Soluble Mn(III) represents an important yet overlooked oxidant in marine and freshwater systems. The molecular mechanism of microbial Mn(III) reduction, however, has yet to be elucidated. Extracellular reduction of insoluble Mn(IV) and Fe(III) oxides by the metal‐reducing γ‐proteobacterium Shewanella oneidensis involves inner (CymA) and outer (OmcA) membrane‐associated c‐type cytochromes, the extracellular electron conduit MtrCAB, and GspD, the secretin of type II protein secretion. CymA, MtrCAB and GspD mutants were unable to reduce Mn(III) and Mn(IV) with lactate, H₂, or formate as electron donor. The OmcA mutant reduced Mn(III) and Mn(IV) at near wild‐type rates with lactate and formate as electron donor. With H₂ as electron donor, however, the OmcA mutant was unable to reduce Mn(III) but reduced Mn(IV) at wild‐type rates. Analogous Fe(III) reduction rate analyses indicated that other electron carriers compensated for the absence of OmcA, CymA, MtrCAB and GspD during Fe(III) reduction in an electron donor‐dependent fashion. Results of the present study demonstrate that the S. oneidensis electron transport and protein secretion components involved in extracellular electron transfer to external Mn(IV) and Fe(III) oxides are also required for electron transfer to Mn(III) and that OmcA may function as a dedicated component of an H₂ oxidation‐linked Mn(III) reduction system.

中文翻译：

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电子转移和蛋白质分泌途径参与了希瓦氏菌的还原锰（III）。

可溶性Mn（III）是海洋和淡水系统中一种重要但被忽视的氧化剂。然而，微生物Mn（III）还原的分子机制尚未阐明。金属还原性γ-变形杆菌S hewanella oneidensis的胞外还原性不溶性Mn（IV）和Fe（III）氧化物涉及膜内（CymA）和膜外（OmcA）相关的c型细胞色素，细胞外电子导管MtrCAB和GspD，II型蛋白质分泌的分泌素。CymA，MtrCAB和GspD突变体无法以乳酸，H ₂或甲酸作为电子供体来还原Mn（III）和Mn（IV）。OmcA突变体以乳酸和甲酸作为电子供体，以接近野生型的速率还原了Mn（III）和Mn（IV）。与H ₂然而，作为电子供体，OmcA突变体无法还原Mn（III），但能以野生型速率还原Mn（IV）。类似的Fe（III）还原速率分析表明，其他电子载流子以依赖电子供体的方式补偿了Fe（III）还原过程中OmcA，CymA，MtrCAB和GspD的缺失。本研究结果表明，S 。电子传递到Mn（III）时也需要oneidensis电子传递和蛋白质分泌成分，涉及细胞外电子转移到外部Mn（IV）和Fe（III）氧化物中，OmcA可能充当H ₂氧化的专用成分-连接的Mn（III）还原系统。