Magnetotactic bacteria

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

South Seeking Magnetic Bacteria from Lonar Lake

Abstract: Magnetotactic bacteria (MTB) are known to be major constituents of natural microbial communities in sediments and chemically stratified water columns such as those found in lakes and oceans and typically, such bacteria in the northern hemisphere are known to move to the magnetic South. Because of their potential to accumulate and precipitate iron minerals, these bacteria are assumed to have a great impact on biogeochemical cycling in natural sediments. A broad diversity of morphological forms of these bacteria with their unique character ofmagnetosomes' are today known and they have generated tremendous interest among microbiologists and biotechnologists as well as other interdisciplinary researchers. The Lonar Lake, formed in a meteorite impact crater in the Buldhana District of Maharashtra is a closed basin lake and is a unique environment characterized by high alkalinity (pH 9.5 - 10.0, CaCO3 alkalinity - 3.6 g/L) and salinity. Evidences of magnetic activity in the surrounding rocks and soil are also found. Several studies on the microbial biodiversity of this environment have been carried out previously but there are no reports of magnetotactic bacteria. This study reports the isolation and characterization of such magnetotactic bacteria from the sediments along the littoral zone of the Lonar Lake. The bacteria isolated bymagnetic collection' and thecapillary racetrack' methods were found to be predominantly rods with some coccoidal forms. Their response to a magnetic field was observed employing thehanging drop' technique under a microscope and the use of a semisolid medium. The bacteria showed a typical response in the form of movement towards the South Pole of the magnet and precise alignment at the edge of the hanging drop. Further studies on their characters and confirmation of the accumulation of intracellular magnetosomes are in progress.

Separation of Ferromagnetic Components by Analyzing the Hysteresis Loops of Remanent Magnetization

Abstract: The new method is suggested for separating ferromagnetic components in sediments through analyzing the coercivity spectra of the samples by the continuous wavelet transform with the Gaussian-based wavelet (MHAT). A total of 1056 samples of Lake Khuvsgul’s sediments (Mongolia) are studied. At least four groups of magnetic components are identified based on the analysis of their magnetization and remagnetization curves. Almost all samples are found to contain two components of bacterial origin which are represented by the assemblages of the interacting single-domain grains and differ by the grain compositions (magnetite and greigite). The applicability of the magnetic data for diagnosing magnetotactic bacteria in sediments and building paleoecological and paleoclimatic reconstructions is demonstrated.

Genomic evidence of the illumination response mechanism and evolutionary history of magnetotactic bacteria within the Rhodospirillaceae family.

Abstract: Magnetotactic bacteria (MTB) are ubiquitous in natural aquatic environments. MTB can produce intracellular magnetic particles, navigate along geomagnetic field, and respond to light. However, the potential mechanism by which MTB respond to illumination and their evolutionary relationship with photosynthetic bacteria remain elusive. We utilized genomes of the well-sequenced genus Magnetospirillum, including the newly sequenced MTB strain Magnetospirillum sp. XM-1 to perform a comprehensive genomic comparison with phototrophic bacteria within the family Rhodospirillaceae regarding the illumination response mechanism. First, photoreceptor genes were identified in the genomes of both MTB and phototrophic bacteria in the Rhodospirillaceae family, but no photosynthesis genes were found in the MTB genomes. Most of the photoreceptor genes in the MTB genomes from this family encode phytochrome-domain photoreceptors that likely induce red/far-red light phototaxis. Second, illumination also causes damage within the cell, and in Rhodospirillaceae, both MTB and phototrophic bacteria possess complex but similar sets of response and repair genes, such as oxidative stress response, iron homeostasis and DNA repair system genes. Lastly, phylogenomic analysis showed that MTB cluster closely with phototrophic bacteria in this family. One photoheterotrophic genus, Phaeospirillum, clustered within and displays high genomic similarity with Magnetospirillum. Moreover, the phylogenetic tree topologies of magnetosome synthesis genes in MTB and photosynthesis genes in phototrophic bacteria from the Rhodospirillaceae family were reasonably congruent with the phylogenomic tree, suggesting that these two traits were most likely vertically transferred during the evolution of their lineages. Our new genomic data indicate that MTB and phototrophic bacteria within the family Rhodospirillaceae possess diversified photoreceptors that may be responsible for phototaxis. Their genomes also contain comprehensive stress response genes to mediate the negative effects caused by illumination. Based on phylogenetic studies, most of MTB and phototrophic bacteria in the Rhodospirillaceae family evolved vertically with magnetosome synthesis and photosynthesis genes. The ancestor of Rhodospirillaceae was likely a magnetotactic phototrophic bacteria, however, gain or loss of magnetotaxis and phototrophic abilities might have occurred during the evolution of ancestral Rhodospirillaceae lineages.

Methods to Study Magnetotactic Bacteria and Magnetosomes

Abstract: Magnetotactic bacteria (MTB) are microorganisms capable of directed migration along geomagnetic field lines due to the presence of magnetosomes (MS) in the cells. Because of the special structures of MS consisting of lipid membranes and crystalline magnetic minerals, MTB have implications for environmental magnetism, development of magnetic materials, and iron biomineralization. Additionally, MS have potential uses for applications in modern biomedicine. Therefore, they have attracted attention from researchers in different disciplines, and various investigated technologies have been explored. Here, we describe methods to study MTB and MS, including enrichment, isolation, phylogenetic diversity, and magnetisms of MTB, and extraction and formation of MS.

Molecular Mechanism of Magnetic Crystal Formation in Magnetotactic Bacteria

Abstract: Magnetotactic bacteria are a group of microorganism producing nano-sized magnetic particles. The bacterial cells accumulate a large amount of iron ion from aquatic environment and synthesize single-crystal magnetic nano-particles under ambient conditions. The size, shape, and composition of the magnetic nano-particles are precisely regulated in individual bacterial cell types. Thus, the understanding of molecular mechanism should provide ideas to design and create magnetic nano-materials with environmentally friendly synthetic routes. This chapter describes the molecular mechanism of magnetic nano-particle formation that has been clarified based on comprehensive molecular analyses of magnetotactic bacteria. Identified proteins from the basic studies are shown to be available for the development of novel magnetic nano-materials. The strategy and fundamental technologies that are useful for the understanding of biomineralization mechanisms are also introduced.