Figure 2

Characterization of synthetic hydrogen production pathway A.) Western blot of Strep-II tagged hydrogenase expression. B.) In vitro hydrogen production from E. coli strains expressing various hydrogenases, measured by the methyl viologen in vitro assay [18]. C.a. = C. acetobutylicum, C.s. = C. saccharobutylicum, C.r. = C. reinhardtii, S.o. = Shewanella oneidensis. C.) Glucose-dependence of hydrogen production. Here and below, in vivo and in vitro hydrogen production values are in units of μmol hydrogen/ml of E. coli culture, normalized to an OD₆₀₀ of 0.15 unless otherwise stated. Assays were performed in triplicate, with error bars indicating standard deviation. D.) In vivo hydrogen production from E. coli strains expressing all combinations of the four hydrogenases vs. three ferredoxins from C. acetobutylicum, Spinacia olearcea (Sp.o), and Zea mays (Zm). E.) In vivo hydrogen production from the C. acetobutylicum hydrogenase paired with combinations of three ferredoxins and three PFOR genes.