Abstract
Antibiotics are commonly used to treat pathogenic bacteria, but their prolonged use contributes to the development and spread of drug-resistant microorganisms raising the challenge to find new alternative drugs. Antimicrobial peptides (AMPs) are small/medium molecules ranging 10–60 residues synthesized by all living organisms and playing important roles in the defense systems. These features, together with the inability of microorganisms to develop resistance against the majority of AMPs, suggest that these molecules might represent effective alternatives to classical antibiotics. Because of their high biodiversity, with over one million described species, and their ability to live in hostile environments, insects represent the largest source of these molecules. However, production of insect AMPs in native forms is challenging. In this work we investigate a defensin-like antimicrobial peptide identified in the Hermetia illucens insect through a combination of transcriptomics and bioinformatics approaches. The C-15867 AMP was produced by recombinant DNA technology as a glutathione S-transferase (GST) fusion peptide and purified by affinity chromatography. The free peptide was then obtained by thrombin proteolysis and structurally characterized by mass spectrometry and circular dichroism analyses. The antibacterial activity of the C-15867 peptide was evaluated in vivo by determination of the minimum inhibitory concentration (MIC). Finally, crystal violet assays and SEM analyses suggested disruption of the cell membrane architecture and pore formation with leaking of cytosolic material.
Highlights
The high increase in multidrug-resistant microorganisms is raising the challenge to find new molecules as an alternative to current antibiotics
In this work we investigate a defensin-like antimicrobial peptide identified in the Hermetia illucens insect through a combination of transcriptomics and bioinformatics approaches
This sequence was analyzed with the BLAST software accessed on 26 November 2021 showing a similarity with other antimicrobial peptides belonging to the defensins family sharing more than 50% homology with Defensin-like Peptide 4 (DLP4) from H. illucens, Aedes
Summary
The high increase in multidrug-resistant microorganisms is raising the challenge to find new molecules as an alternative to current antibiotics. Cationic peptides with a positive net charge due to the presence of basic residues (lysine and arginine) are the most widespread in nature [8]. For their high biodiversity, with over one million described species, insects represent the largest class of organisms, with a high ability to adapt to environmental changes and high resistance to a broad spectrum of pathogens [9,10]. The dipteran Hermetia illucens, is considered an excellent model system for the identification and characterization of new AMPs since it is able to live in hostile environments rich in pathogens. H. illucens is a scavenger insect, well known for its ability to bioconvert decaying substrates [15] and considered of scientific and economic interest in bioconversion processes, in animal feed and as an innovative and sustainable source of chitin, chitosan and lipids [16,17,18]
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