Distinguished Speaker Dr. Jennifer Macalady Assesses Proterozoic Oxygen Levels This Week
This week the Distinguished Speaker Series presents Dr. Jennifer Macalady, Associate Professor in the Department of Geosciences at PennState University.
"Light-Harvesting Bacteria Stabilized Low-Oxygen Conditions in the Proterozoic"
Understanding the protracted delay in the oxygenation of the global ocean-atmosphere system during the Proterozoic remains a major challenge in earth science.Anoxic ocean conditions would have been eroded by the advent of oxygenic photosynthesis and geological trends such as the stabilization of the continents and increased subaerial vs. submarine volcanism.Feedbacks that would stabilize low-oxygen conditions in the Proterozoic for 2 billion years after the Great Oxidation Event have proven more difficult to identify, highlighting an important gap in our understanding of ancient biogeochemical cycling. Significant contributions to primary production by anoxygenic phototrophs, including metabolically versatile cyanobacteria, would have generated organic matter via oxidation of reduced S,with no O2 production. The resulting positive feedback would stall the accumulation of O2 in the oceans and atmosphere. Biological mechanisms that govern interactions among light-harvesting bacteria are yielding new insights about how it might work. We captured and domesticated a filamentous, metabolically versatile cyanobacterium (Leptolyngbya sp. strain “hensonii") from a benthic pinnacle mat that blooms in a sulfidic spring. The genome of the isolate encodes all of the enzymatic necessary for both oxygenic and anoxygenic photosynthesis. In situ, the pinnacle mats carry out anoxygenic photosynthesis during all daylight hours, and oxygenic photosynthesis for only a few hours per day while sulfide is completely depleted in the mats. The implications of this behavior for Proterozoic oxygen levels will be revealed, along with other dark cyanobacterial secrets.
Join us for this assessment of Proterozoic Oxygen Levels on Friday, September 7, 2018 at 12:30 PM in Room 204, Natural Science Building on the East Lansing Campus.