Transcription of gtfB/gtfC from S. mutans following HDA treatment. gtfB/gtfC expression is completely abrogated by exposure to HDA. gtfB/gtfC levels are also reduced with lower concentrations of HDA. The error bars represent mean and standard deviations of experiments performed in triplicate. gtf genes were more abundantly expressed in cultures that treated with 0.0, 100 and 200 μg ml-1 of HDA but missing in the cells treated with 1000 μg ml-1 of HDA.