Increased application of ionic liquids (ILs) in various chemical and biochemical processes as well as for pharmaceuticals or antimicrobial agents has prompted researchers to assess their biological functions, especially their toxicity. However, to date the molecular mechanisms underlying tolerance of certain bacterial species to ILs has not been studied in detail. The recently found transposon Tn6188 in Listeria monocytogenes has been shown to mediate tolerance to quaternary ammonium compounds (QACs) such as benzalkonium chloride, which are widely used as disinfectants in food processing plants, via QacH, a small multidrug resistance protein family (SMR) transporter. In this study the possible Tn6188 mediated tolerance of L. monocytogenes to ILs was investigated. It was found that Tn6188 confers tolerance of L. monocytogenes to ILs based on imidazolium and ammonium cations. (C) 2015 Elsevier B.V. All rights reserved.