Non‐Respiratory Extracellular Electron Transfer Competes with Nitrogenase for Electrons in Rhodopseudomonas Palustris
Xuewen Liu, Panqing Qi, Wei Fan, Wuyang Liu +3
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92% confidenceThis study investigates the interaction between photosynthetic nitrogen fixation (BNF) and outward extracellular electron transfer (EET) in Rhodopseudomonas palustris TIE-1 using a photosynthetic bioelectrochemical system. The key finding is that outward EET functions as a redox-balancing mechanism rather than an energy-generating respiratory pathway, and critically, it competes with nitrogenase for electrons, thereby suppressing BNF. Lumichrome serves as the primary indirect electron shuttle while cytochromes mediate direct electron transfer, with the pio operon participating in EET.
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Abstract
Biological nitrogen fixation (BNF) is a pivotal process that reduces nitrogen to ammonium within the nitrogen cycle. Extracellular electron transfer (EET) between diazotrophs and the extracellular environment influences the occurrence and efficiency of BNF. Although extracellular electron acceptors can function as a component of the electron transport chain, providing energy for chemotrophic nitrogen fixation via extracellular respiration, the function and mechanism of outward EET in photosynthetic diazotrophs remain unclear. Here, using Rhodopseudomonas palustris TIE-1, a photosynthetic bioelectrochemical nitrogen fixation system is established for simultaneous nitrogen fixation and current generation, to dissect the complex interaction between these two processes. Outward EET functions are found to maintain redox balance, rather than serving as an extracellular respiration pathway. It significantly suppresses BNF by competing with nitrogenase for electrons. Lumichrome serves as the primary electron shuttle for indirect electron transfer, while cytochromes play an important role in direct electron transfer. Notably, the pio operon participates in outward EET. This study reveals the interaction mechanism between photosynthetic BNF and outward EET, providing new insight into the regulatory mechanisms of nitrogen fixation in anoxygenic phototrophs across diverse environmental conditions.
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Identifiers
- PubMed
- 40367360
- Journal
- Advanced Science
- Year
- 2025