacteria reported, the bean-like magnetococci may represent two novel genera.

Magnetotaxis Enables Magnetotactic Bacteria to Navigate in Flow.

Abstract: Magnetotactic bacteria (MTB) play an important role in Earth's biogeochemical cycles by transporting minerals in aquatic ecosystems, and have shown promise for controlled transport of microscale objects in flow conditions. However, how MTB traverse complex flow environments is not clear. Here, using microfluidics and high-speed imaging, it is revealed that magnetotaxis enables directed motion of Magnetospirillum magneticum over long distances in flow velocities ranging from 2 to 1260 µm s-1 , corresponding to shear rates ranging from 0.2 to 142 s-1 -a range relevant to both aquatic environments and biomedical applications. The ability of MTB to overcome a current is influenced by the flow, the magnetic field, and their relative orientation. MTB can overcome 2.3-fold higher flow velocities when directed to swim perpendicular to the flow as compared to upstream, as the latter orientation induces higher drag. The results indicate a threshold drag of 9.5 pN, corresponding to a flow velocity of 550 µm s-1 , where magnetotaxis enables MTB to overcome counterdirectional flow. These findings bring new insights into the interactions of MTB with complex flow environments relevant to aquatic ecosystems, while suggesting opportunities for in vivo applications of MTB in microbiorobotics and targeted drug delivery.

Configuration of redox gradient determines magnetotactic polarity of the marine bacteria MO‐1

Abstract: Summary Magnetotactic bacteria are capable of aligning and swimming along the geomagnetic field lines; such a behaviour is called magnetotaxis. Previous studies reported that bacteria in the northern hemisphere migrate preferentially towards the North Pole of the Earth's magnetic field (north-seeking, NS), whereas those in the southern hemisphere swim towards the South Pole (south-seeking, SS). The orientated swimming is thought to guide bacteria migrating downward to the favourable microaerobic or anaerobic regions in stratified water column or sediments. Recent identification of SS populations in northern hemisphere challenged the model of the adaptive value of magnetotaxis. To seek explanation for the apparent discrepancy, we analysed magnetotaxis polarity of axenic cultures under simulated growth conditions in hypomagnetic, northern-hemisphere-like or southern-hemisphere-like magnetic fields. We found that NS and SS cells could obviously coexist in hypomagnetic field and even, when the oxidation-reduction gradient configuration is suitable, in the geomagnetic field. These results reveal the selectivity of the redox gradient configuration on magnetotactic polarity of the cells and reconcile the discrepancy of the early reports.

A new dimension to sediment magnetism: Charting the spatial variability of magnetic properties across lake basins

Abstract: We have investigated the variability of the magnetic properties of surface sediments across eight Minnesota lake basins. The measured magnetic properties are controlled by the competing fluxes of allochthonous and autochthonous magnetic particles, and differ according to location in the basin. Shoreline sediments are dominated by detrital magnetic particles, whereas littoral and profundal sediments are characterized by a combination of bacterial magnetosomes and detrital particles. The position of the oxic–anoxic interface, which may occur in the water or within the sediment column, controls the depth at which living magnetotactic bacteria occur, and determines the degree of preservation of their magnetosome chains in the surface sediment. The preservation potential of undisturbed chains is higher for bacterial magnetite formed at the top of the sediment column in the littoral area than for magnetosomes originating in the water column in the profundal area. Bacterial magnetite in the profundal facies will contain a higher proportion of chains collapsed during settlement through the water column to the lake bottom. This process increases the fraction of interacting magnetosomes, which in turn artificially lowers the ARM ratio (χ ARM /IRM), which ceases to be a reliable grain size indicator in the profundal environment. Our results indicate that a holistic approach to interpreting limnologically-derived paleoecological data should be employed. Specifically, a thorough understanding of evolving and interrelated factors such as basin morphology and limnologic conditions is crucial for a more confident interpretation of the sedimentary record in terms of environmental conditions at the time of sediment deposition.