FIG. 3.

Effects of heat and osmotic pretreatments on the thermotolerance of L. delbrueckii subsp. bulgaricus strains 546, V5221, and V5242. Exponential-phase cells were centrifuged, resuspended in MPL medium, and incubated for 10 min at 65°C without pretreatment (black columns), after treatment at 50°C for 30 min (white columns), or after treatment for 30 min with 0.4 mol of NaCl/liter (gray columns). Each point is the average of at least five independent experiments. Standard deviations are shown by bars.