Abstract
Antibiotic resistance is at dangerous levels and increasing worldwide. The search for new antimicrobial drugs to counteract this problem is a priority for health institutions and organizations, both globally and in individual countries. Sarconesiopsis magellanica blowfly larval excretions and secretions (ES) are an important source for isolating antimicrobial peptides (AMPs). This study aims to identify and characterize a new S. magellanica AMP. RP-HPLC was used to fractionate ES, using C18 columns, and their antimicrobial activity was evaluated. The peptide sequence of the fraction collected at 43.7 min was determined by mass spectrometry (MS). Fluorescence and electronic microscopy were used to evaluate the mechanism of action. Toxicity was tested on HeLa cells and human erythrocytes; physicochemical properties were evaluated. The molecule in the ES was characterized as sarconesin II and it showed activity against Gram-negative (Escherichia coli MG1655, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa PA14) and Gram-positive (Staphylococcus aureus ATCC 29213, Micrococcus luteus A270) bacteria. The lowest minimum inhibitory concentration obtained was 1.9 μM for M. luteus A270; the AMP had no toxicity in any cells tested here and its action in bacterial membrane and DNA was confirmed. Sarconesin II was documented as a conserved domain of the ATP synthase protein belonging to the Fli-1 superfamily. The data reported here indicated that peptides could be alternative therapeutic candidates for use in infections against Gram-negative and Gram-positive bacteria and eventually as a new resource of compounds for combating multidrug-resistant bacteria.
Highlights
Antimicrobial peptides (AMPs) are present in most forms of life, ranging from bacteria to plants, vertebrates and invertebrates [1]
The present study described the process of obtaining, characterizing and evaluating the antibacterial activity of a new antimicrobial peptides (AMPs) derived from the larval excretions and secretions (ES) of S. magellanica, named sarconesin II
The evaluation of the sarconesin II fraction’s antibacterial activity against Gram-positive and Gram-negative bacteria was demonstrated by Minimum inhibitory concentration (MIC)
Summary
Antimicrobial peptides (AMPs) are present in most forms of life, ranging from bacteria to plants, vertebrates and invertebrates [1]. They form part of insects’ complex innate immune system, conferring protection against microbial infections and are synthesized in fat bodies and in hemocytes [2,3,4]. AMPs have been identified in necrophagous flies’ salivary glands [8] and are important components of larval excretions and secretions (ES) during this phase of their biological development. Larval external digestion means that digestive enzymes such as serine and metalloproteinases, antibacterial molecules and other biochemicals produced by them are constituents of ES [9,10]. As flies live in an environment contaminated by pathogens’ oral ingestion, their innate defense system is activated, inducing
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