Correlation between the level of Alr and the level of d-cycloserine resistance in L. lactis. PH3960 harboring pGIP013 was cultured with different concentrations of nisin and d-cycloserine. After 2 h, the growth rate was determined by OD600 measurement. Cultures were induced with 0, 0.01, 0.1, or 1 ng of nisin per ml (black, gray, hatched, and white bars, respectively). Note that growth without d-cycloserine was similar for all nisin concentrations and is taken as 100%.