FIG 1.

“Ringless” transposon mutant strains have acid-sensitive phenotypes. Stationary-phase cultures were grown in BHI medium at 37°C before being challenged in acidified BHI medium (pH 2.5) at 37°C. At 0, 30, 50, and 120 min, samples were taken for viable count measurements. The dotted line represents the detection threshold. Each marker represents the measurement average from three independent biological replicates performed, with the respective standard deviations. Statistical analysis was performed using a paired Student t test (***, P value of <0.001).