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Article

Crossing the Wall: Characterization of the Multiheme Cytochromes Involved in the Extracellular Electron Transfer Pathway of Thermincola ferriacetica

Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
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Academic Editor: Xiaobo Liu
Microorganisms 2021, 9(2), 293; https://doi.org/10.3390/microorganisms9020293
Received: 31 December 2020 / Revised: 25 January 2021 / Accepted: 27 January 2021 / Published: 31 January 2021
Bioelectrochemical systems (BES) are emerging as a suite of versatile sustainable technologies to produce electricity and added-value compounds from renewable and carbon-neutral sources using electroactive organisms. The incomplete knowledge on the molecular processes that allow electroactive organisms to exchange electrons with electrodes has prevented their real-world implementation. In this manuscript we investigate the extracellular electron transfer processes performed by the thermophilic Gram-positive bacteria belonging to the Thermincola genus, which were found to produce higher levels of current and tolerate higher temperatures in BES than mesophilic Gram-negative bacteria. In our study, three multiheme c-type cytochromes, Tfer_0070, Tfer_0075, and Tfer_1887, proposed to be involved in the extracellular electron transfer pathway of T. ferriacetica, were cloned and over-expressed in E. coli. Tfer_0070 (ImdcA) and Tfer_1887 (PdcA) were purified and biochemically characterized. The electrochemical characterization of these proteins supports a pathway of extracellular electron transfer via these two proteins. By contrast, Tfer_0075 (CwcA) could not be stabilized in solution, in agreement with its proposed insertion in the peptidoglycan wall. However, based on the homology with the outer-membrane cytochrome OmcS, a structural model for CwcA was developed, providing a molecular perspective into the mechanisms of electron transfer across the peptidoglycan layer in Thermincola. View Full-Text
Keywords: Thermincola; multiheme c-type cytochromes; extracellular electron transfer; electroactive organisms; Gram-positive bacteria Thermincola; multiheme c-type cytochromes; extracellular electron transfer; electroactive organisms; Gram-positive bacteria
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    Link: https://www.dropbox.com/s/8ohelen9i8xbv7u/Supplementary%20Material_revised_final.docx?dl=0
    Description: In a single word file: Figure S1: Sequence alignment used to build the CwcA homology based mode, Figure S2: OcwA from T. ferriacetica. Figure S3: SDS-PAGE of (a) ImdcA and (b) PdcA stained with blue-safe, Fig-ure S4: Aminoacid sequence of (a) ImdcA and (b) PdcA, Figure S5: Raw voltammogram ob-tained by cyclic voltammetry for (a) ImdcA and (b) PdcA.
MDPI and ACS Style

Faustino, M.M.; Fonseca, B.M.; Costa, N.L.; Lousa, D.; Louro, R.O.; Paquete, C.M. Crossing the Wall: Characterization of the Multiheme Cytochromes Involved in the Extracellular Electron Transfer Pathway of Thermincola ferriacetica. Microorganisms 2021, 9, 293. https://doi.org/10.3390/microorganisms9020293

AMA Style

Faustino MM, Fonseca BM, Costa NL, Lousa D, Louro RO, Paquete CM. Crossing the Wall: Characterization of the Multiheme Cytochromes Involved in the Extracellular Electron Transfer Pathway of Thermincola ferriacetica. Microorganisms. 2021; 9(2):293. https://doi.org/10.3390/microorganisms9020293

Chicago/Turabian Style

Faustino, Marisa M., Bruno M. Fonseca, Nazua L. Costa, Diana Lousa, Ricardo O. Louro, and Catarina M. Paquete 2021. "Crossing the Wall: Characterization of the Multiheme Cytochromes Involved in the Extracellular Electron Transfer Pathway of Thermincola ferriacetica" Microorganisms 9, no. 2: 293. https://doi.org/10.3390/microorganisms9020293

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