Figure 4

Relative expression of [FeFe] hydrogenases and nifH genes determined by RT-qPCR of Clostridium butyricum CWBI 1009 during unregulated-pH glucose fermentation. Western blot analysis for the NifH subunit. (A) Fold change in the expression level of hydA2, hydA8, hydB2, hydB3, nifH genes during the unregulated-pH glucose fermentation determined by RT-qPCR. The values correspond to the pH 6.3 (test) sample) versus pH 7.3 (control) sample). (B) Basal expression levels of hydA2, hydA8, hydB2, hydB3, nifH gene transcripts during the unregulated-pH glucose fermentation. The values correspond to the late exponential growth stage that refers to the peak in H₂ production at pH 6.3. Expression level is shown as number of cDNA copies per 1,000 cDNA copies of 16S rRNA. (C) Western blot analysis of the crude cellular extracts taken during the unregulated-pH glucose fermentation. Time of incubation corresponds to the different growth stages starting from the beginning of the experiment, until the pH dropped to a level of about 4.5. The arrow indicates pH 6.3. Pc: positive control.