FIG 4.

Secreted protease activity from strain PIC3611 with induced expression of putative metalloprotease genes. (A to C) Induction of His₇-tagged putative metalloprotease genes from a p15a-based plasmid in strain PIC3611 was followed by measuring protease activity and cytotoxic capacity in the filtered supernatants from cultures grown overnight. The negative-control was episomal plasmid pMQ125 (vector). Means and standard deviations are shown, and the asterisks indicate a significant difference from the vector control by ANOVA with Tukey's posttest (n = 6). (A) Protease production measured with azocasein. (B) Cytotoxicity to A549 airway cell line measured with Presto blue. (C) Cytotoxicity to HCLE cell line measured with Presto blue.