SCOL Project: Signatures of biological and environmental co-evolution on the early Earth
Sedimentary rocks from shallow water environments store a 3.5 billion year long record of interactions between early life and its habitats. However, it is currently unclear what chemicals supported ecosystems in these habitats, how microbes moved and colonized sediments, whether microbes helped form rocks and precipitate rock-forming minerals and when the early light-harvesting microbes became able to evolve oxygen. Answers to these questions, inferred from the shapes of rocks and traces of chemical signals, require better constraints on signals that can be produced and preserved in the presence of microbial communities that do not evolve oxygen. The proposed work will address this by establishing communities of light-harvesting microbes that colonize sediments and promote the precipitation of rock-forming minerals under a range of chemical conditions relevant for the early Earth and other young planets. The shapes of microbial structures and sedimentary rocks will be investigated under a range of light conditions, sediment grain sizes and flow velocities, and as a function of microbial production of gases such as methane. Experiments with microbial cultures will explore the roles of iron, sulfur and organic compounds as drivers of light-harvesting processes and mineral formation in shallow water sediments. A major aim of these experiments is to identify chemical conditions and microbial communities that promote the precipitation of rock-forming minerals and facilitate the preservation of biologically-produced shapes and chemical signals. The shapes and chemical properties of microbially-produced structures and minerals will be investigated by analytical techniques at a range of scales, from visible to those smaller than a microbial cell. Insights from the laboratory will be used to reconstruct microbial processes from geologic samples.
Tanja Bosak was born in Croatia and graduated from the Zagreb University with a degree in Geophysics. After a summer of research at JPL and a short stint as a meteorologist at the Zagreb Airport, she moved to the California Institute of Technology in Pasadena, where she studied signatures of microbial processes in ancient sedimentary rocks and earned a Ph.D. in Geobiology. She spent two years at Harvard as a Microbial Initiative Postdoctoral Fellow, joined the Department of Earth, Atmospheric and Planetary Sciences at MIT in 2007 and is now an associate professor of Geobiology. Tanja’s work integrates microbiology, sedimentology and stable isotope geochemistry into experimental geobiology to ask how microbes shape sedimentary rocks, how organisms fossilize and how microbial metabolisms leave biogeochemical patterns in sediments. Her lab uses this approach to explore modern biogeochemical and sedimentological processes and interpret the record of life on the Early Earth. For this work, and her work with graduate students and undergraduates, Bosak received the Subaru Outstanding Woman in Science award by the Geological Society of America (2007), the Macelwane Medal from the American Geophysical Union (2011), the Edgerton Award for young faculty at MIT (2012) and the Undergraduate Research Opportunities for Undergraduates Mentor of the Year award by MIT (2012). Bosak is a fellow of the American Geophysical Union (2011) and one of the subject editors of Geobiology.