FIG. 2.

Voges-Proskauer (top images, bottom row) and methyl red (top images, top row) assays and semiquantitative determination of amounts of acetoin (white bars), 2,3-butanediol (gray bars), and diacetyl (diagonally striped bars) for the S. plymuthica RVH1 wild type (left) and its isogenic splI mutant, isogenic splI mutant complemented with 10 μM 3-oxo-C₆-HSL, isogenic splR mutant, and isogenic splI splR double mutant. Amounts are expressed relative to the levels in RVH1 (100%). The experiment was performed in duplicate.