Antimicrobial peptides (AMPs) can be produced in mealworms. In this work, we integrated Bombyx mori (Bm) AMP, cecropin A to Beauveria bassiana ERL1170 by restriction enzyme-mediated integration method, which was confirmed by RT-PCR and an antibacterial activity assay. For the extracellular secretion of Bm cecropin A protein, the active domain of the cecropin A gene was tailed to the signal sequence of B. bassiana chitinase (Bbs). To exchange Bbs-cecropin A gene with egfp gene in pBARKS1-egfp, Bbs-cecropin A fragment was cut from pGEMBbs-cecropin A using XbaI/blunted and BamHI and ligated with cut pBARKS1-egfp using NcoI/blunted and BamHI, designated as pBARKS1-Bbs-cecropin A. After the transformation, transformants were grown on Czapek’s solution agar containing 600 μg ml-1PPT. Expression of Bm cecropin A was confirmed by RT-PCR. Strong clear zone was observed in the co-culture of the transformant D-6 and Bacillus subtilis on fourth strength Sabouraud dextrose agar 1 day after the culture at 25°C, whereas the wild type had no clear zone. This work suggests that Bm cecropin A can be efficiently produced in this mealworm-based fungal expression platform, thereby increasing the value of mealworms in the animal feed additive industry.

Antimicrobial peptides (AMPs) can be produced in mealworms, currently being used as animal feeds, by the infection of genetically engineered-entomopathogenic fungi. In this work, we integrated Bombyx mori (Bm) AMP, cecropin A to Beauveria bassiana ERL1170 by restriction enzyme-mediated integration method, which was confirmed by RT-PCR and an antibacterial activity assay. For the extracellular secretion of Bm cecropin A protein, the active domain of the cecropin A gene was tailed to the signal sequence of B. bassiana chitinase (Bbs). To exchange Bbs-cecropin A gene with egfp gene in pBARKS1-egfp, Bbs-cecropin A fragment was cut from pGEM-Bbs-cecropin A using XbaI/blunted and BamHI and ligated with cut pBARKS1-egfp using NcoI/blunted and BamHI, designated as pBARKS1-Bbscecropin A. After the transformation, transformants were grown on Czapek’s solution agar containing 600 μg ml-1PPT. Expression of Bm cecropin A was confirmed by RT-PCR. Strong clear zone was observed in the co-culture of the transformant D-6 and Bacillus subtilis on fourth strength Sabouraud dextrose agar 1 day after the culture at 25°C, whereas the wild type had no clear zone. This work suggests that Bm cecropin A can be efficiently produced in this mealworm-based fungal expression platform, thereby increasing the value of mealworms in the animal feed additive industry.

The antimicrobial peptide cecropin was isolated from the larval hemolymph of immune-challenged japanese oak silkworm, Antheraea yamamai. The full-length cDNA of A. yamamai cecropin (Ay-cecA) was cloned by a combination of RT-PCR and 3' RACE based on N-terminal sequence obtained by Edman degradation. The cloned cDNA consists of 419 nucleotides encoding a 64 amino acid precursor containing a 37-residue mature peptide. Like many insect cecropins, Ay-cecA also harbored a glycine residue for C-terminal amidation at the C-end. To understand this peptide better, we successfully expressed bioactive recombinant Ay-cecA in E. coli BL21(DE3) by fusing with ketosteroid isomerase (KSI) to avoid the cell death during induction. The fusion CecA-KSI protein was expressed as inclusion body at high level. Recombinant Ay-cecA was easily released by cleavage of the fusion protein with cyanogen bromide (CNBr), and purified by FPLC chromatography. The purified recombinant Ay-cecA showed considerably antibacterial activity against Gram-negative bacteria, E. coli ML 35, Klebsiella pneumonia and Pseudomonas aeruginosa. The time-kill assay showed that Ay-CecA displayed a time-dependent bactericidal activity, as was also seen after treatment with melittin. our results proved that Ay-cecA can be developed into novel antibacterial agent.

Cecropin is an antimicrobial peptide that is synthesized in fat body cells and hemocytes of insect in response to a hypodermic injury or bacterial infection. A 503 bp cDNA encoding a cecropin-like antimicrobial peptide was isolated by employing annealing control primer (ACP)-based differential display PCR and 5'-RACE from immunized Papilio xuthus larvae. The open reading frame (ORF) of isolated cDNA encoded a 63 amino acid prepropeptide with a putative 22-residue signal peptide, a 3-residue propeptide and a 38-residue mature peptide with a theoretical mass of 4060.89 Da. The deduced amino acid sequence of peptide showed significant identities with other Lepidopteran cecropins. This peptide was named as papiliocin. RT-PCR revealed that the papiliocin transcript was detected at significant level after injection with bacterial lipopolysaccharide (LPS). Based on the deduced amino acid sequence of papiliocin, a 38-mer mature peptide was chemically synthesized by Fmoc method, and analyzed antimicrobial activity. The synthetic papiliocin peptide had a broad spectrum of activity against fungi, Gram-positive and negative bacteria, and also showed no hemolytic activity against human red blood cell.