FIG 1.

Hemolytic activity at pH 5.5. The indicated strains were grown at 37°C to an OD₆₀₀ of 0.9 in pH-adjusted BHI (pH 5.5) before the supernatant was removed. Filtered supernatants were added at a 1:1 ratio to a 10% suspension of red blood cells, followed by incubation for 3 h at 37°C. The absorbance was measured at 541 nm. The figure shows the hemolytic activity of the indicated strains in percentages relative to the wild type (100%) with the standard deviations. All samples were compared to the wild type using a two-tailed Student t test (**, P < 0.01; ***, P < 0.001).