FIG 5.

Quantitation of MB associated with PDI-tolerant cell pellets. Cultures of naive bacteria, bacteria exposed to seven sequential daily MB+L+ treatments, and bacteria exposed to seven sequential daily MB+L− treatments were treated with 12.5 μg/ml (33 μM) MB at room temperature for 30 min. After incubation, cells were pelleted and aliquots of the supernatant were saved for MB quantification. Cell pellets were resuspended in an equal volume of PBS. MB was quantitated for both the cell pellet-associated suspension (A) and supernatant (B) using an absorption reading measured spectrophotometrically. Data were collected from 3 independent experiments performed in duplicate. Error bars represent SD. Statistical differences were determined by an unpaired, two-tailed Student's t test. *, P < 0.03; **, P < 0.002; ***, P < 0.0004; ns, not significant.