FIG. 1.

Populations of L. monocytogenes cells held at 4°C (top) or 21°C (bottom) in TPB with the pH adjusted or not adjusted with 1.0 N NaOH. Populations of alkali-injured and uninjured cells were recovered by plating cells onto TPA and TPAS, respectively. Cells were incubated in TPB at various pH values at 37°C for 45 min prior to being held at 4 or 21°C. Samples plated on TPA were taken from TPB at pHs 7.3 (■), 9.0 (●), 10.0 (▴), 11.0 (⧫), and 12.0 (░⃞), and samples plated on TPAS were taken from TPB at pHs 7.3 (□), 9.0 (○), 10.0 (▵), 11.0 (◊), and 12.0 ( ).