In this paper, we describe a rapid flow cytometry method to identify antimicrobial peptides that are
internalized into bacterial cells and differentiate them from those that are membrane active. The method was
applied to fluorescently labeled Bac71-35 and polymyxin B, whose mechanisms of action are, respectively, based
on cell penetration and on membrane binding and permeabilization. Identification of peptides with the former
mechanism is of considerable interest for the intracellular delivery of membrane-impermeant drugs.
