From Communication to Collapse: Targeting Bacterial Biofilms with Essential Oils

Bacterial biofilms represent an evolutionary adaptation that enables a shift from a free-living to a cooperative, community-based lifestyle. Within these structures, heterogeneous microbial populations are packaged in a self-produced matrix of extracellular polymeric substances (EPSs), which significantly enhances their resilience, virulence, and persistence across clinical, environmental, and food-related environments. The transition to this hierarchical lifestyle is derived from a multifactorial process centred on Quorum sensing (QS), wherein the exchange of small signalling molecules promotes intercellular communication, and the synchronised expression of genes involved in pathogenicity and antimicrobial resistance. The tolerance exhibited by biofilm-associated cells to environmental stresses and antimicrobials is a non-heritable trait, largely attributed to the protective properties of the EPS matrix, which can inactivate or limit the diffusion of antimicrobial agents. As biofilms continue to pose a global threat, there is a growing demand for innovative and sustainable control strategies. Essential oils (EOs) have gained attention as promising natural antimicrobials due to their multicomponent nature, broad-spectrum activities, and counteraction of bacterial resistance. This review explores the anti-biofilm activity of EOs, with a particular focus on their molecular mechanisms of action against key foodborne pathogens, including Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enterica, and Staphylococcus aureus, by targeting genes involved in QS regulation, motility, adhesion, and virulence.