Exploring Antimicrobial Peptides Efficacy against Fire Blight (Erwinia amylovora)

Antimicrobial peptides (AMPs) are a various group of molecules found in a wide range of organisms and act as a defense mechanism against different kinds of infectious pathogens (bacteria, viruses, and fungi, etc.). This study explored the antibacterial activity of nine candidates reported in the literature for their effect on human and animal bacteria, (i.e., Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) against Erwinia amylovora (E. amylovora), the causal agent of fire blight disease on pome fruits. The antibacterial activity of these peptides against E. amylovora was evaluated in vitro using viable-quantitative PCR (v-qPCR), fluorescence microscopy (FM), optical density (OD), and transmission electron microscopy (TEM), while the in vivo control efficacy was evaluated in treating experimental fire blight on pear fruits. With a view to their safe and ecofriendly field use in the future, the study also used animal and plant eukaryotic cells to evaluate the possible toxicity of these AMPs. Results in vitro showed that KL29 was the most potent peptide in inhibiting E. amylovora cell proliferation. In addition, the results of v-qPCR, FM, and TEM showed that KL29 has a bifunctional mechanism of action (lytic and non-lytic) when used at different concentrations against E. amylovora. KL29 reduced fire blight symptoms by 85% when applied experimentally in vivo. Furthermore, it had no impact on animal or plant cells, thus demonstrating its potential for safe use as an antibacterial agent. This study sheds light on a new and potent antibacterial peptide for E. amylovora and its modes of action, which could be exploited to develop sustainable treatments for fire blight.