Showing papers on "Magnetotactic bacteria published in 2000"
TL;DR: Six properties of magnetite produced by biologically controlled mechanisms (e.g., magnetotactic bacteria), properties that, collectively, are not observed in any known population of inorganic magnetites are described.
269 citations
Book•
01 Jan 2000
TL;DR: This work focuses on the characterization of the magnetosome Membrane in Magnetospirillium gryphiswaldense, a type of prokaryotes related to Eukaryotes, and its role in biomineralization.
Abstract: Preface. List of Contributors. Abbreviations. Biominerals--An Introduction (E. Baeuerlein). Prokaryotes. Mechanistic Routes to Biomineral Surface Development (D. Fortin, T.J. Beveridge). Magnetic Iron Oxide and Iron Sulfide Minerals within Microorganisms (D.A. Bazylinski, R.B. Frankel). Phylogeny and in Situ Identification of Magnetotactic Bacteria (R. Amann, et al.). Single Magnetic Crystals of Magnetite (Fe 3 O 4 Synthesized in Intracytoplasmic Vesicles of Megnetospirilum gryphiswaldense (E. Baeuerlein). Applications for Magnetosomes in Medical Research (R.C. Reszka). Enzymes for Magnetite Synthesis in Magnetospirillum magnetotacticum (Y. Fukumori). Characterization of the Magnetosome Membrane in Magnetospirillium gryphiswaldense (D. Schuler). Molecular and Biotechnological Aspects of Bacterial Magnetite (T. Matsunaga, T. Sakaguchi). Eukaryotes. A Grand Unified Theory of Biomineralization (J.L. Kirschvink, J.W. Hagadorn). The Biochemistry of Silica Formation in Diatoms (N. Kroger, M. Sumper). Silicic Acid Transport and Its Control During Cell Wall Silicification in Diatoms (M. Hildebrand). The Nanostructure and Development of Diatom Biosilica (R. Wetherbee, et al.). The Biological and Biomimetic Synthesis of Silica and Other Polysiloxanes (K. Shimizu, D.E. Morse). Protein Components and Inorganic Structure in Shell Nacre (A.M. Belcher, E.E. Gooch). Polyanions in the CaCo 3 Mineralization of Coccolithophores (M.E. Marsh). The Calcifying Vesicle Membrane of the Coccolithophore, Pleurochrysis sp (E.L. Gonzales). Index.
183 citations
TL;DR: The protists described here could play a significant role in iron cycling in chemically stratified anoxic basins, either through endogenous production of magnetic iron oxide and/or iron sulfide particles, or by ingestion of magnetotactic bacteria and the subsequent reduction and dissolution of iron oxide/sulfide particles in their magnetosomes.
64 citations
01 Jan 2000
TL;DR: The most widely recognized example of magnetosome production by the magnetotactic bacteria is magnetite biomineralization as discussed by the authors, which is an example of biologically induced mineralization.
Abstract: This chapter examines and reviews features of biologically induced mineralization (BIM)- and biologically controlled mineralization (BCM)-type magnetic particles. It describes microorganisms that produce magnetic minerals (focusing mainly on the magnetotactic bacteria) and also describes the biomineralization processes involved in the synthesis of magnetic minerals. The chapter also reviews the physics and function of magnetotaxis in light of recent findings. In the microbial world, the most widely recognized example of BCM is magnetosome production by the magnetotactic bacteria. Although all freshwater magnetotactic bacteria synthesize magnetite as the mineral phase of their magnetsomes, many marine, estuarine, and salt marsh species produce an iron sulfide-type magnetosome which consists primarily of the magnetic iron sulfide greigite. The chapter discusses stoichiometry changes and specifically whether iron can be replaced with other transition metal ions and whether sulfur and oxygen can replace each other as the nonmetal component in the magnetosome mineral phase. The fact that many higher creatures biomineralize single-magnetic-domain magnetite crystals of similar morphologies suggests the intriguing idea that all these organisms have the same or a similar set of genes responsible for magnetite biomineralization that would probably have originated in the magnetotactic bacteria. Thus, studying how magnetotactic bacteria biomineralize magnetite might have a scientific impact far beyond the studies of microbiology and geology.
