FIG. 5.

Comparison of the 47-kDa protease production by the parental strain and production by the mutant (E1 and CS1) strains. The different strains were grown in NB; after 24 h of incubation 20 ml of each supernatant was dialyzed, freeze-dried, and resuspended in 0.5 ml of Tris buffer (protein concentration, 50 μg/ml), and 10- to 40-μl aliquots were used to analyze the presence of the 47-kDa protein by SDS–12% PAGE (A), caseinolytic activity by zymograms by using 1% sodium caseinate (B), and the immunoblot probed with antibodies (1:500) raised against the 47-kDa protein (C). Molecular mass markers (expressed in kilodaltons) are indicated on the left. Lanes 1, parent strain (Y. ruckeri 150); lanes 2, mutant strain E1; and lanes 3, mutant strain CS1.