Collaborative Research: Using Single-Molecule Force and Fluorescence Microscopy to Elucidate the Molecular Mechanism of Bioinspired Magnetite Synthesis in Magnetotactic Bacteria

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Microorganisms are the oldest living inhabitants of planet Earth, spanning some 3.5 billion years, and their importance in shaping the Earth?s soils, oceans, and atmosphere has long been accepted. The biosynthesis of magnetite (Fe3O4) by magnetotactic bacteria is an interesting example that has generated a great deal of interest because of its importance in applications such as catalysis, electronics, nanotechnology, and biomedical sciences, its philosophical implications concerning the origin and evolution of life on Earth, and its potential to participate in the biogeochemical cycling of iron, nitrogen, sulfur, and carbon in natural environments. 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 and global scale climatic and ecological phenomena. In addition, despite its ubiquity and because of it reactivity, iron is often a limiting factor for growth of organisms, for example, in some parts of the world?s oceans. From the point of view of mineralization, biological control over nucleation and directed growth of nanominerals is an elegant example of self-organization in complex molecular systems. Despite the discovery of magnetotactic bacteria over 30 years ago, the mechanism for Fe3O4 biomineralization in these microorganisms remains unknown. The objective of this research is to use single-molecule techniques of atomic force (single-molecule antibody recognition force microscopy) and fluorescence microscopy/spectroscopy (time-resolved fluorescence anisotropy and fluorescence resonance energy transfer) to determine the molecular mechanism for the biomineralization of nanomagnetite crystals in magnetotactic bacteria. Investigators will identify the function(s) of the individual 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 Fe3O4 biomineralization. The broader impacts resulting from the proposed activity ? Understanding the molecular mechanism by which bacteria direct the synthesis of Fe3O4 nanoparticles represents an important paradigm for bioinspired materials synthesis that would provide enormous insight into the strategies of controlled crystal synthesis used by other organisms, including multi-cellular organisms. By understanding the biomineralization process of Fe3O4 in magnetotactic bacteria, we might learn how to determine whether Fe3O4 grains in the environment are biogenic in origin, which, in turn, might provide evidence of reliability for the use of Fe3O4 crystals found in the environment to be used as biomarkers for past life on Earth. Furthermore, because technological progress often relies on a detailed understanding of the material properties of single crystals, composites, interfaces, and nanocrystals, and because the mineralization process in microorganisms is inherently controlled by nanoscale structures (e.g., proteins), this knowledge will become the basis for bio-controlled approaches to synthesize tailor-made inorganic nanostructures for applications across a diverse span of technologies. Finally, investigators believe that the novel imaging techniques developed as a result of this project will emerge as powerful tools that can be used for studies in other geobiological or biological systems. The proposed research will support a new collaboration between the two PIs and two Ph.D. graduate students (one student from each laboratory) who will play an integral role in this research and be encouraged to present their findings at international and national conferences and local seminars at each university. One PI is an early-career faculty member who has helped pioneer efforts to develop imaging techniques to study geobiological processes on a molecular level and the second PI is a senior faculty member who is a world-renowned authority in magnetite biomineralization and has authored over 150 publications in this field. This proposal will also fund 1 female PhD student who works in the Lead- PI?s laboratory. The results of this research will be integrated into the undergraduate and graduate courses currently taught and being developed by the PIs. Furthermore, this proposal will support efforts to educate elementary, middle-, and high school age students about the burgeoning yet often overlooked fields of nanogeoscience and biogeochemistry through hands-on demonstrations and presentations. These efforts will be geared to encourage pre-college students to pursue careers in biogeochemistry and/or become responsible stewardesses of the environment.