1 A novel quorum-sensing system regulating the multicellular behaviour in Serratia marcescens Su-Chen Deng 1‡ , Yu-Tze Horng 1‡ , Mavis Daykin 3 , Po-Chi Soo 1 , Kwen-Tay Luh 2 , Shen-Wu Ho 1,2 , Hsin-Chih Lai 1,2, * ,Simon Swift 3,4,† and Paul Williams 3,4,5 1 School and Graduate Institute of Medical Technology, College of Medicine, National Taiwan University, Taipei, Taiwan, R.O.C. 2 Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan, R.O.C. 3 School of Pharmaceutical Sciences, University Park, University of Nottingham, Nottingham, NG7 2RD, United Kingdom. 4 Institute of Infections and Immunity, and 5 School of Clinical Laboratory Sciences, Queen’s Medical Centre, University of Nottingham, Nottingham, NG7 2UH, United Kingdom. † Present address. Division of Molecular Medicine, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. ‡ Both authors contribute equally to this paper. * For correspondence. Dr. Hsin-Chih Lai, Graduate Institute of Medical Technology, College of Medicine, National Taiwan University, No.1. Chan-Der Street, Taipei 100, Taiwan (R.O.C.). Tel. +886 2 2397 0800 (ext 6931) Fax +886 2 2371 1574 Email: hclai@ha.mc.ntu.edu.tw Running title: Quorum sensing in Serratia marcescens.