Fig 3.

Plaque-forming substances present in the supernatants of L. monocytogenes 10403S grown to stationary phase at 7°C and then exposed to acid shock (pH 3.5) for 15 min (gray bars) or not acid shocked (white bars) and incubated at 7°C or 37°C for 2 or 4 h. The solid line at 3.59 log₁₀(PFU/ml) represents the mean count at time zero (i.e., stationary-phase culture with no acid stress or subsequent incubation). Dashed lines represent the standard deviations of the counts at time zero. Instances where cultures incubated at 7°C showed significantly higher log₁₀(PFU/ml) than cultures incubated at 37°C are indicated with an asterisk (P < 0.05, matched-pairs analysis). Bars show the averages of four biological replicates; error bars represent standard deviations.