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Geobacter sulfurreducens inner membrane cytochrome CbcBA controls electron transfer and growth yield near the energetic limit of respiration
Molecular Microbiology ( IF 3.6 ) Pub Date : 2021-08-23 , DOI: 10.1111/mmi.14801
Komal Joshi 1, 2 , Chi Ho Chan 1 , Daniel R Bond 1, 3
Affiliation  

Geobacter sulfurreducens utilizes extracellular electron acceptors such as Mn(IV), Fe(III), syntrophic partners, and electrodes that vary from +0.4 to −0.3 V versus standard hydrogen electrode (SHE), representing a potential energy span that should require a highly branched electron transfer chain. Here we describe CbcBA, a bc-type cytochrome essential near the thermodynamic limit of respiration when acetate is the electron donor. Mutants-lacking cbcBA ceased Fe(III) reduction at −0.21 V versus SHE, could not transfer electrons to electrodes between −0.21 and −0.28 V, and could not reduce the final 10%–35% of Fe(III) minerals. As redox potential decreased during Fe(III) reduction, cbcBA was induced with the aid of the regulator BccR to become one of the most highly expressed genes in G. sulfurreducens. Growth yield (CFU/mM Fe(II)) was 112% of WT in ∆cbcBA, and deletion of cbcL (an unrelated bc-cytochrome essential near −0.15 V) in ΔcbcBA increased yield to 220%. Together with ImcH, which is required at high redox potentials, CbcBA represents a third cytoplasmic membrane oxidoreductase in G. sulfurreducens. This expanding list shows how metal-reducing bacteria may constantly sense redox potential to adjust growth efficiency in changing environments.

中文翻译:

Geobactersulfurreducens 内膜细胞色素 CbcBA 控制接近呼吸能量极限的电子转移和生长产量

Geobacterthioreducens利用细胞外电子受体,如 Mn(IV)、Fe(III)、同营养伙伴和电极,与标准氢电极 (SHE) 相比,其变化范围为 +0.4 至 -0.3 V,代表一个势能跨度,需要高度分支的电子转移链。在这里,我们描述了 CbcBA, 当醋酸盐是电子供体时,它是一种在呼吸热力学极限附近必不可少的bc型细胞色素。与 SHE 相比,缺乏cbcBA的突变体在 -0.21 V 时停止了 Fe(III) 还原,无法将电子转移到 -0.21 和 -0.28 V 之间的电极,并且无法还原最终 10%–35% 的 Fe(III) 矿物。由于在 Fe(III) 还原过程中氧化还原电位降低,cbcBA在调节剂 BccR 的帮助下被诱导成为 G.thioreducens 中表达最高的基因之一。Δ cbcBA中的生长产量 (CFU/mM Fe(II)) 为 WT 的 112%,Δ cbcBA中cbcL的缺失(一种不相关的bc -细胞色素在 -0.15 V 附近必不可少)产量提高到 220%。与在高氧化还原电位下所需的 ImcH 一起,CbcBA 代表了硫还原菌中的第三种细胞质膜氧化还原酶。这个不断扩大的列表显示了金属还原细菌如何不断感知氧化还原电位,从而在不断变化的环境中调整生长效率。
更新日期:2021-10-25
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