BIOTECHNOLOGICALLY RELEVANT ENZYMES AND PROTEINS Furanone derivatives as quorum-sensing antagonists of Pseudomonas aeruginosa Cheoljin Kim & Jaeeun Kim & Hyung-Yeon Park & Hee-Jin Park & Joon Hee Lee & Chan Kyung Kim & Jeyong Yoon Received: 21 January 2008 / Revised: 27 March 2008 / Accepted: 27 March 2008 / Published online: 20 June 2008 # Springer-Verlag 2008 Abstract The biofilm formation of Pseudomonas aerugi- nosa, an opportunistic human pathogen, is developed by cell-to-cell signaling, so-called quorum sensing (QS). To control the biofilm formation, we designed and synthesized new QS inhibitors of P. aeruginosa based on the structure of the previously known QS inhibitor, furanone. Newly synthesized compounds were a series of analogs of (5-oxo- 2,5-dihydrofuran-3-yl)methyl alkanoate, and the structures of all six synthesized compounds was confirmed by NMR and GC/MS analyses. These new QS inhibitor candidates could remarkably inhibit both Pseudomonas QS signaling and biofilm formation, which were assayed by using the recombinant reporter system and flow cell confocal microscopy. The degree of QS inhibition by these new inhibitors varied from 20% to 90%. For the profound understanding about inhibition mechanism, we tried to estimate the binding energy between QS receptor, LasR, and our inhibitors from the in silico modeling system. The predicted binding pattern from the modeling system and our experimental data about QS inhibition were in good agreement. From these results, we suggest a new approach to develop the QS inhibitors and biofilm control agents based on structural modeling. Keywords Quorum-sensing inhibitors . Cell-to-cell communication . Furanone derivatives . FlexX docking . Binding energies (docking score) Introduction The quorum-sensing (QS) regulation of bacterial genes is achieved by signals, signal–synthases, and signal–receptor proteins (McDougald et al. 2007). The cell density-depen- dent increase of signal concentration is sensed by receptors and the receptor-related regulators trigger the expression of target genes. Because the expressions of signal synthase genes and receptor-regulator genes are also induced during this process, the QS phenomenon and its signals have been described as “autoinduction” and “autoinducers,” respec- tively (Grabski et al. 2005). The opportunistic pathogen, Pseudomonas aeruginosa, uses QS to develop the patho- genic process where the production of many virulence factors causing diseases is regulated by QS. Notably in the chronic infection such as cystic fibrosis, P. aeruginosa forms biofilm under the control of QS (Singh et al. 2000). Biofilm is a structured community of microbial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface. This is a very protective and persistent mode of life which allows survival in hostile environments. Some biofilms are beneficial, for example aiding water clean-up process, but other biofilms are extremely harmful. About 65% of infective diseases are Appl Microbiol Biotechnol (2008) 80:37–47 DOI 10.1007/s00253-008-1474-6 C. Kim : J. Kim : H.-J. Park : J. Yoon (*) School of Chemical and Biological Engineering, Seoul National University, San 56-1, Sillim-dong, Gwanak-gu, Seoul 151-742, South Korea e-mail: jeyong@snu.ac.kr H.-Y. Park : C. K. Kim Department of Chemistry, College of Natural Science, Inha University, 253, Yonghyun-dong, Nam-gu, Incheon 402-751, South Korea J. H. Lee Department of Pharmacy, College of Pharmacy, Pusan National University, Geum Jeong-gu, Busan 609-735, South Korea