Vinales Jorge, Sackett Joshua, Trutschel Leah, Amir Waleed, Norman Casey, Leach Edmund, Wilbanks Elizabeth, Rowe Annette
Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, USA.
Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA.
Microorganisms. 2022 Jun 14;10(6):1219. doi: 10.3390/microorganisms10061219.
Extracellular electron transfer (EET), the process that allows microbes to exchange electrons in a redox capacity with solid interfaces such as minerals or electrodes, has been predominantly described in microbes that use iron during respiration. In this work, we characterize the physiology, genome, and electrochemical properties of two obligately heterotrophic marine microbes that were previously isolated from marine sediment cathode enrichments. Phylogenetic analysis of isolate 16S rRNA genes showed two strains, SN11 and FeN1, belonging to the genus Strain SN11 was found to be nearly identical to L2-TR, and strain FeN1 was most closely related to 908087. Each strain had a relatively small genome (~2.8-2.9 MB). Phenotypic similarities among FeN1, SN11, and the studied strains include being Gram-negative, motile, catalase- and oxidase-positive, and rod-shaped. Physiologically, all strains appeared to exclusively use amino acids as a primary carbon source for growth. This was consistent with genomic observations. Each strain contained 17 to 22 proteins with heme-binding motifs. None of these were predicted to be extracellular, although seven were of unknown localization and lacked functional annotation beyond cytochrome. Despite the lack of homology to known EET pathways, both FeN1 and SN11 were capable of sustained electron uptake over time in an electrochemical system linked to respiration. Given the association of these strains with electro-active biofilms in the environment and their lack of autotrophic capabilities, we predict that EET is used exclusively for respiration in these microbes.
细胞外电子转移（EET）是一种使微生物能够以氧化还原能力与矿物或电极等固体界面交换电子的过程，主要在呼吸过程中使用铁的微生物中得到描述。在这项工作中，我们对先前从海洋沉积物阴极富集物中分离出的两种专性异养海洋微生物的生理学、基因组和电化学特性进行了表征。对分离的16S rRNA基因进行系统发育分析，结果显示有两个菌株，SN11和FeN1，属于 属。发现菌株SN11与L2-TR几乎相同，菌株FeN1与908087关系最为密切。每个菌株的基因组相对较小（约2.8-2.9 MB）。FeN1、SN11与所研究菌株之间的表型相似性包括革兰氏阴性、有运动性、过氧化氢酶和氧化酶阳性以及杆状。在生理上，所有菌株似乎都仅将氨基酸用作生长的主要碳源。这与基因组观察结果一致。每个菌株含有17至22个带有血红素结合基序的蛋白质。尽管其中七个的定位未知且除细胞色素外缺乏功能注释，但预计这些蛋白质均无细胞外的。尽管与已知的EET途径缺乏同源性，但FeN1和SN11在与呼吸相关的电化学系统中均能够随着时间的推移持续摄取电子。鉴于这些菌株与环境中电活性生物膜的关联以及它们缺乏自养能力，我们预测EET在这些微生物中仅用于呼吸作用。
