Figure 4.

RyjB expression is regulated by PhoP. A. Amount of phoP mRNA upon acid stress (pH adjusted by 50-mM HOMOPIPES) was estimated by RT-qPCR analysis. 5S rRNA gene was taken as internal control for the normalization of the amount of phoP mRNA at each time point. Accumulation of phoP mRNA at 0 min was set as 1 and relative amount of phoP at other time point was calculated. B. PhoP accumulation after acid stress (pH adjusted by 50 mM sodium acetate) in wild type cells was measured by western blotting. The number under each lane represents the relative amount of PhoP protein when compared with 0-min sample, which was set as 1. Ribosomal protein S1 was taken as loading control. C. Acid stress was given to mid-exponential phase (OD₆₀₀ = 0.4) wild type and ΔphoP cells. Total RNA was isolated from the cells at indicated times after acid stress and was utilized for RT-qPCR analysis. Expression of 5S rRNA gene was utilized as internal control.