Abstract:[Objective] The main objectives of this study were (i) to investigate the role of Mcc, a periplasmic monohemecytochrome c, in the extracellular electron transfer process of Shewanella decolorationis S12, and (ii) to provide new information for a complete understanding of bacterial extracellular electron transfer. [Methods] An mcc-mutant was created by using a suicide plasmid. The planktonic and biofilm growth of the mutant and wild type strains were compared by using cell optical density and confocal laser scanning microscope. Furthermore, the extracellular electron transfer capacities including electrode respiration, iron reduction and azo dye reduction of the two strains were analyzed. [Results] Although no significant difference was detected in iron and azo dye reduction between the wild type and mutant strains, mutant strain showed 34.1% decrease in electrode respiration capacity when using electrode as electron acceptor in microbial fuel cells in comparison with the wild type strain. In microbial fuel cells, the mcc-mutant showed similar planktonic growth profile but lower electrode biofilm forming capacity compared to the wild type strain. [Conclusion] The results demonstrated that Mcc played an important and specific role in the periplasmic electron transfer of S. decolorationis S12 electrode respiration, Mcc-deficiency caused significantly decrease in the electrode respiration and biofilm growth capacities of S. decolorationis S12.
