Cell wall disruption, membrane damage, and decrease in the expression of Yrp1 virulence factor in Yersinia ruckeri by propolis ethanol extract

Instead of antibiotics, propolis is a promising alternative for treating bacterial diseases. The aim of this study was to evaluate the effect of propolis ethanol extract (PEE) on Yersinia ruckeri (Y. ruckeri), a fish pathogen, by examining its impact on the cell wall, cytoplasmic membrane, and gene expression.

The effect of propolis on the bacterial cell wall, membrane, and DNA using scanning electron microscopy (SEM) was investigated. Its effect on the NAD+/NADH ratio, reactive oxygen species (ROS) production, as well as the expression of a virulence factor (yrp1) was also determined.

It was demonstrated that PEE has multiple antibacterial mechanisms against Y. ruckeri involving cell wall damage, membrane lysis, and a decrease in gene expression.

The obtained results indicated that the mode of propolis action against Y. ruckeri is both structural and functional, while others showed propolis only could inactivate bacteria in a structural way.