Bacterial terminal oxidase bo3 as a primary respiratory target of cathelicidin peptide hc-cath against Acinetobacter baumannii.

INTRODUCTION

Antimicrobial peptides (AMPs) hold promises to counter antimicrobial resistance. They cause several deleterious effects in bacterial cells by interfering with cell wall biosynthesis, DNA replication, transcription, and translation.

OBJECTIVES

The essential role of cellular respiration in bacterial survival underscores its potential as a target for antimicrobial intervention. However, few studies have explored if and how AMPs target bacterial respiratory terminal oxidases, which contribute to proton motive force (PMF) for ATP synthesis and are essential for cell survival.

METHODS

In vitro and in vivo experiments are performed to examine the antimicrobial activities of hc-cath, the first sea snake-derived cathelicidin peptide, against A. baumannii. Mode of action (MOA) of hc-cath is confirmed through a series of biochemical, enzymatic, and biophysical assays along with transcriptome analysis.

RESULTS

In this investigation, hc-cath is found to interact with and inhibit the terminal oxidase bo3 in A. baumannii, disrupting PMF and inducing toxic reactive oxygen species (ROS) production. Mitigating oxidative stress rescues bacterial death induced by hc-cath. Phenotypic validation using a cyoB (encoding oxidase bo3)-deficient strain further confirms the reduced peptide susceptibility and attenuates respiratory metabolic perturbation.

CONCLUSION

Our research identifies oxidase bo3, which predominates under high aeration growth conditions, as a key potential target of AMPs, underscoring bacterial respiratory metabolism as a viable therapeutic focus for AMPs-based strategies.