Photosynthesis is a key process for primary productivity in nature. The electron donor range for photosynthesis is limited to water for organisms such as plants, algae and cyanobacteria. These organisms split water to produce oxygen as a byproduct of photosynthesis. Hence, they are called oxygenic phototrophs. In contrast to oxygenic phototrophs, anoxygenic phototrophs can use a much wider range of electron donors. Till recently, this was limited to soluble electron donors such as hydrogen, sulfide and thiosulfate to name a few. My laboratory recognized that anoxygenic phototrophs can also use insoluble electron donors such as metal oxides and their proxies as electron donors as well. In essence, we see that anoxygenic phototrophs can use electricity as an electron donor. We refer to this metabolism as photoelectroautotrophy, and have recently shown that this process is connected to carbon dioxide fixation via the Calvin-Benson-Bassham cycle. Thus, this process results in primary productivity. We have also shown that electrons enter the photosynthetic reaction center via a two-protein outer membrane complex called PioAB, where PioA encodes a decaheme cytochrome c protein and PioB is an outer membrane porin. The first examples that we studied for photoelectroautotrophy were noted in freshwater organisms. To determine if this process also occurs in marine ecosystems, we isolated 20 microbes that can all perform photoelectroautotrophy. We have characterized various aspects of this ability in these organisms, and note that the underlying mechanism of electron transfer is fundamentally different in marine phototrophs. Importantly, photoelectroautotrophy is now noted to be important in both freshwater and marine ecosystems.

Exploring the electric side of photosynthesis and its influence of biogeochemical cycles

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.