RT-PCR analyses of biofilm and planktonic cells from S. mutans clinical strains. For FSC-3 and -4, we used the primers PS0941-b, PS1731, PS1365, and PS0092 to amplify the target genes described in Table 1. A control primer was used to normalize the expression of the test genes. Total bacterial RNA was isolated from biofilm and planktonic samples, and RT-PCR was performed as described in Materials and Methods. The data shown are representative of two independent assays.