Fig. 3: Electrochemical measurements confirm robust extracellular electron-uptake phenotype for 5 S. oneidensis mutants identified by our high-throughput screen (δSO_0181, δSO_0400, δSO_0841, δSO_03660 and δSO_03662; (δ indicates a transposon-insertion mutant)).

δSO_03662 was implicated in electron uptake by the AHDS_red oxidation assay. However, at the time of collecting data for panels a, b, we were unable to retrieve δSO_03662 from the S. oneidensis whole-genome-knockout collection, so later constructed a clean deletion mutant to collect data for panel c. Hence, we talk about four mutants in panels a, b, but 5 in panel c. We were later able to retrieve δSO_3662 mutant and retested it in the AHDS_red oxidation assay prior to submitting this article. The δmtrA control mutant in panels a, b shows significant derivation from wild type, but the current range is too small to be drawn clearly, so is marked with arrows. a We measured the cathodic biological current for 18 S. oneidensis mutants that produced AHDS_red oxidation failure for unknown reasons, control mutants (δfccA, δmtrA, δmtrC, and δnapG), and wild type (WT). In total, 6 gene-disruption mutants, four of them previously uncharacterized, produced robust reductions in cathodic current. The region corresponding to wild-type currents and one standard deviation is shaded in blue. ANOVA results indicated that there was a significant variation in means of the strains from one another (F-value = 5.94; Pr(>F) = 2.34 × 10⁻⁹), while individual comparisons specifically revealed δSO_0181, δmtrA, δSO_0841, δSO_0400, δSO_3660, and δmtrC to all display significantly lower cathodic currents (p < 0.05) than WT. b However, three of the six robust electron-uptake mutants (three of the four previously uncharacterized disruption mutants) do not have a significant effect on anodic current production (electron deposition), the well-characterized phenotype of S. oneidensis. The range of wild-type current values and a standard deviation from the mean is shaded in blue. Analysis of anodic current values (F-value = 5.801, Pr(>F) = 2.10 × 10⁻¹⁰) revealed that of the four previously uncharacterized disruption mutants, only δSO_0841 shows anodic current production different from WT (p < 0.05). c Gene deletion (indicated by Δ) confirms the electron uptake phenotype of five mutants. Complementation of the deleted gene restores electron uptake phenotype. Further information on electrochemical methods can be seen in Materials and methods. Data are available in ref. ⁵³.