Fig 2. The role of CreBC in the secreted protease activity.

Forty microliters of bacterial cell suspension was dipped onto LB agar containing 1% skim milk. After incubation at 37°C for 72 hour, the proteolytic activity of bacteria was assessed by measuring the transparent zones around the bacteria. Data represent the means from 3 independent experiments. Error bars represent the standard deviations for three triplicate samples. *, p < 0.05; ***, p < 0.001. (A) The secreted protease activities of creB, creC, and creBC mutants. (B) The secreted protease activities of creBC mutant and its derived complementation strains. Tetracycline (30 μg/ml) was added for the plasmid maintenance.