The relative expression of the hdcA gene at various pH conditions
at the end of the exponential proliferation phase or at the
beginning of the stationary phase (day 3 for the 5 C cultures, 36 h
for the 10 C cultures, and 20 h for the 20 C cultures) is shown in
Fig. 4. In general, higher temperatures favored the expression of
hdcA, whereas lower pH values favored the expression of the hdcA
gene (at all temperatures).