Fig. 5. A diversity of syntrophs known to produce H₂ and/or formate as an interspecies electron carrier encode for pilin monomers likely to yield electrically conductive pili.

Position of aromatic amino acids designated in magenta and the largest gap that lacks aromatic amino acids designated in blue. The full protein sequence alignment for each pilin can be found in Supplementary Fig. 6. Each of the pilins meets the empirical criteria derived from previous studies [33] of: (1) aromatic amino acids located in the key positions required for conductivity in G. sulfurreducens e-pili; (2) the abundance of aromatic amino acids greater than 9%; and (3) no aromatic-free gaps of greater than 40 amino acids.