FIG. 3.

Influence of respiration on bactericidal activity of lactoferrin. (A) Viability of P. aeruginosa cells (10⁶ cells/ml) incubated for 90 min at 37°C with 1 μM rhLf or 4 μM transferrin during aerobiosis and anaerobiosis. (B and C) Experimental conditions were the same as those described for panel A, except that the assays were performed aerobically in the presence of the following respiration inhibitors and uncouplers: 1 mM azide (lightest gray bars), 10 μM antimycin (light gray bars), 50 μM CCCP (dark gray bars), and 32 μM piericidin A (darkest gray bars). The activities of different concentrations of rhLf (black bars) and hTf (white bars) alone were also tested. (D) Consumption of oxygen in P. aeruginosa resting cells (○) or cells incubated with 3 μM rhLf (▪), 12 μM hTf (▵), or 32 μM piericidin A (▾), as a positive control, added 15 min before the O₂ consumption measurement. (E) Viability of P. aeruginosa cells treated with rhLf (▪) or hTf (▵) in the presence of different concentrations of the electron acceptor DCIP under anaerobic conditions. (F) Concentration of oxidized DCIP in control cell suspensions (○), after addition of 3 μM rhLf (▪) or 12 μM hTf (▵), and in the presence of 3 μM rhLf (▾) or 12 μM hTf (⧫) without cells. *, P < 0.05 versus untreated controls.