4.2.4 Transfection of bacteria.
FAM-labeled S1 was used for the preparation of fluorescently labeled Td. Bacteria (1×106 CFU/mL) were incubated with 0.1, 0.5, or 1 μM FAM-Td in PBS and then treated with 500 U/mL DNase for 15 min. FAM-S1 was used as a control. To optimize the transfection conditions, LP2000 was mixed with Td at ratios of 0.0025, 0.0125, 0.025, and 0.125 μL/μg before incubating with bacteria, and the optimum ratio (0.125 μL/μg) was used in subsequent experiments.