FIG. 2.

Effect of transferrins on the cytoplasmic membrane. (A) P. aeruginosa and L. lactis cells were incubated with or without (control) 1 μM lactoferrin (rhLf), 0.125 μM transferrin (hTf), or 50 μM Lfpep (positive control) and then stained with 1 μg/ml propidium iodide (PI). (B) Effect of transferrins on Δψ of L. lactis cells. The addition of glucose to cell suspensions (10⁷ cells/ml) resulted in the generation of a membrane potential, observed as a decrease in DiSC₃(5) fluorescence, in control assays (control). Cells were preincubated (30 min, 30°C) with 2 μM lactoferrin (rhLf), 20 μM transferrin (hTf), or 1 mM DCCD. Additions of glucose and 2 μM valinomycin (Val) are indicated (arrows). Fluorescence is expressed in arbitrary units (A.U.).