44 citations
TL;DR: Magnetotactic bacteria from aquatic environments were analyzed with the electron spectroscopic imaging technique as discussed by the authors, and the number, size, and morphology of magnetosomes, as well as their ultrastructural spatial disposition inside the bacterial cell, could be directly observed and associated with the disposition of flagella of respective cells.
Abstract: Magnetotactic bacteria from aquatic environments were analyzed with the electron spectroscopic imaging technique. Rod-shaped bacteria and cocci were present in most of the samples observed. Magnetotactic multicellular aggregates were also observed at some of the sampling sites. The use of electron spectroscopic imaging allowed the observation of magnetosomes inside magnetotactic microorganisms with exceptional clarity. The number, size, and morphology of magnetosomes, as well as their ultrastructural spatial disposition inside the bacterial cell, could be directly observed and associated with the disposition of flagella of the respective cells.This allowed us to examine the structural relationships between magnetosomes and flagella, which are important components in the mechanisms of magnetotaxis. In disrupted magnetotactic multicellular aggregates, connections between cells were also visualized. We believe this technique will be useful in studying not only magnetotactic bacteria but also other uncultured microorganisms from natural environments.
30 citations
TL;DR: To resolve if gravity influences magnetotactic behavior in bacteria, Magnetospirillum magnetotactum was used to examine magnetotaxis in the absence of gravity and the disappearance of aggregated magnetosomes seemed to correlate with a general loss of cellular integrity in microgravity.
9 citations
Journal Article•
TL;DR: In this article, the composition, microstructure, sizes and habits of magnetite particles from a helicoid magnetotactic bacterium from Gyongyos stream, Szombathely were studied using transmission electron microscopy.
Abstract: Magnetotactic bacteria produce nano-scale, intracellular magnetic minerals. The study of such minerals is of interest because it can shed light on biogenic mineral-forming processes, and on the potential contribution of biomagnets to the magnetic signal of sediments and rocks. We collected sediment and water samples from several Hungarian lakes and streams. Magnetotactic bacteria were present in all studied environments; in some samples they occurred in such large numbers that their mineral inclusions likely represent a major source for sediment magnetism. After magnetic enrichment of magnetotactic species, we characterized distinct morphological types using a light microscope. Our systematic study showed that a few bacterium types are widespread in most of the studied freshwater environments. Using transmission electron microscopy, we studied the composition, microstructure, sizes and habits of magnetite particles from a helicoid magnetotactic bacterium from Gyongyos stream, Szombathely. Size and shape distributions of the intracellular crystals show some distinct features that may be used for distinguishing bacterial from nonbiogenic magnetite and for identifying possible mechanisms of crystal growth. In particular, the crystal size distribution (CSD) curve is highly asymmetric, consistently with previous observations on magnetite from magnetotactic bacteria. The asymmetry and our new observation of two maxima in the CSD suggest that Ostwald ripening and crystal agglomeration played important roles in the formation of the nanoscale magnetite particles.
7 citations
TL;DR: Zhang et al. as mentioned in this paper found that magnetotactic bacteria (MB) and magnetosomes (MS) in Chinese loess-paleosol sequences are associated with the environment in which MB live.
