Interactions of de novo designed peptides with bacterial membranes: Implications in the resulted antimicrobial activity

MATURANA, P.; MARTINEZ, M.; ESPECHE J.; MAFFIA, P.C.; HOLLMANN, A

La Plata, Buenos Aires

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofisica (SAB)

Antimicrobial peptides (AMPs) are small cationic molecules that display antimicrobial activity against a wide range of bacteria, fungi and viruses. In a previous work by using model membranes we studied two related novel peptides, P6 that no show antimicrobial activity and P6.2 witch exhibited good antibacterial. However, beside biophysical techniques on model membranes can provide very detailed information on the interaction of AMPs with membranes, until recently, it was unknown if any of the information predicted was relevant for AMPs activity in real bacteria. In this context, in the present work we evaluated by using Zeta Potential, Absorbance and fluorescent approaches the effect of both peptides in bacteria. First, Zeta Potential, using as a bacterial model Escherichia coli (gram -) and Staphylococcus aureus (Gram +), was applied. The obtained results confirming that both peptides were able to interact with negative bacterial envelop. However, the effects on P6.2 were much more noticeable in both bacterial models. In order to get an insight in the effect that both peptides induce in the bacterial membrane, the disruption of outer (OM) and inner (IM) membrane of E. coli was analyzed. For study OM permeabilization the probe 1-Nphenylnaphthylamine (NPN) only able to insert in previously damage OM was used. Beside both peptides were able to damage the OM, 5 times concentration of inactive P6 was needed in order to obtain comparable results that those obtained with P6.2. Also the kinetic exhibited by P6.2 was much faster than 6. Finally, IM disruption was assed following the coloured product of cytosolic -galactosidase. As expected, P6.2 not only exhibits more product formation, implying a greater disruption of the membrane but a faster kinetic.All data put together, allows postulating, in more physiologic model, where the lower affinity of P6 for bacterial envelope results in minor final concentration of the peptide in the bacterial membrane unable to trigger the antimicrobial activity.