Effect of Essential Oils on Cell Viability, Membrane Integrity and Membrane Fluidity of Listeria innocua and Escherichia coli
Résumé
Listeria innocua LRGIA 01 and Escherichia coli CECT 471 cells were exposed to five essential oils (EOs) at different concentrations to determine their minimal inhibitory concentrations and minimal bactericidal concentrations. Since bacterial membranes are considered as a target of antimicrobial EOs, the membrane fluidity and integrity of bacteria were monitored respectively after 280 minutes or 24 hours exposure to Laurus nobilis or Satureja calamintha EOs. Measuring fluorescence anisotropy of two probes revealed that these two EOs rigidified the surface of membrane but increased the fluidity of its core. Application of the Live/Dead® BacLightTM kit after 24 hours contact with EOs at their MIC at the bacterial optimal temperature allowed observing that they damaged the membranes of bacteria and the persistence of Viable But Non Culturable (VBNC) bacteria. These observations should both be taken into account when considering addition of EOs to control the growth of certain important food-borne pathogenic bacteria.