Fig. 1.

HTS assay for inhibitors of bacterial motility. (A) Dose-response evaluation of phenamil (■) and tetracycline (▴) for motility inhibition in 384-well plates, measured by the OD₆₁₅. (B) Dose-response evaluation of phenamil (■) and tetracycline (▴) for toxicity in 384-well plates, measured with alamarBlue. In each case, the data are expressed as percent inhibition relative to the OD₆₁₅ reading or alamarBlue fluorescence signal in the absence of compound. (C) Sample plate. Plates were inoculated with the motile strain C7258. Columns 1 and 2 contained phenamil (rows 1 to 4) or tetracycline (rows 5 to 16). Compounds that specifically inhibit motility (phenamil-like) without affecting viability can be distinguished from those with bactericidal activity (Tet-like) in this plate. Compounds such as phenamil, which inhibits motility but not viability, yield a bright (pink) alamarBlue fluorescence signal (column 8, row 5); compounds that do not affect motility or viability yield a blurred alamarBlue signal due to bacterial spreading across the well; and bactericidal compounds yield a Tet-like (blue) alamarBlue signal (column 8, row 3).