FIG 6.

Effect of calcium supplementation on protease activity. Qualitative analysis of protease activity of BHI supernatant samples using skim milk assays. (A) Addition of 1 mM CaCl₂ to BHI medium prior to bacterial inoculation (BHIC) restores WT protease activity in the ΔaprA mutant and increases the proteolytic activity of the ΔlasB mutant. (B) Addition of 1 mM CaCl₂ after collection of filtered supernatants (plus 1 mM CaCl₂) did not restore WT protease activity. Images shown are representative of three independent experiments.