Fig. 5. Effects of 3-mercaptopropionic acid and aminooxyacetic acid on the survival of E. coli under extremely acidic conditions.E. coli wild-type and mutant strains were cultivated in pH 5.5 LBG broth for 18 h and diluted to pH 2.5 M9 minimal medium broth containing 3-mercaptopropionic acid at 500 μM (A) or aminooxyacetic acid at 5 μM (B). After 2 h incubation, bacterial viability was determined by diluting and spreading aliquots of the culture samples onto LB agar plates. Bacterial survival rate was obtained by dividing the bacterial number (CFU/ml) from pH 2.5 samples by the number (CFU/ml) from pH 5.5 samples. The survival rate of wild-type E. coli was set to 100%.