Fig 6.

ilvE promoter activity is downregulated by bcAAs and induced under nutrient-limiting conditions. CAT activity was determined for S. mutans UR213 (ilvE promoter-cat fusion in the UA159 parent strain) grown in BHI medium (A) or FMC minimal medium (B) supplemented with bcAAs. Transcriptional activity was determined as described in Materials and Methods. The growth medium was supplemented with the branched-chain amino acid isoleucine (I) or leucine (L), to a final concentration of 1 mM. Statistical significance was determined by Student's t test. *, P ≤ 0.00001 (n = 3). Pairwise comparisons are represented by lowercase letters. n.s., not statistically significant.