Human PGRP-S inhibits the growth of S aureus CP5 and E coli K12. (A) Radial diffusion assay. Wells were bored into underlay gel (1% agarose in 0.01 × TSB, 10 mM NaPB, pH 7.4) impregnated with bacteria. Proteins were introduced into wells (0.1-5 μg/well), and the plates were overlaid with 1% agarose in 2 × TSB (6% wt/vol) and incubated overnight at 37°C. (B) Suspension assay. Bacteria were incubated in 1 × TSB (3% wt/vol) with 25 μg/mL rhPGRP-S, either alone (•) or supplemented with 100 μg/mL S aureus PGN or E coli PGN (▴), PGN only (▦) or no additives (⋄). Tubes were shaken at 300 rpm for 5 hours, and bacterial density was monitored by measurement of optic density (OD) at 600 nm at 1-hour intervals. Data represent the mean ± SD of 3 independent experiments.