Anoxygenic photosynthesis and the delayed oxygenation of Earth's atmosphere.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31289261.
- Also identified by DOI 10.1038/s41467-019-10872-z and PMC identifier 6616575.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The emergence of oxygenic photosynthesis created a new niche with dramatic potential to transform energy flow through Earth's biosphere. However, more primitive forms of photosynthesis that fix CO<sub>2</sub> into biomass using electrons from reduced species like Fe(II) and H<sub>2</sub> instead of water would have competed with Earth's early oxygenic biosphere for essential nutrients. Here, we combine experimental microbiology, genomic analyses, and Earth system modeling to demonstrate that competition for light and nutrients in the surface ocean between oxygenic phototrophs and Fe(II)-oxidizing, anoxygenic photosynthesizers (photoferrotrophs) translates into diminished global photosynthetic O<sub>2</sub> release when the ocean interior is Fe(II)-rich. These results provide a simple ecophysiological mechanism for inhibiting atmospheric oxygenation during Earth's early history. We also find a novel positive feedback within the coupled C-P-O-Fe cycles that can lead to runaway planetary oxygenation as rising atmospheric pO<sub>2</sub> sweeps the deep ocean of the ferrous iron substrate for photoferrotrophy.