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Magnetotactic bacteria

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


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TL;DR: Transmission electron and scanning electron microscopy were used for morphological study of MTB and energy dispersive analysis of X-rays and vibrating sample magnetometer techniques were used to elucidate the phase and magnetization in the bacterially synthesized magnetosomes.
Abstract: Magnetotactic bacteria (MTB), Magnetospirillum magnetotacticum (MS-1) were successfully grown in modified magnetic spirillum growth medium (MSGM) at normal laboratory environment. About five-time increase in the bacterial yield was achieved in the modified MSGM medium without compromising their magnetosomes properties. Transmission electron and scanning electron microscopy (TEM & SEM) were used for morphological study of MTB. Energy dispersive analysis of X-rays (EDAX) and vibrating sample magnetometer (VSM) techniques, respectively, were used to elucidate the phase and magnetization in the bacterially synthesized magnetosomes. These studies were important to cross-check the morphology of magnetosomes, as the formation of magnetosomes was highly sensitive to environmental conditions.

14 citations

Journal ArticleDOI
TL;DR: In this article, an easy green synthesis route in a thermoreversible gelatin hydrogel matrix is used for the synthesis and detailed characterization of ferrimagnetic magnetite chain-like assemblies.
Abstract: Inspired by chains of ferrimagnetic nanocrystals (NCs) in magnetotactic bacteria (MTB), the synthesis and detailed characterization of ferrimagnetic magnetite NC chain-like assemblies is reported. An easy green synthesis route in a thermoreversible gelatin hydrogel matrix is used. The structure of these magnetite chains prepared with and without gelatin is characterized by means of transmission electron microscopy, including electron tomography (ET). These structures indeed bear resemblance to the magnetite assemblies found in MTB, known for their mechanical flexibility and outstanding magnetic properties and known to crystallographically align their magnetite NCs along the strongest magnetization easy axis. Using electron holography (EH) and angular dependent magnetic measurements, the magnetic interaction between the NCs and the generation of a magnetically anisotropic material can be shown. The electro- and magnetostatic modeling demonstrates that in order to precisely determine the magnetization (by means of EH) inside chain-like NCs assemblies, their exact shape, arrangement and stray-fields have to be considered (ideally obtained using ET).

14 citations

Journal ArticleDOI
TL;DR: It was shown that some protozoa inhabiting this niche could become magnetic by the ingestion of magnetic crystals biomineralized by grazed MTB, and this study shows that magnetic MTB grazers are commonly observed in marine and freshwater sediments and can sometimes accumulate very large amounts of particulate iron.
Abstract: Magnetotactic bacteria (MTB) represent a group of microorganisms that are widespread in aquatic habitats and thrive at oxic-anoxic interfaces. They are able to scavenge high concentrations of iron thanks to the biomineralization of magnetic crystals in their unique organelles, the so-called magnetosome chains. Although their biodiversity has been intensively studied, their ecology and impact on iron cycling remain largely unexplored. Predation by protozoa was suggested as one of the ecological processes that could be involved in the release of iron back into the ecosystem. Magnetic protozoa were previously observed in aquatic environments, but their diversity and the fate of particulate iron during grazing are poorly documented. In this study, we report the morphological and molecular characterizations of a magnetically responsive MTB-grazing protozoan able to ingest high quantities of MTB. This protozoan is tentatively identified as $Uronema\ marinum$, a ciliate known to be a predator of bacteria. Using light and electron microscopy, we investigated in detail the vacuoles in which the lysis of phagocytized prokaryotes occurs. We carried out high-resolution observations of aligned magnetosome chains and ongoing dissolution of crystals. Particulate iron in the ciliate represented approximately 0.01% of its total volume. We show the ubiquity of this interaction in other types of environments and describe different grazing strategies. These data contribute to the mounting evidence that the interactions between MTB and protozoa might play a significant role in iron turnover in microaerophilic habitats.

14 citations

Journal ArticleDOI
TL;DR: It is demonstrated that a significantly higher voltage than that of the control could be measured when MTB or purified magnetosomes were pumped through a solenoid by applying Faraday's law of electromagnetic induction.
Abstract: Table S1. Voltage measured from the uninoculated medium, MTB culture and purified magnetosomes respectively.

14 citations

Journal ArticleDOI
21 May 2019-Mbio
TL;DR: Ferritin-like proteins are not involved in magnetite biomineralization and Bfr-bound ferrihydrite is not a precursor of magnetite biosynthesis, and the unique properties of so-far-uncharacterized heterooligomeric bacterioferritins are revealed.
Abstract: The biomineralization pathway of magnetite in magnetotactic bacteria is still poorly understood and a matter of intense debates. In particular, the existence, nature, and location of possible mineral precursors of magnetite are not clear. One possible precursor has been suggested to be ferritin-bound ferrihydrite. To clarify its role for magnetite biomineralization, we analyzed and characterized ferritin-like proteins from the magnetotactic alphaproteobacterium Magnetospirillum gryphiswaldense MSR-1, employing genetic, biochemical, and spectroscopic techniques. Transmission Mossbauer spectroscopy of the wild type (WT) and a bacterioferritin (bfr) deletion strain uncovered that the presence of ferrihydrite in cells is coupled to the presence of Bfr. However, bfr and dps deletion mutants, encoding another ferritin-like protein, or even mutants with their codeletion had no impact on magnetite formation in MSR-1. Thus, ferritin-like proteins are not involved in magnetite biomineralization and Bfr-bound ferrihydrite is not a precursor of magnetite biosynthesis. Using transmission electron microscopy and bacterial two-hybrid and electrophoretic methods, we also show that MSR-1 Bfr is an atypical representative of the Bfr subfamily, as it forms tetraeicosameric complexes from two distinct subunits. Furthermore, our analyses revealed that these subunits are functionally divergent, with Bfr1 harboring a ferroxidase activity while only Bfr2 contributes to heme binding. Because of this functional differentiation and the poor formation of homooligomeric Bfr1 complexes, only heterooligomeric Bfr protects cells from oxidative stress in vivo. In summary, our results not only provide novel insights into the biomineralization of magnetite but also reveal the unique properties of so-far-uncharacterized heterooligomeric bacterioferritins.IMPORTANCE Magnetotactic bacteria like Magnetospirillum gryphiswaldense are able to orient along magnetic field lines due to the intracellular formation of magnetite nanoparticles. Biomineralization of magnetite has been suggested to require a yet-unknown ferritin-like ferrihydrite component. Here, we report the identification of a bacterioferritin as the source of ferrihydrite in M. gryphiswaldense and show that, contrary to previous reports, bacterioferritin is not involved in magnetite biomineralization but required for oxidative stress resistance. Additionally, we show that bacterioferritin of M. gryphiswaldense is an unusual member of the bacterioferritin subfamily as it is composed of two functionally distinct subunits. Thus, our findings extend our understanding of the bacterioferritin subfamily and also solve a longstanding question about the magnetite biomineralization pathway.

14 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202339
202288
202137
202061
201950
201873