Expanding the Bio in Biogeochemistry: Cyanobacteria and the Great Oxygenation Event.

• Applicant: Dr. Michelle Gehringer
• Subject Area: Mineralogy, Petrology and Geochemistry ; Palaeontology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 276888694

The Great Oxygenation Event (GOE), whereby the early Earths atmosphere was oxygenated, was thought to be a single step event occurring about 2.3 Ga. Recent evidence suggests however that niches of raised oxygen levels existed prior to this, approximately 3 Ga. Cyanobacteria, by virtue of oxidative photosynthesis, are considered a key contributor to atmospheric oxygenation. Life on early Earth is evidenced with scant stromatolitic formations and microbial mats from sedimentary rocks dating from the Archean. Phylogenetic analysis of modern-day Cyanobacteria, using many genes and molecular clock algorithms, have identified ancient lineages of Cyanobacteria that originated prior to and after the GOE. Whether the signature molecules and profiles currently utilised in biogeochemistry and geomicrobiology could actually be generated by ancient Cyanobacteria under the conditions thought to have existed during the Archean, has not been determined. Our project will address this research gap by assessing the growth responses of modern day descendants of ancient cyanobacterial lineages under reduced O2 levels, in both marine and freshwater species and to correlate the obtained mineralogic data, specifically that pertaining to carbonate and iron cycling, with the existing biogeochemical records. We thereby aim to integrate the existing biogeochemical record and cyanobacterial phylogenetic history with ecophysiological studies and mineralogic analysis of modern-day analogue micro-organisms under conditions thought to have existed towards the end of the Archean, answering the question: How did Cyanobacteria affect the oxygenation of the early Earths atmosphere?

• DFG Programme: Priority Programmes
• Subproject of: SPP 1833: Building a Habitable Earth