To determine whether LeuO is the casA activator in N-minimal-medium , the pKK-375 fusion was introduced into the IMSS-1 leuO strain : we found that LeuO does not induce casA expression in N-minimal-medium , since the activity values in the leuO-deficient strain were the same as those in the wild-type strain -LRB- data not shown -RRB- .