Browsing by Author "Semorile, L."
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- Lipid selectivity in novel antimicrobial peptides : implication on antimicrobial and hemolytic activityPublication . Maturana, P.; Martinez, M.; Noguera, M. E.; Santos, N. C.; Disalvo, E. A.; Semorile, L.; Maffia, P. C.; Hollmann, A.Antimicrobial peptides (AMPs) are small cationic molecules that display antimicrobial activity against awide range of bacteria, fungi and viruses. For an AMP to be considered as a therapeutic option, it musthave not only potent antibacterial properties but also low hemolytic and cytotoxic activities [1]. Eventhough many studies have been conducted in order to correlate the antimicrobial activity with affinitytoward model lipid membranes, the use of these membranes to explain cytotoxic effects (especiallyhemolysis) has been less explored. In this context, we studied lipid selectivity in two related novel AMPs,peptide 6 (P6) and peptide 6.2 (P6.2). Each peptide was designed from a previously reported AMP, andspecific amino acid replacements were performed in an attempt to shift their hydrophobic momentor net charge. P6 showed no antimicrobial activity and high hemolytic activity, and P6.2 exhibited goodantibacterial and low hemolytic activity. Using both peptides as a model we correlated the affinity towardmembranes of different lipid composition and the antimicrobial and hemolytic activities. Our results fromsurface pressure and zeta potential assays showed that P6.2 exhibited a higher affinity and faster bindingkinetic toward PG-containing membranes, while P6 showed this behavior for pure PC membranes. Thefinal position and structure of P6.2 into the membrane showed an alpha-helix conversion, resulting in aparallel alignment with the Trps inserted into the membrane. On the other hand, the inability of P6 toadopt an amphipathic structure, plus its lower affinity toward PG-containing membranes seem to explainits poor antimicrobial activity. Regarding erythrocyte interactions, P6 showed the highest affinity towarderythrocyte membranes, resulting in an increased hemolytic activity. Overall, our data led us to concludethat affinity toward negatively charged lipids instead of zwitterionic ones seems to be a key factor thatdrives from hemolytic to antimicrobial activity.
- Study of surface damage on cell envelope assessed by AFM and flow cytometry of Lactobacillus plantarum exposed to ethanol and dehydrationPublication . Bravo-Ferrada, B. M.; Gonçalves, S.; Semorile, L.; Santos, N. C.; Tymczyszyn, E. E.; Hollmann, A.Aims: In this work, we evaluated freeze-drying damage at the surface level of oenological strain Lactobacillus plantarum UNQLp155, as well as its ability to grow in a synthetic wine with and without pre-acclimation. Methods and Results: Damage on cell surface was studied by flow cytometry, zeta potential and atomic force microscopy, and cell survival was analysed by plate count. Results showed that beside cells acclimated at lower ethanol concentration (6% v/v) became more susceptible to drying than nonacclimated ones, after rehydration they maintain their increased ability to grow in a synthetic wine. Acclimation at a higher ethanol concentration (10% v/v) produces several damages on the cell surface losing its ability to grow in a synthetic wine. Conclusions: In this work, we showed for the first time that sublethal alterations on bacterial surface induced by a pre-acclimation with a low ethanol concentration (6%), upon a freeze-drying process, result in a better bacterial adaptation to the stress conditions of wine-like medium, as well as to the preservation process. Significance and Impact of the Study: Understanding the adaptation to ethanol of oenological strains and their effects on the preservation process has a strong impact on winemaking process and allows to define the most appropriate conditions to obtain malolactic starters cultures.