title: Prediction by promoter logic in bacterial quorum sensing.
abstract: Quorum-sensing systems mediate chemical communication between bacterial cells, coordinating cell-density-dependent processes like biofilm formation and virulence-factor expression. In the proteobacterial LuxI/LuxR quorum sensing paradigm, a signaling molecule generated by an enzyme (LuxI) diffuses between cells and allosterically stimulates a transcriptional regulator (LuxR) to activate its cognate promoter (pR). By expressing either LuxI or LuxR in positive feedback from pR, these versatile systems can generate smooth (monostable) or abrupt (bistable) density-dependent responses to suit the ecological context. Here we combine theory and experiment to demonstrate that the promoter logic of pR - its measured activity as a function of LuxI and LuxR levels - contains all the biochemical information required to quantitatively predict the responses of such feedback loops. The interplay of promoter logic with feedback topology underlies the versatility of the LuxI/LuxR paradigm: LuxR and LuxI positive-feedback systems show dramatically different responses, while a dual positive/negative-feedback system displays synchronized oscillations. These results highlight the dual utility of promoter logic: to probe microscopic parameters and predict macroscopic phenotype.
authors.affiliation: National Centre for Biological Sciences, Tata Institute of Fundamental Research, UAS/GKVK Campus, Bangalore, India.
authors.forename: Navneet
authors.initials: N
authors.lastname: Rai
authors.forename: Rajat
authors.initials: R
authors.lastname: Anand
authors.forename: Krishna
authors.initials: K
authors.lastname: Ramkumar
authors.forename: Varun
authors.initials: V
authors.lastname: Sreenivasan
authors.forename: Sugat
authors.initials: S
authors.lastname: Dabholkar
authors.forename: K V
authors.initials: KV
authors.lastname: Venkatesh
authors.forename: Mukund
authors.initials: M
authors.lastname: Thattai
mesh_terms: D048908:Aliivibrio fischeri / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology; D025461:Feedback, Physiological; D015964:Gene Expression Regulation, Bacterial; D008957:Models, Genetic; D015233:Models, Statistical; D011401:Promoter Regions, Genetic; D053038:Quorum Sensing / Q000235:genetics*; D015398:Signal Transduction