CAREER: Rusting the Earth: the mechanisms and mineralogy of microbial Fe oxidation

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Microbes are numerous, widespread, and metabolically-versatile organisms, impacting virtually every environment on Earth?s surface. Fe-oxidizing microorganisms (FeOM) have likely been oxidizing, or ?rusting,? the Earth for billions of years. In near-neutral pH environments, FeOM form iron oxyhydroxides, which adsorb metals, organics, and other nutrients, affecting element bioavailability, C cycling, and soil and water quality. Microbial Fe oxidation is predicted to accelerate Fe oxidation rates in low oxygen, Fe(II)-rich environments found in circumneutral aquifers and soils, where abiotic oxidation rates are slow. However, few neutrophilic FeOM species have been unambiguously shown to oxidize Fe; therefore we know little about the diversity, genetics, and biochemistry of FeOM that function at neutral pH. My overall aim is to develop an integrated microbiological, biochemical, mineralogical and geochemical understanding of Fe microbial oxidation, in order to accurately describe modern and ancient Fe cycling on Earth. We first need to develop methods to recognize and quantify circumneutral microbial Fe oxidation and effects, so this project has the following research objectives: (1) Isolate and characterize novel FeOM from groundwater and thus expand the currently limited knowledge of FeOM diversity; (2) Discover candidates for key genes/proteins involved in Fe oxidation, to gain insight into bio(geo)chemical mechanisms and to give us the abilities to assay Fe-oxidation and recognize the genetic capability in (meta)genomes; (3) Characterize C metabolism and related genes in isolates, to understand how microbial Fe oxidizers can influence C cycling. This work will involve a combination of culturing and physiological characterization, differential gene/protein expression, qPCR, as well as sequencing and analysis of isolate genomes and environmental 16S rRNA and other genes. We will work in conjunction with the NSF Christina River Basin Critical Zone Observatory (CRB-CZO) in DE and PA, using CRB-CZO sites as a source of novel FeOM and as a testing ground for our new methods for detecting FeOM presence and activity. The research themes will be integrated into educational activities that train students to think creatively and work across disciplines. Creativity and interdisciplinary scientific thought is vital to the innovation and problem-solving needed to advance our society and address environmental issues. Such skills take practice, so the main educational objectives are to (1) develop an inquiry-based undergraduate geomicrobiology class and (2) create a curriculum for a ?Microbes in the Wild!? science module for under-represented female middle school students in the Serviam Academy. I will also train a postdoctoral researcher and a PhD student over the course of the project. The research will be incorporated into continuing outreach programs, including school presentations, teacher workshops, the college?s annual Coast Day, Science Café, and other opportunities organized by the DE Sea Grant office.