The role of iron (Fe) as a limiting agent of biological productivity in marine systems has been studied extensively. Marine prokaryotic organisms are known to maintain the ability to produce siderophore (or at least siderophore-like compounds) in response to Fe-limiting growth conditions. While research analytical techniques can quantify total Fe at incredibly small concentrations and provide information on Fe speciation, we remain without indicators of the biological availability of this Fe to natural communities. To understand the role that Fe plays in global marine productivity, tools/techniques for quantifying truly bioavailable iron are needed. Since organisms in aquatic systems can determine their own Fe status, a tool based on the Fe sensing system of a marine organism would be the best. The investigators have developed a genetically engineered microorganism (GEM) with a luminescent reporter that directly responds to Fe bioavailability using the native ferric-uptake-regulator (Fur) protein of a marine bacterium. The researchers will now attempt integration of the reporter into ten other strains of marine bacteria. Laboratory experiments will establish the relationship between Fe bioavailability and light production. Field testing of the GEMs as Fe bioavailability reporters will be conducted on cruises of opportunity in the Sargasso Sea, Lake Erie, and the Peru upwelling region.
SGER: Development of a Reporter System Regulated by the Biological Availability of Fe in Saltwater