Showing papers on "Magnetotactic bacteria published in 1990"
TL;DR: In this paper, the ability of magnetotactic bacteria to orientate and navigate along geomagnetic field lines is due to the controlled intracellular deposition of the iron oxide mineral, magnetite (Fe3O4)1,2.
Abstract: THE ability of magnetotactic bacteria to orientate and navigate along geomagnetic field lines is due to the controlled intracellular deposition of the iron oxide mineral, magnetite (Fe3O4)1,2. The function and crystal chemical specificity of this mineral has been considered to be unique amongst the prokaryotes3. Moreover, the bacterial production of magnetite may represent a significant contribution to the natural remanent magnetism of sediments4,5. Here we report, the intracellular biomineralization of single crystals of the ferrimagnetic iron sulphide, greigite (Fe3S4), in a multicellular magnetotactic bacterium common in brackish, sulphide-rich water and sediment. We show that these crystals are often aligned in chains and associated with single crystals of the non-magnetic mineral, iron pyrite (FeS2). Our results have important implications for understanding biomineralization processes and magnetotaxis in micro-organisms inhabiting sulphidic environments. Furthermore, the biogenic production of magnetic iron sulphides should be considered as a possible source of remanent magnetization in sediments.
419 citations
TL;DR: In this article, the discovery of magnetic iron-sulphur crystals in a highly motile multicellular aggregate of bacteria found in brackish water with sulphide-rich sediments was reported.
Abstract: IN all magnetotactic microorganisms studied so far, the geomagnetic field is detected by magnetic particles with a permanent magnetic moment. These are crystallites enveloped by a membrane that forms the magnetosome, a specialized organelle common to magnetotactic cells1,2. To date, the magnetic crystallite of magnetotactic bacteria has been found to be magnetite, an iron-oxygen mineral3–7. Here we report the discovery of magnetic iron-sulphur crystals in a highly motile multicellular aggregate of bacteria found in brackish water with sulphide-rich sediments. The iron sulphide crystals are enveloped by amorphous or weakly crystalline regions rich in iron and oxygen, and these regions are surrounded by a membrane forming the magnetosome. The oxygen-rich region may be involved in growth of the iron sulphide crystals. The magnetosomes are found in planar groups inside the cytoplasm of each cell in the aggregate. Magnetic iron sulphide such as we describe here, which is probably pyrrhotite, may be a source of remnant magnetization in sediments and soils.
247 citations
TL;DR: The presence of intracellular greigite crystals in two different types of rod-shaped single-celled magnetotactic bacteria collected from sulfide-rich sites is reported.
Abstract: We report the presence of intracellular greigite crystals in two different types of rod-shaped single-celled magnetotactic bacteria collected from sulfide-rich sites
138 citations
TL;DR: There are many commercial uses of the minute permanent magnets of magnetotactic bacteria, such as in the manufacture of magnetic tape and magnetic printing inks, and its biotechnological applications.
Abstract: Publisher Summary The chapter introduces magnetotactic bacteria and discusses its occurrence in the nature and methods applied for studying them. The structure and the physiology of the bacteria is also discussesd. The processes of magnetite biomineralization in magnetotactic bacteria are reviewed. The structural, morphological, and crystal growth properties of the magnetite inclusions are described and proposed mechanisms of biomineralization are discussed. Magnetotatic bacteria exhibit magnetotaxis as a consequence of magnetite inclusions in their cells. Palaeomagnetism is a marked phylogenetic diversity within this group of organisms. These organisms provide clues about geochemical changes in the earth's atmosphere. Although there are several magnetic minerals, the most observed and magnetically stable phase in these sediments is magnetite. The chapter also discusses its biotechnological applications. There are many commercial uses of the minute permanent magnets of magnetotactic bacteria, such as in the manufacture of magnetic tape and magnetic printing inks.
128 citations
TL;DR: The presence of dissimilatory iron reducing bacteria, however, can be detected using microbiological techniques and sediment geochemistry as discussed by the authors, but it is not generally appreciated that magnetotactic bacteria and their magnetofossils can be identified by the unusual morphologies, size range, and composition of the magnetite crystals.
Abstract: Biogenic magnetites are produced through the reduction of ferric iron by both biologically induced (extracellular) and biologically controlled (intracellular) processes. With few exceptions, all are ultra-fine-grained, single-domain magnetite. Biogenic magnetites formed by magnetotactic bacteria (biologically controlled) have been shown to contribute significantly to the natural remanent magnetization of carbonates and limestones, hemipelagic and deep-sea marine sediments. The input into sediments of ultra-fine-grained magnetite produced by dissimilatory iron reducing bacteria (biologically induced) has yet to be firmly established but may be even more significant. Whether either type of authigenic biomagnetite is preserved is determined by postdepositional factors including oxidation, reduction by substitution, and dissolution. Unconsolidated and lithified sediments can be screened for putative biogenic magnetite by rock magnetic techniques. It is not generally appreciated that magnetotactic bacteria and their magnetofossils can be identified by the unusual, and in some cases unique, morphologies, size range, and composition of the magnetite crystals. Magnetite produced by dissimilatory iron reducing bacteria have a distinctive morphology and size range, but it is currently controversial as to whether these can be distinguished from certain chemically precipitated magnetites. The presence of dissimilatory iron reducing bacteria, however, can be detected using microbiological techniques and sediment geochemistry. Biogenic magnetites are trace fossils and potentially useful environmental indicators and are considered to have significant input to the magnetization of most sediments, both modern and ancient.
