Bat Cathelicidins as Natural Antimicrobial Agents: A Computational and In Vitro Investigation

Antimicrobial peptides (AMPs) are small proteins that play an important role in the innate immune system of various organisms, including plants, animals, and humans. These natural defence molecules have attracted considerable interest due to their potential as alternative antimicrobial agents to combat infectious diseases. In this study, we used computational and in vitro methods to investigate the antimicrobial activity of cathelicidin family peptides from bat species with different ecological niches.

The study of the physicochemical parameters of the peptides (hydrophobicity and net charge), together with the study of the helical regions, allowed us to deduce the antimicrobial character of peptides. To analyse the antimicrobial activity in vitro, we first determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against four different bacteria: E. coli, Salmonella, S. aureus, and E. faecalis. We then selected the most effective peptide and assessed whether it acts as a bacteriostatic or bactericidal agent. Additionally, we investigated the duration of its activity and its ability to lyse bacterial cells. We accomplished this by plotting killing curves during both the exponential and latent phases of bacterial growth. Finally, we evaluated the peptide's potential to cause hemolysis in rat erythrocytes. 10⁵

One of our peptides revealed a high antimicrobial activity, with MIC and MBC values ranging from 3.12 to 1.56 μM. It also demonstrated bactericidal properties during the stationary phase but acted as a bacteriostatic agent during the exponential phase. Notably, it exhibited lytic activity against the tested bacteria but no hemolytic activity against rat erythrocytes.