Inhibition of quorum sensing-related biofilm of Pseudomonas fluorescens KM121 by Thymus vulgare essential oil and its major bioactive compounds

• Thyme essential oil revealed anti-quorum sensing and anti-biofilm effects.
• Thyme essential oil, carvacrol, and thymol affected bacteria AHLs production.
• The examined agents suppressed flagella gene transcription and the biofilm formation.

The purpose of these investigations was to evaluate the anti-quorum sensing and anti-biofilm potential of Thymus vulgare essential oil (EO) and its respective components. The behavior of the agents tested was validated via examination of their influence on the production of quorum sensing autoinductors (AHLs), motility, flagella (flgA) gene expression, and biofilm formation capacity by model Pseudomonas fluorescens KM121 strain. In this work, Thymus vulgare EO, carvacrol, and thymol at concentrations below the sub-MICs caused significant limitations (i.e., 90%, 80% and 78%, respectively) in the AHLs production in a 72-h-old P. fluorescens KM121 culture. All of the tested agents, which were appreciably effective against P. fluorescens KM121 AHLs production, significantly suppressed bacterial motility and reduced the mRNA level of flagella gene (−0.672, −0.776, and −0.576 for thyme EO, carvacrol and thymol, respectively). Changes in the expression of the AHL-related flgA gene significantly inhibited the biofilm formation on stainless-steel (type 316L) surfaces and only single bacterial cells were presented on the surfaces. The results of the present study propose Thymus vulgare EO as a candidate biocide against food-spoilage P. fluorescens biofilms.