Time course for growth of L. plantarum WCFS1 carrying pEH9R or pEH9A. Cultivations were carried out with pH control at pH 6.5 in 400-ml laboratory fermentors at 37°C using MRS medium (40 g/l glucose). The graph shows OD600 (solid lines), β-galactosidase activity (units per milliliter of fermentation broth) (dashed lines) and specific activity (units per milligram protein) (dotted lines). Cultures were induced with 80 ng/ml of pheromone after six hours of growth, i.e. at an OD600 of approximately 3.0.