Figure 6. Effect of the stabilized MetA on the persister cell frequency under acidic conditions.

Cultures of WE and WE-LYD grown for 16 h in M9 glucose medium (pH 6.0) at 37°C with or without sodium acetate (20 mM; A); with or without L-methionine (50 µg/ml) and in the presence of sodium acetate (20 mM; B) were diluted in fresh M9 glucose medium to an OD₆₀₀ of 0.1, supplemented with ampicillin and incubated at 37°C for 10 hours. Samples were analyzed as described in the Materials and Methods. Soluble and insoluble protein fractions were purified from the 16 h-cultures grown in M9 glucose medium (pH 6.0) with or without sodium acetate (20 mM), and subjected to 12% SDS-PAGE, followed by Western blotting using rabbit anti-MetA antibody (C). The MetA in the samples was quantified through densitometry using WCIF ImageJ software. The amount of MetA in the WE cells grown without sodium acetate was set to 1 (D). The data are presented as the average of two independent experiments.