The electron transport chain of Shewanella oneidensis MR-1 can operate bidirectionally to enable microbial electrosynthesis
The electron transport chain of Shewanella oneidensis MR-1 can operate bidirectionally to enable microbial electrosynthesis
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DOI：
10.1128/aem.01387-23
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发表时间：
2023-12-20
影响因子：
4.4
通讯作者：
Buan，Nicole R.
中科院分区：
文献类型：
--
作者：
Ford，Kathryne C.;Teravest，Michaela A.;Buan，Nicole R.
细胞外电子转移是细菌细胞可以与位于细胞外的氧化还原活性物质交换电子的过程。在Shewanella oneidensis中，该过程本身用于使用细胞外电子受体（例如Fe（III）或阳极）来促进呼吸。先前，已证明该过程可用于驱动在性表达丁二醇脱氢酶（BDH）的洋葱链球菌中的2，3-丁二醇（2，3-BD 0）的微生物电合成（MES）。从阴极进入电池的电子用于产生NADH，其进而用于经由BDH将乙偶姻还原为2，3-BD 0。然而，通过从阴极吸收电子产生NADH在能量上是不利的，因此NADH脱氢酶将反应与质子动力耦合。因此，我们需要保持跨膜的质子梯度以维持NADH的产生。这项工作探索通过双向电子转移来完成这项任务，其中阴极提供的电子通过氧化酶同时进行NADH形成和氧气（O2）还原。我们发现，氧化酶使用微量溶解氧在微氧生物电化学系统（BES），和跨膜的质子易位O2还原过程中支持2，3-BDO的产生。有趣的是，这一过程受到该系统中高水平溶解氧的抑制。在曝气BES中，O2分子与强还原剂（阴极）反应形成活性氧，导致细胞死亡。重要信息微生物电合成（MES）越来越多地用于生产特种化学品，如生物燃料，生物塑料和癌症治疗剂。为了使这些系统在工业规模上可行，重要的是要了解细菌的能量需求，以减少不必要的成本。这项工作证明了由阴极驱动的工业相关化学品的持续生产。此外，它通过消除对光养能量的任何要求来优化先前公布的系统，从而消除提供光源的额外成本。我们还展示了氧气侵入生物电化学系统的严重影响，为未来在厌氧环境中工作的研究人员提供了见解。这些研究为电合成的热力学和生物电化学系统设计的重要性提供了见解。
Extracellular electron transfer is a process by which bacterial cells can exchange electrons with a redox-active material located outside of the cell. InShewanella oneidensis, this process is natively used to facilitate respiration using extracellular electron acceptors such as Fe(III) or an anode. Previously, it was demonstrated that this process can be used to drive the microbial electrosynthesis (MES) of 2,3-butanediol (2,3-BDO) inS. oneidensisexogenously expressing butanediol dehydrogenase (BDH). Electrons taken into the cell from a cathode are used to generate NADH, which in turn is used to reduce acetoin to 2,3-BDO via BDH. However, generating NADH via electron uptake from a cathode is energetically unfavorable, so NADH dehydrogenases couple the reaction to proton motive force. We therefore need to maintain the proton gradient across the membrane to sustain NADH production. This work explores accomplishing this task by bidirectional electron transfer, where electrons provided by the cathode go to both NADH formation and oxygen (O2) reduction by oxidases. We show that oxidases use trace dissolved oxygen in a microaerobic bioelectrical chemical system (BES), and the translocation of protons across the membrane during O2reduction supports 2,3-BDO generation. Interestingly, this process is inhibited by high levels of dissolved oxygen in this system. In an aerated BES, O2molecules react with the strong reductant (cathode) to form reactive oxygen species, resulting in cell death.IMPORTANCEMicrobial electrosynthesis (MES) is increasingly employed for the generation of specialty chemicals, such as biofuels, bioplastics, and cancer therapeutics. For these systems to be viable for industrial scale-up, it is important to understand the energetic requirements of the bacteria to mitigate unnecessary costs. This work demonstrates sustained production of an industrially relevant chemical driven by a cathode. Additionally, it optimizes a previously published system by removing any requirement for phototrophic energy, thereby removing the additional cost of providing a light source. We also demonstrate the severe impact of oxygen intrusion into bioelectrochemical systems, offering insight to future researchers aiming to work in an anaerobic environment. These studies provide insight into both the thermodynamics of electrosynthesis and the importance of the bioelectrochemical systems’ design.