Abstract
Dung beetles are exposed to a complex microbiological ecosystem during their life cycle. Characterization of novel host-defense peptides (HDP) is essential to understanding the host innate immune response in insects. It constitutes a promising alternative to look for new therapeutic agents against pathogenic microbes. We identified four new HDP, Oxysterlins 1, 2, 3, and 4 from the transcriptome of the Oxysternon conspicillatum dung beetle. These HDP display a highly conserved signal peptide and a mature peptide, characterized by an overall positive charge (cationic) (pI: 10.23–11.49), a hydrophobic ratio (ΦH: 35–41), and amphipathicity. Oxysterlins 1, 2, and 3 have a linear α-helix structure, whilst Oxysterlin 4 has a mixture of both α-helix and β-sheet structures without disulfide bonds through bioinformatics prediction and circular dichroism. Oxysterlins are part of the cecropin family group in an exclusive clade related to beetle cecropins. They have predominant antimicrobial activity against Gram-negative bacteria, including multidrug resistant strains (3.12–50 μg/mL) measured by plate microdilution. Their kinetics, in a time-killing curve showed concentration-dependent bactericidal activity. Furthermore, these HDP have low toxicity against human erythrocytes (62.5–500 μg/mL) and Vero cells (250–500 μg/mL). This article describes new HDP of the cecropin family from the Oxysternon conspicillatum dung beetle, with antimicrobial activity against multidrug resistant bacteria and low toxicity.
Highlights
There is an urgent need to search for new antimicrobial agents; indiscriminate use of antibiotic therapy, as well as decreased research and development of new active antibiotics against resistant organisms are leading to a public health crisis [1]
A total of 200 mg of fat body was extracted per beetle and 10.1 μg of total RNA at 380.1 ng/μL were obtained with an RNA integration number of 7.9 for transcriptome sequencing
We used the Trinity platform software to perform a paired-end joining de novo assembly of the valid reads, 27,603 contigs were obtained with a read length from 201 to 12,138 bp and an N50 of 2,159 bp with version: GEXM00000000.1 and code TSA: GEXM01000001-GEXM01027567 in the NCBI GenBank
Summary
There is an urgent need to search for new antimicrobial agents; indiscriminate use of antibiotic therapy, as well as decreased research and development of new active antibiotics against resistant organisms are leading to a public health crisis [1]. The emergence of resistance to last-resort drugs, like third-generation cephalosporins, is fast outpacing the development of alternative treatments and will influence on the burden of disease, like E. coli (ESBL and fluoroquinoloneresistant), which is a growing global concern with a reported two-fold increase in all-cause
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