FIGURE 6.

Knock-down of IFR1 in the boosts hydrogen production in the high hydrogen producer mutant stm6. (A) Immunoblot analysis of IFR1 accumulation in stm6 and stm6_IFR1kd cultivated under sulfur-limiting conditions. Different amounts of total protein (1X; 1.5X; and 2X) were used for immunodetection of IFR1 (αIFR1) with a colloidal Coomassie stain (CBB) serving as a loading control. Results from densitometric signal analysis (dens.) are indicated. (B) Relative time-dependent H₂ yields of the stm6 parental strain (black curve) and stm6_IFR1kd (gray curve) with the final yield in stm6 set to 100%. Error bars represent the standard error (three biological replicates including technical triplicates, n = 9). (C) Maximum quantum yield of PSII determined after dark incubation (Fv/Fm) determined in cultures of stm6 (black bars) and stm6_IFR1kd (gray bars) exposed to sulfur starvation. Standard errors, shown as error bars are derived from three biological replicates including technical duplicates (n = 6). Except for t₀, differences between stm6 and stm6_IFR1kd were significant according to a two-tailed Student’s t-test (p < 0.05).