Extracellular electron transfer in fermentative bacterium Anoxybacter fermentans DY22613T isolated from deep-sea hydrothermal sulfides.
Extracellular electron transfer in fermentative bacterium Anoxybacter fermentans DY22613T isolated from deep-sea hydrothermal sulfides.
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DOI：
10.1016/j.scitotenv.2020.137723
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发表时间：
2020-03
期刊：
影响因子：
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通讯作者：
Xi Li;Xiang Zeng;Donghua Qiu;Zhao Zhang;Xiaobo Zhang;Z. Shao
中科院分区：
文献类型：
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作者：
Xi Li;Xiang Zeng;Donghua Qiu;Zhao Zhang;Xiaobo Zhang;Z. Shao
异化Fe（III）还原菌（DIRBs）通过胞外电子传递（EET）将胞外Fe（III）还原为Fe（II），在Fe（III）的生态地球化学循环中发挥重要作用。先前的研究已经注意到参与EET的多血红素型细胞色素（MHC）通过氧化还原型DIRB的关键作用，并提出通过使用氧化还原电子穿梭（例如，黄素）或Fe（III）-螯合。然而，关于发酵DIRB的EET的知识是极其稀缺的。Anoxybacter fermentansDY 22613 T是一株典型的深海热液硫化物中分离到的能发酵的DIRB，它能利用可溶性柠檬酸铁和固体含铁矿物作为胞外电子受体。与利用MHC的寄生型DIRB不同，该菌株缺乏介导EET的MHC。此外，它没有通过Fe（III）螯合介导间接EET。尽管如此，编码氧化还原分子生物合成途径的基因（例如，在其基因组中发现了一种新的EET（flavins）基因，其基因表达随Fe（III）还原而上调，表明氧化还原分子可能介导了该菌株的间接EET。随后的生理生化试验进一步证明，内源核黄素是该菌株间接EET的主要电子穿梭途径，甲基萘醌、吲哚在此过程中起辅助作用。此外，该菌株还可以利用外源腐殖酸促进间接EET。外源性和内源性氧化还原分子共同介导发酵A. fermentansDY 22613 T，扩展了我们对发酵DIRB的EET的认识，并将有助于更好地理解其在铁的生物地球化学循环中的生态作用。
Dissimilatory Fe(III)-reducing bacteria (DIRBs) could reduce extracellular Fe(III) to Fe(II) via extracellular electron transfer (EET), playing an important role in biogeochemical cycling of Fe(III). Previous studies have noted the key role of multi-hemec-type cytochromes (MHCs) involved in EET by respiratory-type DIRBs, and proposed indirect electron transfer through the use of redox electron shuttles (e.g., flavins) or Fe(III)-chelation. However, knowledge about the EET of fermentative DIRBs was vitally scarce. Here,Anoxybacter fermentansDY22613Tis a typical fermentative DIRB isolated from deep-sea hydrothermal sulfides, and it could utilize soluble Fe(III)-citrate and solid Fe(III)-bearing minerals as extracellular electron acceptors. Unlike respiratory-type DIRBs that utilize MHCs, this strain lacked MHCs to mediate EET. Besides, it did not adopt Fe(III)-chelation to mediate indirect EET. Nonetheless, genes encoding biosynthesis pathway of redox molecules (e.g., flavins) were found in its genome and their gene expression was up-regulated with Fe(III) reduction, suggesting redox molecules may mediate indirect EET by this strain. Subsequent physiological and biochemical tests further demonstrated endogenous riboflavin acted as main electron shuttles to mediate indirect EET by this strain, and menaquinone, indole played an assistant role in this process. Besides, this strain could employ exogenous humic acids to facilitate indirect EET. The mode of exogenous and endogenous redox molecules to co-mediate indirect EET by fermentativeA. fermentansDY22613T, expands our knowledge about EET of fermentative DIRBs, and would contribute to better understand its ecological role in the biogeochemistry cycle of iron.