Figure 7.

Relative hydrogenase evolution activities of heterologous expression constructs bearing the wild type vs. doubly-substituted A. macleodii hydrogenase. pIY007/pIY003 compares the doubly-substituted enzyme (DS) and the wild type (WT) enzyme produced by the hydrogenase operon as driven by P_TRC and transformed into the hydrogenase-free E. coli K12 strain FTD147. pIY038/pIY033 compares DS and WT enzymes produced by the hydrogenase operons as driven by P_T7 and transformed into the hydrogenase-free E. coli BL21(DE3)ΔH₄ derivative. pCM012/pRC41-4 compares the hydrogenase operons driven by 4 P_TRC promoters interspersed in the operon and integrated into an otherwise hydrogenase-free S. elongatus cyanobacterial strain. Relative activities are plotted on a log scale over a 50-fold range. Error bars represent one geometric standard error of the geometric mean.