FIG. 4.
PlyC activity in the presence of additives/contaminants. PlyC (0.2 μg) was tested in the spectrophotometric lysis assay against S. equi 9528 (Smr) in the presence of 1% detergent (SDS [anionic], CTAB [cationic], CHAPS [zwitterionic], Triton X-100, Tween-20, and Brij 35 [all nonionic]), 10 mM EDTA, distilled water, 10% organic load (fetal bovine serum), or synthetic hard water (SHW). Error bars show standard deviation of triplicates. **, 400 ppm of SHW caused clumping of bacterial cells and erroneous optical density readings (see text); ##, 800 ppm of SHW was tested by the plate viability assay for this figure, and percent lysis of the control was calculated from controls subjected to the plate viability assay (data not shown).