78 citations
TL;DR: The detection of mouse IgG was carried out using FITC (fluorescein-isothiocyanate) conjugated anti-mouse-IgG immobilized on bacterial magnetites and a flow injection system with a fluorescence spectrophotometer.
Abstract: Isolated helical magnetotactic bacteria were cultured in a medium containing succinate, nitrate, and ferric malate as carbon, nitrogen, and iron sources, respectively The magnetotactic bacteria could grow aerobically The cells which grew aerobically had oxidase activity An initial inoculum of 10/sup 5/ cells/ml was used Stationary phase was reached 14*10/sup 9/ cells/ml after 4-5 days growth When the cells were disrupted using ultrasonication, 26-mg bacterial magnetites were obtained from a 1-l culture of magnetotactic bacteria The detection of mouse IgG was carried out using FITC (fluorescein-isothiocyanate) conjugated anti-mouse-IgG immobilized on bacterial magnetites and a flow injection system with a fluorescence spectrophotometer Relative fluorescence intensity correlated linearly with the concentration of mouse IgG in the range 05-100 ng/ml, and the measurements were established within 2 min using this system >
63 citations
TL;DR: In this paper, the authors identified three species of magnetotactic bacteria from sulphidic environments which contain crystals of the mixed valence ferrimagnetic iron sulphide, greigite (Fe3S4).
Abstract: Several species of aquatic bacteria are known to exploit the earth’s geomagnetic field as a means of directing their motion towards suitable habitats. A feature common to these bacteria is the presence of discrete intracellular magnetic inclusions, magnetosomes, aligned in chains along the long axis of the organism. The size and orientation of the individual magnetic particles imparts a permanent magnetic dipole moment to the cell which is, in turn, responsible for the magnetotactic response. In all species examined to date the magnetic particles have been found to be well-ordered, single domain, membrane-bounded crystals with reproducible, species-specific morphologies. Until recently, however, only crystals of the mixed valence iron oxide, magnetite (Fe3O4), were identified in these magnetotactic bacteria. We have now identified three species of bacteria from sulphidic environments which contain crystals of the mixed valence ferrimagnetic iron sulphide, greigite (Fe3S4). High resolution electron microscopical studies of the biogenic greigite crystals showed that they also exhibit the narrow size range (50-90nm) and unique crystallographic habits (e.g. cubo-octahedral, rectangular prismatic) which characterized and distinguished the inclusions in other magnetotactic species. Thus, it would appear that the bio-precipitation of iron sulphides in magnetotactic bacteria is a highly regulated process which is directed and controlled at the molecular level. These findings are not only important to our understanding of biomineralization in unicellular organisms but may also be significant to studies of paleomagnetism. Furthermore, the controlled synthesis of greigite presents an interesting challenge to material scientists and solid state chemists.
34 citations
17 Dec 1990
TL;DR: Three habitats local to Durham were selected for this work; Mill Pond, a freshwater eutrophic pond draining Oyster River into Great Bay estuary, the estuary and a marine coastal saltmarsh in which the authors have found large populations of sulfide-type magnetic bacteria.
Abstract: : Three habitats local to Durham were selected for this work; Mill Pond, a freshwater eutrophic pond draining Oyster River into Great Bay estuary, the estuary, and a marine coastal saltmarsh in which we have found large populations of sulfide-type magnetic bacteria. Data being sought will enable the first systematic comparison among marine, estuarine and freshwater habitats of seasonal and vertical distribution of natural populations of magnetotactic bacteria. Enrichments and pure cultures of faculative and obligate iron-reducing bacteria from these diverse environments have been made and are still in progress. To date, new strains of iron reducing bacteria, some of which may be magnetogenic, have been isolated but these have not been characterized.
1 citations
TL;DR: The magnetosomes of magnetotactic bacteria are intracytoplasmic membrane-bound particles of magnetite, Fe 3 O 4, which are within the single-domain size range (∼500 A) of the magnetite.
Abstract: In 1975, Blakemore discovered the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum which navigates along the magnetic-field direction. Electron microscopic work showed that the magnetotactic bacteria contain magnetosomes which are intracytoplasmic membrane-bound particles of magnetite, Fe 3 O 4 . The magnetosomes are within the single-domain size range (∼500 A) of Fe 3 O 4 . The magnetosomes within cells are often arranged in one or more chains with the chain axis more or less parallel to the axis of motility of the cell. A detailed study of the magnetic properties of magnetotactic bacteria can be found in the paper by Moskowitz.
17 Apr 1990
TL;DR: This mass culture of magnetotactic bacteria is succeeded to obtain a large quantity of bacterial magnetites and measured mouse IgG concentration by using fluorescein-isothiocyanate (FITC) conjugated anti-mouse IgG immobilized onacterial magnetites.
Abstract: Magnetotactic bacteria which orient and swim along geomagnetic fields have been found in fresh and marine sediments (1,2).