Eberwein Marie, Hellmold Nadine, Frank Ronny, Deobald Darja, Adrian Lorenz
Department Molecular Environmental Biotechnology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
Centre for Biotechnology and Biomedicine, Biochemical Cell Technology, Leipzig University, Leipzig, Germany.
Front Microbiol. 2024 Oct 23;15:1457014. doi: 10.3389/fmicb.2024.1457014. eCollection 2024.
Microorganisms capable of direct or mediated extracellular electron transfer (EET) have garnered significant attention for their various biotechnological applications, such as bioremediation, metal recovery, wastewater treatment, energy generation in microbial fuel cells, and microbial or enzymatic electrosynthesis. One microorganism of particular interest is the organohalide-respiring bacterium strain CBDB1, known for its ability to reductively dehalogenate toxic and persistent halogenated organic compounds through organohalide respiration (OHR), using halogenated organics as terminal electron acceptors. A membrane-bound OHR protein complex couples electron transfer to proton translocation across the membrane, generating a proton motive force, which enables metabolism and proliferation. In this study we show that the halogenated compounds can be replaced with redox mediators that can putatively shuttle electrons between the OHR complex and the anode, coupling cells to an electrode mediated EET. We identified cobalt-containing metal complexes, referred to as cobalt chelates, as promising mediators using a photometric high throughput methyl viologen-based enzyme activity assay. Through various biochemical approaches, we show that cobalt chelates are specifically reduced by CBDB1 cells, putatively by the reductive dehalogenase subunit (RdhA) of the OHR complex. Using cyclic voltammetry, we also demonstrate that cobalt chelates exchange electrons with a gold electrode, making them promising candidates for bioelectrochemical cultivation. Furthermore, using the AlphaFold 2-calculated RdhA structure and molecular docking, we found that one of the identified cobalt chelates exhibits favorable binding to RdhA, with a binding energy of approximately -28 kJ mol. Taken together, our results indicate that bioelectrochemical cultivation of with cobalt chelates as anode mediators, instead of toxic halogenated compounds, is feasible, which opens new perspectives for bioremediation and other biotechnological applications of strain CBDB1.
能够进行直接或介导的细胞外电子转移（EET）的微生物因其在各种生物技术应用中的潜力而备受关注，例如生物修复、金属回收、废水处理、微生物燃料电池中的能量产生以及微生物或酶促电合成。一种特别受关注的微生物是有机卤化物呼吸细菌菌株CBDB1，它以能够通过有机卤化物呼吸（OHR）将有毒且持久的卤代有机化合物进行还原脱卤而闻名，利用卤代有机物作为末端电子受体。一种膜结合的OHR蛋白复合物将电子转移与跨膜质子转运偶联，产生质子动力，从而实现代谢和增殖。在本研究中，我们表明卤代化合物可以被氧化还原介质替代，这些介质可能在OHR复合物和阳极之间穿梭电子，将细胞与电极介导的EET偶联起来。我们使用基于甲基紫精的光度高通量酶活性测定法，确定含钴金属配合物（称为钴螯合物）为有前景的介质。通过各种生化方法，我们表明钴螯合物被CBDB1细胞特异性还原，推测是由OHR复合物的还原脱卤酶亚基（RdhA）进行的。使用循环伏安法，我们还证明钴螯合物与金电极交换电子，使其成为生物电化学培养的有前景候选物。此外，利用AlphaFold 2计算的RdhA结构和分子对接，我们发现一种鉴定出的钴螯合物与RdhA表现出良好的结合，结合能约为-28 kJ/mol。综上所述，我们的结果表明，以钴螯合物作为阳极介质而非有毒卤代化合物对菌株CBDB1进行生物电化学培养是可行的，这为菌株CBDB1的生物修复和其他生物技术应用开辟了新的前景。
