Dr. Parenteau will speak about her research into the early evolution of oxygenic photosynthesis in the context of Archean ferruginous oceans, and how this might relate to ancient banded iron formations. Banded Iron Formations (BIFs) are widespread Precambrian sedimentary deposits that accumulated in deep ocean basins with inputs of reduced iron (Fe(II)) and silica from deep ocean hydrothermal vents.
There is scientific debate as to whether abiotic or biotic mechanisms were responsible for the oxidation of Fe(II) and the deposition of BIFs. Biotic mechanisms could include (1) indirect oxidation via the photosynthetic production of oxygen by cyanobacteria, (2) direct oxidation by anoxygenic phototrophs, and (3) direct oxidation by chemolithotrophs. Dr. Parenteau's work will also examine another potential mechanism: direct oxidation by ancestral cyanobacteria that can use Fe(II) as an electron donor for photosynthesis. Dr. Parenteau has been searching for modern descendants of these organisms in the phototrophic mats at Chocolate Pots, a high Fe(II) hot spring in Yellowstone National Park.