Reduction of Fe(III) (hydr)oxide, ferric citrate, or AQDS by S. oneidensis MR-1 mutants defective in electron transfer. (A) Reduction of 0.5 mM Fe(III) (hydr)oxide; (B) reduction of 1 mM ferric citrate; (C) reduction of 1 mM AQDS. Symbols: ▪, wild-type strain MR-1; ▾, omcB mutant DKN247; ▴, mtrB mutant DKN248; •, menF mutant DKN249; ⋄, cymA mutant DKN250. The error bars indicate the ranges for duplicate cultures for the iron reduction experiments and the standard deviations for triplicate cultures for the AQDS reduction experiment.