This project is awarded under the Minority Postdoctoral Research Fellowships and Supporting Activities Program for 2006. Recently, biologists and geologists have acknowledged the omnipresence and importance of natural nanoparticles, which are crystalline materials with dimensions less than or equal to 100 nm. These nanoparticles occur often as mineral colloids (particles suspended in solution). While physicists and chemists have found synthetic nanoparticles to display novel properties as a function of size, very little is known about natural nanoparticles. To understand their behavior in natural systems (e.g. soils, groundwater, surface water, really all ecosystems) it is critical to know how native living organisms interact with them. Currently, we know very little about nanoparticle-organism interactions, especially in any environmentally-relevant context. Under the mentorship of Dr. Michael Hochella at Virginia Tech University, I will address this current void in our knowledge by studying the interactions of a common type of iron-reducing soil bacterium, Shewanella oneidensis, with iron(III) oxide nanoparticles. Under anaerobic conditions, it is well known that S. oneidensis can respire using iron(III) oxides by reducing the iron from the ferric to ferrous states, dissolving these otherwise highly insoluble minerals in the process. I will focus on the bioreduction rate of iron(III) oxide nanoparticles as a function of particle size. As mineral colloids are also known to carry toxic metals, I will also study the interactions of S. oneidensis with cobalt- and lead-contaminated iron oxide nanoparticles. Study of these interactions will have broad implications, not only for fundamental geobiological processes, but also for pollutant transport, the global carbon cycle, and the potential environmental impacts of nanotechnology. My scientific and professional goals for this fellowship tenure are as follows. I wish to successfully transition from my current field (materials physical chemistry/nanoscience) to the field of biogeochemistry. To do this I plan, during my tenure, to gain expertise in environmental microbiology and geochemistry. I will also continue to apply my nanoscience background to problems relevant to biogeochemistry. Professionally, I hope to establish myself in the biogeochemistry community by publishing high-level peerreviewed work, as well as becoming acquainted with other biogeochemists via scientific conferences and other networks. My ultimate goal is to become a research scientist, either as a professor at a university, or a staff scientist at a national laboratory.
