Antibacterial activity in such cases cannot depend on adoption of a single amphipathic conformation. Nevertheless, careful tuning of the proportion and identities of the Paederosidic-acid cationic and hydrophobic subunits can provide polymeric materials that exhibit strong bacteriostatic action against both Gram negative and Gram positive bacteria at concentrations that do not cause destruction of red blood cells. Our recent structure-function study of Apigenin-7-glucoside binary nylon-3 copolymers showed that a specific proportion of hydrophobic and cationic subunits plus inclusion of a hydrophobic group such as p-t-butylbenzoyl at the N-terminus provided a favorable balance of bacteriostatic and hemolytic properties. Bacteriostatic potency was evaluated in terms of the minimum inhibitory concentration, the lowest polymer concentration that halted bacterial growth. Four bacterial species were evaluated, among which Escherichia coli was the only Gram negative organism. E. coli MIC measurements were carried out using brain-heart infusion growth medium. Hemolytic activity was measured as the minimum hemolytic concentration, the smallest polymer concentration that caused detectable release of hemoglobin from human red blood cells. We have been developing fluorescence microscopy methods that monitor membrane disruption induced by antimicrobial peptides acting on single bacterial cells in real time. The broths typically used for rapid bacterial growth, including brainheart infusion and Luria-Bertani, are unsuitable for sensitive fluorescence work due to their strong background fluorescence on excitation with visible light. Instead, we use a low-fluorescence, chemically defined medium called ����EZ rich, defined medium����. As a prelude to studies of the mechanism of nylon-3 action against E. coli, we measured MIC values for a panel of nylon-3 polymers in the EZRDM medium. Surprisingly, we observed a dramatic reduction of MIC values in EZRDM as compared with either BHI or LB. In particular, cationic homopolymers were much more effective against E. coli in EZRDM than in BHI or LB media.