Figure 3. Ga inhibits growth of biofilm-forming cells, stimulates detachment, and its activity is enhanced by lactoferrin.

(A–B) The dividing time (A) and detachment rate (B) of attached bacteria were increased by 1 μM Ga(NO₃)₃. Time-lapse images of GFP-labeled P. aeruginosa in biofilm reactors from 4 separate experiments were collected in the presence and absence of 1 μM Ga(NO₃)₃. Dividing times of attached bacteria were measured by counting the number of frames between 50 cell divisions. The percentage of daughter cells detaching from the surface was determined by observing 100 daughter cells and averaging the results; *P < 0.001 versus the untreated control. (C) Ga potentiates the growth-inhibitory effects of lactoferrin. 10⁴ planktonic P. aeruginosa were inoculated in biofilm medium with various concentrations of lactoferrin alone or lactoferrin mixed with Fe or Ga. Cultures were then grown for 24 hours, and the OD₆₀₀ was measured. Fe (1 μM) blocked the growth-inhibitory effects of lactoferrin, but Ga potentiated it. Results are the mean of 3 separate experiments; error bars are SEM; *P < 0.001 versus the untreated control. (D) Ga potentiates the antibiofilm effects of lactoferrin. Confocal microscopic images of GFP-labeled P. aeruginosa grown in flow cells with biofilm medium alone and medium containing lactoferrin (20 μg/ml) or lactoferrin (20 μg/ml) plus Ga(NO₃)₃ (1 μM). Images are top views (x-y plane) obtained after 5 days of growth; scale bar: 50 μm. Results are representative of 3 separate experiments. See Supplemental Figure 3 for counts of attached bacteria.