show Abstracthide AbstractIodine is an essential element needed in trace amounts by a variety of living organisms that acquire it through their diet in most cases. Iodine is made available through biogeochemical cycling. Most of what we know about iodine biogeochemical cycling is based on studies of marine systems and the atmosphere. Although oceans are the predominant global source of iodine, there remains an unaccounted for contributor. This research will help explain how bacteria in soil, sediments, and groundwater also participate in global iodine cycling by studying genes potentially associated with iodine transformation. This project uses functional and comparative genomics approaches to identify bacterial genes that contribute to iodine biogeochemical cycling and iodine speciation at the Hanford Site (WA, USA), where radioisotope iodine-129 is a contaminant.