Figure 6

Relative expression of [FeFe] hydrogenases and nifH genes determined by RT-qPCR for Clostridium butyricum CWBI 1009 during fixed pH 7.3 and 5.2 glucose fermentations. (A) Fold change in the expression level of the hydA2, hydA8, hydB2, hydB3, nifH genes during fixed pH 7.3 glucose fermentation. (B) Fold change in the expression level of hydA2, hydA8, hydB2, hydB3, nifH genes during fixed pH 5.2 glucose fermentation. For (A) and (B) the values correspond to the late exponential (test sample) versus early exponential growth phase (control sample). (C) Fold change in the expression level of hydA2, hydA8, hydB2, hydB3, nifH genes during the fixed pH 5.2 versus 7.3 glucose fermentations. The values correspond to the late exponential growth stages from both experiments that correspond to the peak in H₂ production; the culture at fixed pH 5.2 was used as a test sample, while pH 7.3 was a control sample. (D) Basal expression levels of the hydA2, hydA8, hydB2, hydB3, nifH gene transcripts during fixed-pH glucose fermentations. The expression level is shown as the number of cDNA copies per 1,000 cDNA copies of 16S rRNA. The values correspond to the late exponential growth stages from both experiments that correspond to the peak in H₂ production.