Finding effective antibiotics against multi-resistant strains of bacteria has been a challenging race. Linker-Evolved-Group-Optimized-Lipophosphonoxins (LEGO-LPPOs) are small modular synthetic antibacterial compounds targeting the cytoplasmic membrane. Here we focused on understanding the reasons for the variable efficacy of selected LEGO-LPPOs (LEGO-1, LEGO-2, LEGO-3, and LEGO-4) differing in hydrophobic and linker module structure and length. LEGO-1-4 permeabilized cytoplasmic membrane of Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli, LEGO-1 with the longest linker module being the most effective. Gram-positive bacteria were more sensitive to LEGO-LPPO action compared to Gram-negatives, which was manifested as a delayed membrane permeabilization, higher minimal inhibitory concentration and lower amount of LEGO-LPPO bound to the cells. Outer membrane permeability measurements and time-kill assay showed that presence of the intact outer membrane brought about reduced susceptibility of Gram-negatives. Using liposome leakage and in silico simulations, we showed that membranes with major content of phosphatidylethanolamine were more prone to LEGO-LPPO permeabilization. The proposed mechanism stems from an electrostatic repulsion between highly positively charged LEGO-1 molecules and positively charged amino groups of phosphatidylethanolamine which destabilizes the membrane. Collectively, these data suggest that LEGO-LPPO membrane activity is enhanced by presence of phosphatidylethanolamine but hindered by presence of intact outer membrane.

Department of Analytical Chemistry Faculty of Science Charles University Hlavova 8 128 00 Prague Czech Republic

Department of Genetics and Microbiology Faculty of Science Charles University Viničná 5 128 00 Prague Czech Republic

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences v v i Flemingovo náměstí 2 166 10 Prague 6 Czech Republic

J Heyrovský Institute of Physical Chemistry Czech Academy of Sciences v v i Dolejškova 3 182 23 Prague Czech Republic

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