Zymographic analysis of autolytic enzyme extracts. Bacteriolytic enzyme profiles were analyzed on SDS gels (10% separation gel) containing lyophilized M. luteus cells (0.2%) or S. epidermidis cells (0.2%) as substrates. After electrophoresis, the gels were washed for 30 min in distilled water, incubated for 6 h at 37°C in a buffer containing Triton X-100, and then stained with methylene blue. The S. epidermidis atlE mutant was used as a negative control. Bands with lytic activity were observed as clear zones in the opaque gel. The clear zones appeared as dark bands after photography against a dark background. The molecular mass standard is shown on the left of the gels. Ex-Lys, cell-wall extracts of lysostaphin-treated S. epidermidis; Ex-SDS, cell-wall extracts of SDS-treated S. epidermidis; Ex-Sup, concentrated S. epidermidis culture supernatants; WT, SE1457; SAE, SE1457ΔsaeRS; SAEC, SE1457saec; ATLE, SE1457ΔatlE.