BRIGE: Proposal to Study Self-Assembling Siderophore Vesicles

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."PI: Richards, AbigailProposal Number: 0927109Intellectual Merit: Surfactant molecules have the ability to alter interfacial characteristics and phenomena. This proposal will fund an investigation into the conditions affecting both micelle and vesicle formation by biosurfactant siderophores, the sodachelins, as well as determine the stability of these vesicles in a variety of conditions, once formed. The sodachelins are a group of novel amphiphilic siderophores (iron chelating molecules) secreted by a soda lake bacterial isolate. Until recently, most research involving siderophore production has focused on pathogenic microbes or those inhabiting non-extreme environments. Over the past decade, studies focused on marine microbes resulted in the discovery of several new siderophores with novel traits such as UV-induced iron reduction, micelle formation and ironinduced vesicle formation. An in depth study of the sodachelins will further elucidate factors governing micelle to vesicle transitions. The sodachelin siderophores consist of a peptidic, iron-chelating head group appended to a series of different fatty acid tails of various carbon length (C10 to C14) and level of unsaturation. The sodachelins are very similar in structure to other known amphiphilic siderophores, produced by marine bacteria, which are reported to form micelles that can self-assemble into vesicles, forming small nano-spheres on the order of 200nm. This self-assembly is triggered by the addition of excess iron, beyond what is already coordinated by the iron chelating head group, generating a spherical structure with iron rich surfaces. Because of structural similarities of the sodachelins to these molecules, it is hypothesized that the sodachelins will also form micelles and vesicles in a similar mechanism. Proposed work involves and analysis of the conditions favoring vesicle formation by the sodachelins, as well as mechanisms that may facilitate a controlled disaggregation of the vesicles. Two methods of disaggregation will be studied. Because the sodachelins were previously found to undergo a UV-induced photolysis it is postulated that UV exposure could trigger a controlled disassembly of the vesicles. A second possible mechanism of vesicle disassembly to be tested in this research is the removal of the iron coordinated on the outer vesicle surface by a strong metal chelator. The iron coordinated by the outer shell is thought to be coordinated with lower affinity and may be easily removed upon the introduction of another metal chelator, inducing the disaggregation of the vesicle structure. The study of the controlled formation and disruption of the vesicles may lead to future advances in biocide applications and drug delivery systems.Broader Impacts: The work proposed will lay the foundation for future investigations by the PI in biocide delivery applications and investigations of vesicle stability under shear stress in flow conditions. While this is primarily a research proposal, a second, but more important deliverable is to broaden the participation of underrepresented groups in science and engineering. The PI, herself a young investigator in her first tenure track appointment has budgeted for both graduate and undergraduate student support. A female American Indian undergraduate student is currently working for the PI as an undergraduate research assistant and will be funded in the future on this project. The PI and this undergraduate will visit Montana Tribal colleges to present experiences and opportunities available in science and engineering careers. A Hispanic American doctoral student has also been identified to conduct much of the research outlined within and will serve to increase the number of minorities serving as role models at the doctoral level. Also provided in this proposal are opportunities are for local high school students to work with the PI on a portion of this proposed research during the summer. Finally, the PI will actively disseminate advancements made through this work at scientific meetings, peer reviewed journal articles and the Soap Lake Conservancy?s Science Symposia which is a bi-annual presentation of research involving Soap Lake delivered to the lay, rural community-members living near the lake.