Deciphering Molecular Factors That Affect Electron Transfer at the Cell Surface of Electroactive Bacteria: The Case of OmcA from Shewanella oneidensis MR-1

Abstract

Multiheme cytochromes play a central role in extracellular electron transfer, a process that allows microorganisms to sustain their metabolism with external electron acceptors or donors. In Shewanella oneidensis MR-1, the decaheme cytochromes OmcA and MtrC show functional specificity for interaction with soluble and insoluble redox partners. In this work, the capacity of extracellular electron transfer by mutant variants of S. oneidensis MR-1 OmcA was investigated. The results show that amino acid mutations can affect protein stability and alter the redox properties of the protein, without affecting the ability to perform extracellular electron transfer to methyl orange dye or a poised electrode. The results also show that there is a good correlation between the reduction of the dye and the current generated at the electrode for most but not all mutants. This observation opens the door for investigations of the molecular mechanisms of interaction with different electron acceptors to tailor these surface exposed cytochromes towards specific bio-based applications.

Key findings

• ▸Amino acid mutations can alter the redox properties of OmcA without affecting its ability to transfer electrons.
• ▸There is a good correlation between the reduction of methyl orange dye and the current generated at the electrode for most mutants.
• ▸The results suggest that molecular mechanisms of interaction with different electron acceptors can be tailored for specific bio-based applications.

Keywords

Identifiers

DOI

10.3390/microorganisms11010079

Journal

Microorganisms

Year

2022