Abstract: 405 samples were collected from L5-S5-L6 in consideration of obvious variations in susceptibility of the geological sections, which are section Xifeng in Gansu Province and section Duanjiapo in Shaanxi Province for study of magnetotactic bacteria (MB) and magnetosomes (MS) in Chinese loess-paleosol sequences MB in each sample were observed by TEM after being cultured under 8–18°C, room temperature (RT), 25°C, 26°C and 30°C conditions In general, MB are distributed widely in loess-paleosol sequences, fewer in loess layers with predomination of vibriod in shape However, there are more MB in paleosol layers with morphological varieties such as roddish, vibriod and occasionally approximately coccus The magnetosomes (MS) in MB of paleosol are usually arranged in chains along the cells It was also found that MB growth and MS formation are associated with the environment in which MB live It can be inferred from the distributions of MB and MS that the paleoclimates fluctuated during the formation of loess-paleosol sequences in the Chinese Loess Plateau The climate became gradually warmer but displayed more frequent fluctuations from the northwest to the southeast of the Plateau
6 citations
TL;DR: The presence of MscS-like channels in M. magnetotacticum reveals the presence of mechanosensitive channels in this bacterium and provides a model for investigation of the effects of magnetic fields on MS ion channels in magnetite-bearing cells.
Abstract: To determine whether or not mechanosensitive (MS) ion channels are present in the magnetotactic bacterium Magnetospirillum magnetotacticum, techniques for spheroplast preparation in Escherichia coli were adapted for this bacterium. This resulted in the formation of 2–3-μm spheroplasts, which were used for patch clamp analysis. Ion channel activity in M. magnetotacticum was compared with that of the MS of small conductance (MscS) in E. coli. This comparison reveals the presence of MscS-like channels in M. magnetotacticum and, as this bacterium produces intracellular magnetite (Fe3O4) particles similar to those found in the human brain, provides a model for investigation of the effects of magnetic fields on MS ion channels in magnetite-bearing cells.
5 citations
01 Jan 2000
TL;DR: Zhang et al. as discussed by the authors studied magnetotactic bacteria (MB) and magnetosomes (MS) in Chinese loess-paleosol sequences and found that MB growth and MS formation are associated with the environment in which MB live.
Abstract: 405 samples were collected from L5-S5-L6 in consideration of obvious variations in susceptibility of the geological sections, which are section Xifeng in Gansu Province and section Duanjiapo in Shaanxi Province for study of magnetotactic bacteria (MB) and magnetosomes (MS) in Chinese loess-paleosol sequences. MB in each sample were observed by TEM after being cultured under 8-18℃, room temperature (RT), 25℃, 26℃ and 30℃ conditions. In general, MB are distributed widely in loess-paleosol sequences, fewer in loess layers with predomination of vibriod in shape. However, there are more MB in paleosol layers with morphological varieties such as roddish, vibriod and occasionally approximately coccus. The magnetosomes (MS) in MB of paleosol are usually arranged in chains along the cells. It was also found that MB growth and MS formation are associated with the environment in which MB live. It can be inferred from the distributions of MB and MS that the paleoclimates fluctuated during the formation of loess
4 citations
TL;DR: In this article, the motion of a magnetotactic bacterium submitted to an oscillating magnetic field was studied and the nature of the U-turn process, which occurred when the magnetic fields were reversed, was investigated.
Abstract: The motion of a magnetotactic bacterium submitted to an oscillating magnetic field was studied. The nature of the U-turn process, which occurred when the magnetic field was reversed, was investigated. It is analytically shown that this process presents a chaotic behavior. When the magnetic field is reversed the bacterium may decide if the turning will be to the right side or to the left side. Such choice is highly sensitive to the initial conditions, making it impossible to predict which side will be taken in the U-turn.
01 Mar 2000
TL;DR: In this article, the authors use rigorous mathematical modeling to compare ALH84001 prismatic magnetites with those produced by terrestrial magnetotactic bacteria, MV-1, and find that this subset of the Martian magnetites appears to be statistically indistinguishable from those of MV-2.
Abstract: Here we use rigorous mathematical modeling to compare ALH84001 prismatic magnetites with those produced by terrestrial magnetotactic bacteria, MV-1. We find that this subset of the Martian magnetites appears to be statistically indistinguishable from those of MV-1.