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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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Journal ArticleDOI
23 Dec 2011-Science
TL;DR: Genomic analysis of strain BW-1 reveals the presence of two different magnetosome gene clusters, suggesting that one may be responsible for greigite biomineralization and the other for magnetite, a previously unknown group of sulfate-reducing bacteria in the Deltaproteobacteria.
Abstract: Magnetotactic bacteria contain magnetosomes—intracellular, membrane-bounded, magnetic nanocrystals of magnetite (Fe3O4) or greigite (Fe3S4)—that cause the bacteria to swim along geomagnetic field lines. We isolated a greigite-producing magnetotactic bacterium from a brackish spring in Death Valley National Park, California, USA, strain BW-1, that is able to biomineralize greigite and magnetite depending on culture conditions. A phylogenetic comparison of BW-1 and similar uncultured greigite- and/or magnetite-producing magnetotactic bacteria from freshwater to hypersaline habitats shows that these organisms represent a previously unknown group of sulfate-reducing bacteria in the Deltaproteobacteria. Genomic analysis of BW-1 reveals the presence of two different magnetosome gene clusters, suggesting that one may be responsible for greigite biomineralization and the other for magnetite.

176 citations

Journal ArticleDOI
03 May 2008-Langmuir
TL;DR: The bacterium Actinobacter sp.
Abstract: The bacterium Actinobacter sp. has been shown to be capable of extracellularly synthesizing iron based magnetic nanoparticles, namely maghemite (γ-Fe2O3) and greigite (Fe3S4) under ambient conditions depending on the nature of precursors used. More precisely, the bacterium synthesized maghemite when reacted with ferric chloride and iron sulfide when exposed to the aqueous solution of ferric chloride-ferrous sulfate. Challenging the bacterium with different metal ions resulted in induction of different proteins, which bring about the specific biochemical transformations in each case leading to the observed products. Maghemite and iron sulfide nanoparticles show superparamagnetic characteristics as expected. Compared to the earlier reports of magnetite and greigite synthesis by magnetotactic bacteria and iron reducing bacteria, which take place strictly under anaerobic conditions, the present procedure offers significant advancement since the reaction occurs under aerobic condition. Moreover, reaction end p...

172 citations

Journal ArticleDOI
TL;DR: The novel use of magnetic particles isolated from magnetotactic bacteria collected from enriched sludge by use of a magnetic harvesting apparatus and glucose oxidase and uricase coupled with biogenic magnetic particles retained their activities when they were reused 5 times.
Abstract: We report the novel use of magnetic particles isolated from magnetotactic bacteria. Magnetotactic bacteria were collected from enriched sludge by use of a magnetic harvesting apparatus. Magnetic particles separated from magnetotactic bacteria were shown to be pure magnetite. Glucose oxidase and uricase were immobilized on magnetic particles. The activity of glucose oxidase immobilized on biogenic magnetites was 40 times that immobilized on artificial magnetites or Zn-ferrite particles. Both glucose oxidase and uricase coupled with biogenic magnetic particles retained their activities when they were reused 5 times.

170 citations

Journal ArticleDOI
08 Apr 1987-Nature
TL;DR: In this article, the formation of fine-grained authigenic magnetites near the commonly observed brown-tan-green colour boundary, which marks the transition from Fe-oxidizing to Fe-reducing conditions, was investigated.
Abstract: The resolution and reliability of magnetostratigraphy and reconstructed time series of geomagnetic field behaviour depend critically on where remanence is acquired and fixed in the sediment column and whether the magnetization is altered chemically after deposition. If authigenic magnetic minerals are formed at depth or if the magnetic carriers are changed after deposition, then the nature and timing of magnetic events can be affected by depth offsets in remanence acquisition and mixing of detrital and authigenic signals. Using palaeo- and rock-magnetic and sediment geochemical analyses, we have studied how early diagenesis affects the magnetic properties of suboxic hemipelagic sediments. Here, we report evidence of the formation of fine-grained authigenic magnetites near the commonly observed brown–tan-green colour boundary, which marks the transition from Fe-oxidizing to Fe-reducing conditions. We propose that biogenic magnetite, produced by magnetotactic bacteria, forms as part of the microbially mediated sequence of reactions involved in the oxidation of organic matter. The magnetite is created as a metabolic by-product of the microorganisms' use of iron redox transitions as a source of energy. Active magnetite formation appears to be restricted to a zone between the levels of nitrate and iron reduction.

170 citations

Journal ArticleDOI
TL;DR: Magnetite nanocrystals are synthesized in the presence of a recombinant Mms6 protein thought to be involved in the biomineralization of bacterial magnetite magnetosomes, the mammalian iron-storage protein, ferritin, and two proteins not known to bind iron, lipocalin (Lcn2) and bovine serum albumin (BSA) as mentioned in this paper.
Abstract: Magnetite nanocrystals are synthesized in the presence of a recombinant Mms6 protein thought to be involved in the biomineralization of bacterial magnetite magnetosomes, the mammalian iron-storage protein, ferritin, and two proteins not known to bind iron, lipocalin (Lcn2) and bovine serum albumin (BSA). To mimic the conditions at which magnetite nanocrystals are formed in magnetotactic bacteria, magnetite synthesis is performed in a polymeric gel to slow down the diffusion rates of the reagents. Recombinant Mms6 facilitates formation of ca. 30 nm single-domain, uniform magnetite nanocrystals in solution, as verified by using transmission electron microscopy analysis and magnetization measurements. The nanocrystals formed in the presence of ferritin, Lcn2, and BSA, do not exhibit the uniform sizes and shapes observed for those produced in the presence of Mms6. Mms6-derived magnetite nanoparticles show the largest magnetization values above the blocking temperature, as well as the largest magnetic susceptibility compared to those of the nanomaterials synthesized with other proteins. The latter is indicative of a substantial effective magnetic moment per particle, which is consistent with the presence of magnetite with a well-defined crystalline structure. The combination of electron microscopy analysis and magnetic measurements confirms our hypothesis that Mms6 promotes the shape-selective formation of uniform superparamagnetic nanocrystals. This provides a unique bioinspired route for synthesis of uniform magnetite nanocrystals.

168 citations


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