Effect of divalent cations and EDTA as modulators of P128 activity. 2 μg of P128 (10 μg/ml) was pre-incubated at 37°C for 30 min in concentrations of upto 50 mM of CaCl2 or MgCl2; 5 mM Zinc Acetate; 20 mM K2 EDTA before being tested on S. aureus cells. The final concentrations in the assay were 25 mM of CaCl2 or MgCl2; 2.5 mM Zinc Acetate; 10 mM K2 EDTA. P128 was lethal to S. aureus cells in the presence of millimolar concentrations of EDTA or divalent cations; Ca2+, Mg2+ and Zn2+. This was evaluated in duplicates and the experiment performed thrice. Results are expressed as mean residual CFU/ml±standard deviation.