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Molecular insights on bioelectrochemical technologies

A new evolutionary vision on cytochromes c obtained from studies using a Gram-positive bacterium

The understanding of the extracellular electron transfer has become a priority in the scientific and industry communities, to improve bioelectrochemical systems toward their commercial implementation. Electroactive organisms can couple the oxidation of organic matter to the reduction of an electrode in bioelectrochemical systems. This capacity, known as extracellular electron transfer, allows their use in sustainable technologies for electricity production, wastewater treatment and bioremediation.

Ricardo O. Louro Lab focuses on the understanding of extracellular electron transfer processes of electroactive organisms. Thermophilic Gram-positive bacteria are promising organisms to be used in bioelectrochemical systems for the production of electrical energy from wastewater treatment. In a paper recently published by the journal mBio, ITQB NOVA researchers Nazua Costa, Marisa Faustino, Miguel Teixeira, Catarina Paquete and Ricardo Louro, in collaboration with researchers from the Albert-Ludwigs-Universität Freiburg and the Aix-Marselle Université, revealed that the terminal reductase OcwA from Thermincola potens strain JR is a multiheme cytochrome c that, in addition to solid electron acceptors, can also reduce soluble electron shuttles and oxyanions. This is a novelty within this class of proteins.

This work provides the first insight into the molecular mechanisms of terminal reductases from thermophilic Gram-positive bacteria, a knowledge that is crucial for the implementation of bioelectrochemical systems. The three-dimensional structure of OcwA is the first structural information obtained for a multiheme cytochrome from a Gram-positive bacterium. It shows that OcwA is unrelated to other structurally characterized outer-membrane cytochromes. Instead, it is structurally and functionally related to multiheme cytochromes involved in the biogeochemical cycles of nitrogen and sulphur. The research suggests that terminal reductases of soluble and insoluble substrates are evolutionarily related, providing novel insights into the evolutionary pathways of multiheme cytochromes c.

Original paper:

N.L. Costa, B. Hermann, V. Fourmond, M. Faustino, M. Teixeira, O. Einsle, C.M. Paquete, R.O. Louro


How Thermophilic Gram-Positive Organisms Perform Extracellular Electron Transfer: Characterization of the Cell Surface Terminal Reductase OcwA

mBio, DOI 10.1128/mBio.01210-19



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