Detection of the antibacterial effect of essential oils on outer membrane proteins of Pseudomonas aeruginosa by lab-on-a-chip and MALDI-TOF/MS

In bacteria, structural changes of outer membrane protein (OMP) composition may have an effect on the adhesive ability and pathogenic properties of the organisms. Pseudomonas aeruginosa can develop an intrinsic resistance to a wide range of biocides, which is associated with the nature of its outer membrane. The aim of our study was to examine how the essential oils of cinnamon bark and clove modify the OMP composition of the human pathogen P. aeruginosa strains and to identify the structure of proteins that are considerably changed after incubation with essential oils. Chemical composition of the oils was analysed by using gas chromatography and gas chromatography-mass spectrometry. Eugenol (83.7%) was the main component of the clove oil, while trans-cinnamic aldehyde (73.2%) was the main constituent in cinnamon bark oil. Values for the minimum inhibitory concentration (MIC) of the oils were determined by a modified tube dilution method. The oils were administered to the culture at concentrations of 0.5xMIC and 2xMIC and incubated for 60 min. After OMP preparation, the structure of proteins was analysed by MALDI-TOF/MS. Cinnamon and clove oil could influence the OMP composition of Pseudomonas strains. Proteins with molecular weights of 42.7 kDa and 79.4 kDa disappeared after treatment with cinnamon and clove oil, respectively. Quantitative changes in the protein profile may contribute to the explanation of the antibacterial effect of cinnamon bark and clove essential oils on pathogenic Pseudomonas strains. Copyright (c) 2013 John Wiley & Sons, Ltd.