Biophysical Society Thematic Meeting| Lima 2019

Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level

Poster Abstracts

33-POS Board 33 UNRAVEL THE WAY OF ACTION DE NOVO DESIGNED PEPTIDES IN GRAM POSITIVE AND GRAM NEGATIVE BACTERIA Patricia del Valle Maturana 1 ; Melina Martinez 2 ; Juan Espeche 1 ; Paulo Maffia 2 ; Axel Hollmann 1 ; 1 Centro de investigaciones en biofísica aplicada y alimentos (CIBAAL)-UNSE-CONICET, Santiago del Estero, Argentina 2 Laboratorio de Microbiología Molecular, Instituto de Microbiología Básica y Aplicada (IMBA)- UNQ-CONICET, Quilmes, Argentina Antimicrobial peptides are small molecules that display antimicrobial activity against a wide range of pathogens. In previous work, by using model membranes we studied Peptide 6 that show no antimicrobial activity and Peptide 6.2 which exhibited antibacterial activity. In the present work, we aimed to unravel the way of action of theses peptide by studying its interaction with bacteria using Escherichia coli and Staphylococcus aureus.Zeta Potential experiments showed that both peptides were able to interact with a bacterial envelope. However, the effects on P6.2 were much more noticeable in both bacteria. Interesting, besides the CIM obtained for P6.2 were similar on both bacteria, the affinity seems to be higher in the case of E.coli.The ability of both peptides to disrupt the bacterial membrane was also studied. In the case of E.coli, besides both peptides were able to damage the outer membrane (OM), 5 times concentration of P6 was needed in order to obtain comparable results than those obtained with P6.2. Also, P6.2 exhibited faster kinetics of damage. The same behavior was obtained when internal membrane disruption was evaluated. When permeabilization of the cytoplasmic membrane of S.aureus was evaluated, again P6.2 exhibit higher and faster damage. When results were compared in both bacteria, E.coli showed faster kinetics and a lower amount of peptide to obtain the full permeabilization. Those results could be explained due to the OM in E.coli its higher exposure to the media whereas in S.aureus peptides requires pass through peptidoglycan to reach the cytoplasmic membrane. Also, these difference could explain the differences observed in Zeta potential. All data put together allows postulating, in a physiologic model, that the lower affinity of P6 for bacterial envelope results in a minor final concentration of the peptide in the bacterial membrane unable to trigger the antimicrobial activity.

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