FIG. 5.
Overproduction of mutated Dam decreases Act antigen levels and protease activities to those of the WT A. hydrophila strain. (A) Production of Act based on ELISA with the culture supernatants of the A. hydrophila strain with pBAD vector only, the pBAD/damAhSSU recombinant plasmid, and the pBAD/damD/A or the pBAD/damY/A plasmid. (B) Protease activity in the culture supernatants of A. hydrophila strains with pBAD, pBAD/damAhSSU, pBAD/damD/A, or pBAD/damY/A plasmid, as measured by the hydrolysis of Hide azure powder. The strains were grown in LB medium with arabinose. Three independent experiments were performed, and the arithmetic means ± standard deviations were plotted. The data were normalized to 1 × 108 CFU to account for any differences in the growth rates of the various bacterial strains used. Asterisks denote statistically significant values by Student's t test.