FIG 9.

Antibiotic tolerance of alginate-encapsulated P. aeruginosa PAO1. (A to C) CLSM images of nontreated control beads with P. aeruginosa grown for 24, 48, and 72 h. (D to F) CLSM images of alginate-encapsulated P. aeruginosa treated with 100 μg/ml tobramycin for 24 h. (D) P. aeruginosa exposed to tobramycin just after encapsulation (when still in single-cell planktonic state). P. aeruginosa was allowed to form aggregates for 24 h (E) or 48 h (F) before the exposure to tobramycin. Tobramycin exposure lasted for 24 h. Notice how the majority of the bacteria are green (alive) in spite of 24-h antibiotic treatment. Viability staining was with Syto9 and PI. Green bacteria are alive and red/yellow bacteria are dead. Bar, 20 μm.