FIG 4.

Electron uptake profile of hydrogenase deletion mutant (Δhyd) is similar to M. barkeri wild-type washed culture experiments and is diminished in the presence of BES. (A) Cyclic voltammetry (1-mV/s scan rate over a range of −800 to 200 mV) showing the current-voltage relationship for washed cultures of the Δhyd mutant compared with spent medium from the Δhyd mutant and blank medium abiotic controls. With the exception of abiotic controls (run preexperiment), all cyclic voltammetry was performed postchronoamperometry (shown in Fig. 3). (B) Comparing washed culture experiment cyclic voltammetry, hydrogen addition (headspace of 80%/20% H₂/CO₂) results in no change in the electron uptake features observed; however, the addition of 7 mM BES abolishes the electron uptake feature.