Since the discovery of iodine in 1811 by Barnard Courtois, researchers have learned a lot about its biological significance to humans and other organisms. Unlike other elements, iodine exists almost exclusively in marine environments. Across the world's oceans, nearly 95% of iodine persists as iodate (IO3-) and must be reduced to iodide (I-) to become bioavailable. Once reduced, iodine bioaccumulates in kelp to produce several volatile iodine species (VOIs). These VOIs, in turn, form aerosols at the marine boundary layer and contribute to the destruction of tropospheric ozone (a greenhouse gas). Early research into the iodine cycle often suggested a biological component but never thoroughly explained the impact of microorganisms on iodine mobilization.
Over the past 30 years, emerging evidence demonstrates that microorganisms are active participants in the iodine cycle. We have identified several new bacteria that possess a dedicated pathway for reducing IO3- to I- and generating energy for growth in the process by using a protein complex called an iodate reductase (Idr). We have also identified unique niches in which these bacteria exist, which can help explain how these bacteria impact their local environments. We remain focused on gaining a mechanistic understanding of the processes involved in this metabolism and searching for new places where it may exist. To achieve this, we combine approaches from microbial physiology, genetics, genomics, enzymology, and microbial ecology. Ultimately, we aim to understand what evolutionary pressures brought this iodate respiration into existence, how iodate respiration impacts the global iodine cycle, and how this changes our foundational understanding of microbial metabolisms and electrochemistry.
Published Literature:
Reyes-Umana, V., Henning, Z., Lee, K. et al. Genetic and phylogenetic analysis of dissimilatory iodate-reducing bacteria identifies potential niches across the world’s oceans. ISME J(2021). https://doi.org/10.1038/s41396-021-01034-5