Figure 2. AcmD contributes to cell autolysis.

Determination of cell lysis upon induced expression of AcmD. Cultures of L. lactis NZ9000 (pNGacmD) or L. lactis NZ9000acmA∆1 (pNGacmD) were grown until an OD₆₀₀ of 0.6 was reached. Both cultures were split in two. Expression of AcmD was induced in one half of each culture by the addition of nisin (10 ng/ml), the other halves were left un-induced. The cells of the four cultures were collected after 2 h and mixed with the cell-free culture supernatant of L. lactis MG1363 (dark grey bars) or L. lactis MG1363acmA∆1 (grey bars). After 1 h incubation at 30° C, supernatants were analyzed for PepX activity (in arbitrary units (AU)). The slope of the substrate hydrolysis/color development was determined and is indicated as PepX activity (AU)/min. The average was calculated from two independent experiments.