Syntrophic interspecies electron transfer drives carbon fixation and growth by <i>Rhodopseudomonas palustris</i> under dark, anoxic conditions.
basic_science · Level V
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- Record sourced from PubMed, PMID 34215588.
- Also identified by DOI 10.1126/sciadv.abh1852 and PMC identifier 11057707.
- Licence recorded as CC BY-NC.
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Abstract
In natural anoxic environments, anoxygenic photosynthetic bacteria fix CO<sub>2</sub> by photoheterotrophy, photoautotrophy, or syntrophic anaerobic photosynthesis. Here, we describe electroautotrophy, a previously unidentified dark CO<sub>2</sub> fixation mode enabled by the electrosyntrophic interaction between <i>Geobacter metallireducens</i> and <i>Rhodopseudomonas palustris.</i> After an electrosyntrophic coculture is formed, electrons are transferred either directly or indirectly (via electron shuttles) from <i>G. metallireducens</i> to <i>R. palustris,</i> thereby providing reducing power and energy for the dark CO<sub>2</sub> fixation. Transcriptomic analyses demonstrated the high expression of genes encoding for the extracellular electron transfer pathway in <i>G. metallireducens</i> and the Calvin-Benson-Bassham carbon fixation cycle in <i>R. palustris</i> Given that sediments constitute one of the most ubiquitous and abundant niches on Earth and that, at depth, most of the sedimentary niche is both anoxic and dark, dark carbon fixation provides a metabolic window for the survival of anoxygenic phototrophs, as well as an as-yet unappreciated contribution to the global carbon cycle.