FIG. 7.

Densitometric analysis of MetA proteins in heat (A, B)-stressed and acetic acid (C, D)-stressed cultures. Strains WE (white columns), 333 (gray columns), D267 (dark gray columns), and T229 (black columns) were grown in M9 glucose medium to exponential phase (OD₆₀₀ = approximately 0.6) at 30°C and then shifted to 45°C for 40 min or incubated in the presence of 30 mM acetic acid for 3 h at 30°C. Soluble (A, C) and aggregated (B, D) fractions of MetA proteins were purified from 25-ml cultures as described in Materials and Methods. Three micrograms of total protein was subjected to 12% SDS-PAGE, followed by Western blotting with rabbit anti-MetA serum. MetA proteins were quantified by densitometry with LabWorks software and normalized to the total amount of protein. MetA proteins from the unstressed cultures were made equal to 1 (plain columns). An average of two independent experiments is presented.