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| Brian Lower, Assistant Professor in the School of Environment and Natural Resources, is the lead principal investigator in an National Science Foundation funded project 'Using single-molecule force and fluorenscence microscopy to elucidate the molecular mcehanism of bioinspired magnetite synthesis in magnetotactic bacteria'. |
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MICROBES THAT SYNTHESIZE NANOSIZED COMPASSES TO NAVIGATE THE GLOBE
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Magnetotaxis is believed to be accomplished through the use of internal magnets that act as tiny compasses pointing an organism in the correct direction. The tiniest of these organisms are a group of aquatic microbes called magnetotactic bacteria. These microbes are able to orient themselves in a pond or lake according to Earth’s geomagnetic field by synthesizing nanometer-sized, iron-containing minerals called magnetite (Fe3O4). Each particle is approximately 35-120 nanometers in diameter, meaning that approximately 10-million of these particles would fit within the period at the end of this sentence! Each nanomagnetite particle behaves as tiny magnets with a north pole and south pole. The bacteria arrange the nanomagnetite particles into a chain making one long magnet that functions as a compass allowing the bacteria to align themselves with Earth’s geomagnetic field.
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| It is believed that these nanosized magnets allow the bacteria to swim along Earth’s geomagnetic field towards favorable environments. Oxygen is toxic to these microbes, so they favor habitats with little to no dissolved oxygen (i.e., deeper water or sediment). In the Northern Hemisphere, the geomagnetic north actually points down and at a slight angle, therefore, magnetotactic bacteria follow their nano-sized compass north and swim into deeper water where less oxygen is present. In the Southern Hemisphere its just the opposite, such that the geomagnetic north points up and at an angle. Therefore, in this part of the globe, magnetotactic bacteria follow their compass south to deeper, less oxygenated water. This hypothesis, however, has recently been questioned with the discovery of south-seeking bacteria in the Northern Hemisphere. |
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| While there is still much to learn about these curious bacteria, and magnetotaxis in general, the goal of Prof. Lower’s research is to determine the molecular mechanism by which these microbes use specific protein molecules to synthesize the nano-sized compasses. To accomplish this Dr. Lower has teamed up with Prof. Dennis A. Bazylinski from the University of Nevada, Las Vegas (UNLV), who is a well-respected scientist in the field of biomineralization. Drs. Lower and Bazylinski have just been awarded a three-year $404,000 grant from the National Science Foundation (NSF) to fund their research. This grant will fund several graduate students who will be working on this project, including Lijun Chen (School of Environment and Natural Resources), Lumarie Pérez (School of Environment and Natural Resources), and Zachery Oestreicher (School of Earth Sciences) from The Ohio State University. |
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The PIs will focus their effort on four proteins, called Mms proteins, which they believe are used by the magnetotactic bacteria to synthesize the nanomagnetite. As part of the research, they will develop single-molecule imaging techniques in atomic force and fluorescence microscopy to determine the molecular mechanism for the biomineralization of nanomagnetite crystals in magnetotactic bacteria. They will identify the function(s) of the individual Mms protein molecules involved in the biomineralization process and determine how they control crystal nucleation, growth and morphology, examine the organization of the protein molecules within a bacterial membrane and with respect to nascent Fe3O4 nanoparticles, identify the amino acid sequences within these molecules required for crystal nucleation and growth, and uncover functional protein complexes required for nanomagnetite biomineralization.
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Results from this work will advance knowledge in microbiology, geology, chemistry and environmental science. Understanding how these microorganisms use specific proteins to biomineralize nanomagnetite represents an important paradigm for bioinspired material synthesis used by other organisms, including multi-cellular organisms like fish, birds, and even humans. This knowledge can become a basis for bio-controlled approaches to synthesize tailor-made inorganic nanostructures for applications across a diverse span of technologies including medicine, electronics, and biotechnology.
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By understanding the biomineralization process in magnetotactic bacteria, we might also learn how to determine whether nanomagnetite found in the environment are biogenic in origin. This is especially important in determining the reliability for the use of nanomagnetite particles as biomarkers for past life on Earth as well as in extraterrestrial habitats and materials (e.g., the Martian meteorite ALH84001). Furthermore, the biogeochemical cycling of iron by microorganisms (e.g., the accumulation and conversion of iron into Fe3O4 by magnetotactic bacteria) is of particular importance because iron is a ubiquitous and very reactive constituent of surface and subsurface environments and, as a result, impacts regional ecological phenomena. |
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