Identification and characteristics of a novel cecropin from the armyworm, Mythimna separata

Abstract

Background: The recent emergence of antibiotic-resistant strains of bacteria has increased the need to develop effective alternatives to antibiotics. Antimicrobial peptides have been considered as a promising product with several advantages. Results: In this present study, we identified a novel cecropin from the armyworm, Mythimna separata (armyworm cecropin 1, AC-1) by transcriptome sequencing and multi-sequence alignment analysis . The AC-1 precursor comprised 63 amino acid residues, containing a conserved cleavage site of the signal peptide, Ala 23 -Pro 24 , while the mature AC-1 included 39 amino acid residues. Chemically-synthesized AC-1 exhibited low hemolytic activity against chicken red blood cells, low cytotoxicity against swine testis cells, and effective antimicrobial activity against Salmonella , Escherichia coli ( E. c oli ), Klebsiella pneumonia ( K. pneumonia ), and Pseudomonas aeruginosa ( P . aeruginosa ). Its antimicrobial activity against Salmonella remained after incubation for 1 h at 100 °C or in 250 mM NaCl, KCl, and MgCl 2 solution, implying good thermal- and salt-resistant stabilities. The bactericidal effect of AC-1 on E. c oli gradually increased with the increase of AC-1 concentration, and AC-1 could cause significant deformation , severe edema, cytoplasmic lysis, cell membrane damage of E. c oli , and reduce intracellular electron density. Additionally, the fusion protein AC-1 expressed in E. coli was digested by enterokinase protease to obtain the AC-1, which showed similar antimicrobial activity against E. c oli with chemically-synthesized AC-1. Conclusions: This study identified a novel antimicrobial peptide that may represent a potential alternative to antibiotics.