FIG. 3.

Effect of HupE and HupE2 on the hydrogenase activity of the E. coli HYD723 nik mutant. Wild-type strain MC4100 and nik mutant HYD723 expressing pBAD-derivative plasmid pBADE1 (hupE) or pBADE2 (hupE2) or control plasmid pBAD18-Kan were assayed for hydrogenase activity in anaerobic cultures grown in a glycerol-fumarate medium for 5 h with 200 μM arabinose or without inducer. Values for hydrogenase activities are averages of results from four independent assays, with error bars corresponding to standard errors (SE). prot, protein.