Collaborative research: Functional genomic investigations of iron and carbon cycle coupling in select keystone marine Bacteria heterotrophs

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As a scarce but essential micronutrient for microbial growth in the marine environment, iron plays a critical role in supporting marine primary productivity and is tightly coupled to the cycling of carbon and other nutrients. Significant progress in recent years has been made in understanding the distribution of iron in the oceans and the impact of iron limitation on phytoplankton. Many questions remain, however, about the extensive biogeochemical linkages that exist between iron and carbon in marine systems. Bacteria represent a crucial and understudied node in this network. The proposed work will explore linkages between the carbon and iron cycles in marine systems in the context of the heterotrophic bacteria that are the primary drivers of the turnover of organic matter in the oceans. The project will support a postdoctoral researcher, as well as undergraduate interns. UCSD Bioengineering Senior Design Thesis students will be entrained to develop projects related to synthetic biology. The team will also host a 3-day workshop, in collaboration with Scripps Educational Alliances and the San Diego County Office of Education (SDCOE), to develop Next Generation Science Standards and CA Science Framework-aligned activities and resources for high school teachers in California. Educational activities will be based on “phenomena” associated with the proposed research, and after appropriate testing and refinement by local science teachers, will be broadly disseminated by the SDCOE. A functional genomics approach will be employed, using model organisms that have been shown to represent a spectrum in terms of their carbon substrate utilization and lifestyle strategies. Alteromonas spp., with numerous TonB-dependent outer membrane receptors and hydrolytic enzyme capabilities, are known for their ability to degrade and assimilate complex (i.e. high molecular weight) marine dissolved organic matter. In contrast, well-studied Roseobacters, with large numbers of inner-membrane transporters, specialize in the transport of low- molecular-weight organic matter. This project asks fundamental questions about how iron substrate utilization and iron-related physiology contribute to the known niche specificity of these organisms and impact carbon processing. These questions will be addressed through a combination of transcriptomic, mutagenic and experimental approaches with model strains. This work aims to advance the field so that conceptual models of microbial iron recycling can be integrated with current conceptual models of organic carbon recycling by marine bacteria. In addition, the functional genomics approach proposed here will identify and validate targets for meta-omic, meta- proteomic, and bioinformatic investigations of the links between iron and carbon cycling in the ocean, enabling better interrogation of existing and planned large-scale ocean datasets such as Tara Oceans, GEOTRACES, and BioGeoSCAPES.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.