Designed by: Wei Chung Kong   Group: iGEM15_Oxford15   (2015-08-28)

pLsr + RBS + sfGFP

This composite part consists of the AI-2 quorum sensor-inducible promoter BBa_K117002, a weak ribosome binding site BBa_B0031, and a GFP coding sequence BBa_I746916.


The Lsr quorum sensing pathway is a non-species specific cell-to-cell communication pathway used by both Gram-positive and Gram-negative bacteria and is found in at least 55 strains of them, most notably strains of E. coli, S. typhimurium, and V. harveyi [1][2]. Production of the chemical messenger AI-2 is mediated by the enzymes Pfs and LuxS, which metabolizes the toxic metabolic product S-adenosylhomocysteine (SAH) in a stepwise manner to form AI-2 [3].

The transporter protein cluster LsrACDB (depicted as the gray channel through which AI-2 passes to enter the host cell) facilitates the uptake of AI-2 [4]. LsrR represses the pLsr promoter, which endogeneously is upstream of the lsrACDBFG and lsrRK operons, but in the context of synthetic biology can be placed upstream of any coding sequence of interest. LsrK phosphorylates and hence activates AI-2, allowing it to bind to LsrR and relieve its repression on pLsr, thus inducing the expression of the gene downstream of pLsr via an indirect mechanism [4].


Quorum sensing coordinates key cooperative behaviours in bacteria, including the formation of biofilms [3]. As we are interested in urinary tract infections involving biofilms, we linked an existing GFP part downstream of this pLsr promoter which is also an existing part in the Registry to test the promoter's function and gather some preliminary data to help us explore the possibility of integrating a quorum sensing element into our antibiofilm/antibacterial secretion design to create a pathogen-responsive autonomous setup.


[1] Surette, M.G., Miller, M.B. & Bassler, B.L., 1999. Quorum sensing in Escherichia coli, Salmonella typhimurium, and Vibrio harveyi: a new family of genes responsible for autoinducer production. Proceedings of the National Academy of Sciences of the United States of America, 96(4), pp.1639–1644.

[2] Bassler, B.L., Greenberg, E.P. & Stevens, A.M., 1997. Cross-species induction of luminescence in the quorum-sensing bacterium Vibrio harveyi. Journal of Bacteriology, 179(12), pp.4043–4045.

[3] Brito, P.H. et al., 2013. Natural genome diversity of AI-2 quorum sensing in Escherichia coli: Conserved signal production but labile signal reception. Genome Biology and Evolution, 5(1), pp.16–30.

[4] Li, J. et al., 2007. Quorum sensing in Escherichia coli is signaled by AI-2/LsrR: Effects on small RNA and biofilm architecture. Journal of Bacteriology, 189(16), pp.6011–6020.