Significance Cellular respiration process in dissimilatory metal-reducing bacteria is coupled to electron transfer. In Shewanella species, a decaheme cytochrome MtrF transfers electrons to extracellular insoluble substrates, such as Fe(III) and Mn(III/IV). Using the atomic coordinates of the MtrF crystal structure and analyzing interactions with the protein environments, we calculated the redox potential ( E m ) values of the 10 hemes in MtrF. The E m profiles show how the electron transfer pathways proceed in MtrF. We showed that, when MtrF is reduced, the direction of the ET pathway switches, and bound flavin becomes the terminal electron acceptor.