Effect of subinhibitory concentrations of bile (0.1, 0.08, and 0.05%, respectively) on the transcription of putative MDR-encoding genes in B. longum subsp. longum NCC2705 (a), B. breve UCC2003 (b), and B. animalis subsp. lactis BB-12 (c) relative to the transcription of such genes in the absence of bile. The horizontal axis is placed at 1, which is the ratio reflecting the change in the expression level.