Bioluminescence response of RM4440 to increasing doses of UV C in biofilm. (A) Total bioluminescence (nanoamperes). (B) Normalized bioluminescence (nanoamperes per CFU per milliliter). UV C doses (J/m2): ■, 0; ●, 2.5; ▴, 5; ⧫, 10; □, 12.5; ○, 15; ▵, 17.5; ◊, 20. Each point represents the mean of three independent experiments.