Transcriptional levels of selected genes in strains MGB874 and 874ΔrocG. The strains MGB874 (A) and 874∆rocG (B) were transformed with pHYS237, and cultured by the pH-Stat fermentation. Fermentation without pH control was done as a reference (a). The pH was adjusted to 7.2 by addition of NaOH (b) or aqueous NH3 (c). RNA was isolated from the cells at the 24 h of the cultivation time (indicated by arrows in Figure 4), and expression level of htrB, nrgA, gltA and citB were determined by qRT-PCR. The transcriptional levels are expressed relative to those of 16S rRNA. Error bars represent standard deviations (n=3).