In-vivo identification of direct electron transfer from Shewanella oneidensis MR-1 to electrodes via outer-membrane OmcA-MtrCAB protein complexes
In-vivo identification of direct electron transfer from Shewanella oneidensis MR-1 to electrodes via outer-membrane OmcA-MtrCAB protein complexes
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DOI：
10.1016/j.electacta.2011.03.076
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发表时间：
2011-06-30
影响因子：
6.6
通讯作者：
Hashimoto, Kazuhito
中科院分区：
文献类型：
--
作者：
Okamoto, Akihiro;Nakamura, Ryuhei;Hashimoto, Kazuhito
由于在全细胞系统中体内电化学的复杂性，希瓦氏菌属细菌的直接电子转移（DET）特性尚未详细解决。在这里，我们报告的氧化还原信号指示DET属性的希瓦氏菌oneidensis MR-1的生物膜的循环伏安法（CV）与一系列的突变体和化学标记技术的体内分配。C型细胞色素缺失突变体形成的单层生物膜的CV测定（Delta mtrA、Delta mtrB、Delta mtrC/Delta omcA和Delta cymA）和菌毛蛋白（Δ pilD），荚膜多糖（Delta SO 3177）和甲萘醌（Δ menD）生物合成蛋白质证明，在50 mV的中点电位下的电化学氧化还原信号（相对于SHE）提示十血红素细胞色素的外膜结合OmcA-MtrCAB蛋白复合物，并且不涉及内膜结合CymA蛋白或分泌的甲基萘醌。利用一氧化氮对c型细胞色素血红素基团的特异性结合亲和力，我们进一步证实了这一结论。DET过程的非均相标准速率常数估计为300 +/-10 s（-1），这比先前报道的通过核黄素的电子穿梭过程高两个数量级。使用不能产生荚膜多糖的突变体（Delta SO 3177）的实验揭示OmcA-MtrCAB复合物的DET性质不受绝缘和亲水性胞外多糖的影响。因此，在生理条件下，S. oneidensis MR-1利用高密度的外膜结合OmcA-MtrCAB复合物作为DET电极呼吸过程的末端还原酶。(C)2011爱思唯尔有限公司版权所有。
The direct electron-transfer (DET) property of Shewanella bacteria has not been resolved in detail due to the complexity of in vivo electrochemistry in whole-cell systems. Here, we report the in vivo assignment of the redox signal indicative of the DET property in biofilms of Shewanella oneidensis MR-1 by cyclic voltammetry (CV) with a series of mutants and a chemical marking technique. The CV measurements of monolayer biofilms formed by deletion mutants of c-type cytochromes (Delta mtrA, Delta mtrB, Delta mtrC/Delta omcA, and Delta cymA), and pilin (Delta pilD), capsular polysaccharide (Delta SO3177) and menaquinone (Delta menD) biosynthetic proteins demonstrated that the electrochemical redox signal with a midpoint potential at 50 mV (vs. SHE) was clue to an outer-membrane-bound OmcA-MtrCAB protein complex of decaheme cytochromes, and did not involve either inner-membrane-bound CymA protein or secreted menaquinone. Using the specific binding affinity of nitric monoxide for the heme groups of c-type cytochromes, we further confirmed this conclusion. The heterogeneous standard rate constant for the DET process was estimated to be 300 +/- 10s(-1), which was two orders of magnitude higher than that previously reported for the electron shuttling process via riboflavin. Experiments using a mutant unable to produce capsular polysaccharide (Delta SO3177) revealed that the DET property of the OmcA-MtrCAB complex was not influenced by insulating and hydrophilic extracellular polysaccharide. Accordingly, under physiological conditions, S. oneidensis MR-1 utilizes a high density of outer-membrane-bound OmcA-MtrCAB complexes as terminal reductases for the DET electrode-respiring process. (C) 2011 Elsevier Ltd. All rights reserved.