FIG. 1.

Quantitative enzymatic assay of secreted (supernatant), cell associated, and total proteolytic and PLC activities of B. pseudomallei 1026b (□), DD213 (■), and C21 (▨). Bacterial strains were grown in Luria-Bertani broth for 24 h at 37°C with shaking (250 rpm). (A) Protease assay (11). Numerical values are presented as protease units per milliliter of culture. One unit of protease is the amount of enzyme which yields an increase in absorbance (at 595 nm) of 0.25/h at 37°C. (B) PLC assay (5). Nitrophenylphosphorylcholine hydrolysis by PLC was monitored spectrophotometrically by the measurement of p-nitrophenol at 410 nm. Total enzymatic activity is the sum of the secreted and cell-associated activities. All numerical values are the means of three separate experiments performed in triplicate plus standard deviations (error bars).