FIG. 3.

Environmental chloride reduces protease activity. Protease activity present in culture supernatants was measured after 10 h using an assay based on the cleavage of fluorescein isothiocyanate-labeled casein. Media included unmodified C medium (“0” in panel A; “None” in panel B) and C medium supplemented as indicated. Activity is presented as a percentage of the protease activity produced by HSC5 in unmodified C medium. Data represent the means and standard deviations from three independent experiments for samples analyzed in triplicate. Statistically significant differences from unmodified medium are indicated by an asterisk (P < 0.001).