A-057. Effect of Thymol on Total Proteome of Salmonella enterica serovar Thompson

R. Di Pasqua1, G. Mamone2, P. Ferranti1, M. Lamberti1, D. Ercolini1, G. Mauriello1;
1Univ. degli Studi di Napoli Federico II, Portici, ITALY, 2Istituto di Scienze dell'Alimentazione - Centro Nazionale delle Ricerche, Avellino, ITALY.

Background: Thymol is a natural biocide and component of some essential oils from herbs. Its inhibitory effect on the growth of different microorganisms is well known, while less known is its mechanism of action towards microbial cells. Of course that depends on the target microorganism as well as environmental conditions. The response of bacteria grown in presence of thymol has not been investigated satisfactorily although its known that a modification of membrane fatty acids composition is caused. However, it remains to be assessed whether the modifications in membrane composition really lead to an increased resistance or are just part of a general adaptive response. Methods: A strain of Salmonella enterica serovar Thompson (MCV1), isolated from poultry, has been grown in presence of a sublethal concentration (0.01%) of thymol. After growth the cells have been processed for total proteins extraction and the extracts from treated and untreated cells were subjected to two-dimensional polyacrylamide gel electrophoresis (2D-SDS PAGE), followed by in-gel digestion of spot and subsequent MALDI-TOF analysis. Results: The analysis of gels showed many proteins that were either up- or down-regulated by the presence of thymol, with significant changes in proteins belonging to different functional classes: glucose and fatty acid metabolism, molecular chaperones, protein and aminoacid biosynthesis, transcription regulation, chemotaxis and cell adhesion. The global response regulator protein (arcA), essential for resistance of the cells to reactive nitrogen and oxygen intermediates (ROI and RNI), and the outer membrane protein X (OmpX) have been found up-regulated in treated cells. The concurrent up-regulation of these two proteins is associated with an increase of the resistance at different stress conditions. The regulation of these proteins plays an important role in the acid adaptation and general stress tolerance. Conclusion: It can be concluded that the regulation of the listed classes of proteins concur to the adaptive response activated by the cells to withstand the adverse environmental conditions beyond resulting in promotion of cross-resistance to other environmental stresses.