Linalool as a Potential Agent for Inhibiting Escherichia coli Biofilm Formation and Exopolysaccharide Production

Abstract Linalool—a compound commonly found in various plant essential oils—exhibits multiple biological activities, encompassing anti-bacterial, inflammatory, analgesic, and antioxidant properties. However, the linalool implications on Escherichia coli (E. coli) biofilm (BF) remain underexplored. We proposed to ascertain the linalool implications on the development of E. coli BF and its extracellular polysaccharides, as well as to assess the implications of linalool on E. coli in both suspension and BF states. We discovered that the minimum biofilm inhibitory concentrations (MBICs) of linalool versus E. coli were twice as high as the lowest inhibitory concentrations. Linalool had a deadly impact on clinical E. coli strains obtained from cows with clinical endometritis, regardless of whether they were in a planktonic or BF condition. Linalool suppressed the BF development in a way that was dependent on the dosage, with an MBIC of 4 µL/mL. This was verified by the use of the crystal violet test and scanning electron microscopy. Moreover, the CCK-8 assay and confocal laser scanning microscopy (CLSM) manifested significant hindrances in live bacteria within the BF. The concentration of extracellular polymeric compounds in the E. coli BF was also mitigated. Furthermore, CLSM and RT-qPCR analysis confirmed that linalool (2 µL/mL) significantly suppressed exopolysaccharide (EPS) and the pgaABCD gene expression, regulating an essential exopolysaccharide expression in BF formation. These findings revealed that linalool effectively suppressed viable bacteria, EPS production, and E. coli BF formation, presenting a new method for preventing BF-related infections.