电子穿梭体对不同希瓦氏菌介导铁氧化物生物还原的特异性影响

Impact of Electron Shuttles on the Bioreduction of Iron Oxides Mediated by Different Shewanella Species

摘要

异化铁还原过程在环境修复（重金属固定）等领域可发挥重要作用。电子穿梭体（electron shuttles， ES）是调控异化铁还原菌（dissimilatory iron reducing bacteria， DIRB）胞外电子传递（extracellular electron transfer，EET）的关键介质，但其效能可能存在显著的菌种特异性。为揭示希瓦氏菌属（Shewanella）内不同菌种对ES的响应差异及机制，本研究系统比较了5-甲基吩嗪硫酸甲酯（PMS）、还原型辅酶I（NADH）及还原型辅酶 II（NADPH）对两种典型希瓦氏菌（Shewanella oneidensis MR-1与Shewanella aquimarina）介导赤铁矿（α-Fe₂O₃）生物还原的调控作用。研究发现，ES的催化效能表现出强烈的菌种依赖性：PMS能特异性地高效驱动S. aquimarina的铁还原过程，使亚铁（Fe²⁺）产量高达 160mg/L，较对照组提升约 8 倍；而 S. oneidensis MR-1 则能通过其多样化的 EET网络，利用 NADH 或 PMS，使 Fe²⁺产量分别提升至120mg/L、130mg/L（较对照组提升约5倍），但对NADPH无显著响应。比较基因组分析揭示，两者 EET 差异的遗传基础为：S. oneidensis MR-1 包含完整的 Mtr 金属还原通道基因簇，而S. aquimarina缺失MtrA等关键基因，却富集6个OmcA/MtrC家族细胞色素基因。这种EET的差异可能与菌株特异性的胞外细胞色素含量、电子传递链结构以及ES与细胞表面的构效关系密切相关。本研究深化了微生物-矿物界面电子传递机制的理解，为通过增强异化铁还原以促进污染场地的重金属固定与修复提供了科学依据。

Abstract

Dissimilatory iron reduction can play a significant role in environmental remediation, such as in the immobilization of heavy metals. Electron shuttles (ES) are key mediators regulating extracellular electron transfer (EET) in dissimilatory iron-reducing bacteria (DIRB), yet their efficacy may exhibits significant species-specificity. To elucidate the differential response mechanisms within the Shewanella genus, this study systematically investigated the regulatory effects of phenazine methosulfate (PMS), reduced nicotinamide adenine dinucleotide (NADH), and its phosphate form (NADPH) on the bioreduction of hematite (α -Fe₂O₃) by Shewanella oneidensis MR-1 and Shewanella aquimarina. Results revealed a strong species-dependent catalytic performance of ES. PMS specifically and efficiently drove the iron reduction by S. aquimarina, achieving a high ferrous iron concentration of 160mg/L, an approximate 8-fold increase compared to the control. In contrast, S. oneidensis MR-1 leveraged its versatile EET network to synergistically utilize both NADH and PMS, resulting in a ≈5-fold increase in ferrous iron production (≈120mg/L、130mg/L), but showed no significant response to NADPH. Genome comparison analysis further revealed that S. aquimarina genome lacks the key gene of Mtr metal reduction channel, but is rich (n=6) in multiple copies of OmcA family cytochrome genes. These differences in EET may be related to strain-specific extracellular cytochrome content, electron transport chain structure and structure-activity relationship between shuttle molecules and cell surface. This study deepens the understanding of electron transfer mechanisms at the microbe-mineral interface , providing a scientific basis for the remediation of contaminated sites via enhancing dissimilatory iron reduction to promote heavy metal immobilization.

关键词

电子穿梭体 / 希瓦氏菌 / Fe（III）氧化物 / 胞外电子传递 / 菌种特异性

Key words

Electron Shuttles / Shewanella / Fe(III) Oxides / Extracellular Electron Transfer / Strain Specificity

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基金资助

滨州魏桥国科高等技术研究院碳中和技术体系创新研究项目(GYY-NYHJ-2023-WT-002)