Antibacterial Activity of Juglone against Staphylococcus aureus: From Apparent to Proteomic

Abstract

The proportion of foodborne disease caused by pathogenic microorganisms is rising worldwide, with staphylococcal food poisoning being one of the main causes of this increase. Juglone is a plant-derived 1,4-naphthoquinone with confirmed antibacterial and antitumor activities. However, the specific mechanism underlying its antibacterial activity against Staphylococcus aureus remains unclear. To elucidate the mechanism underlying its antibacterial activity, isobaric tags for relative and absolute quantitation methods of quantitative proteomics were applied for analysis of the 53 proteins that were differentially expressed after treatment with juglone. Combined with verification experiments, such as detection of changes in DNA and RNA content and quantification of oxidative damage, our results suggested that juglone effectively increased the protein expression of oxidoreductase and created a peroxidative environment within the cell, significantly reducing cell wall formation and increasing membrane permeability. We hypothesize that juglone binds to DNA and reduces DNA transcription and replication directly. This is the first study to adopt a proteomic approach to investigate the antibacterial mechanism of juglone.

Keywords: Staphylococcus aureus; antibacterial activity; iTRAQ; juglone.

Figure 1

Molecular structure of juglone.

Figure 2

Indicators of damage to Staphylococcus aureus after treatment with juglone. A–C show changes in total superoxide dismutase (SOD) activity, total catalase (CAT) activity, and malondialdehyde (MDA) content, respectively; D,E show changes in DNA and RNA fluorescence intensity, detected at 364 nm and 400 nm; F shows changes in the peptidoglycan content. Error bar indicates SEM.