Intercellular Signalling in Vibrio harveyi

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The long term goal of this research is to explore the molecular mechanisms that bacteria use for inter-cellular communication. This project focuses on a study of quorum sensing in the model bioluminescent marine bacterium Vibrio harveyi. It has been demonstrated that V. harveyi has two quorum sensing circuits (Signaling System 1 and Signaling System 2) that converge to regulate light production (Lux). Each system is made up of a two-component sensor-auto-inducer pair: LuxN/AI-1 for System 1 and LuxPQ/AI-2 for System 2. Both sensors transduce information to a shared phosphorelay protein, LuxU, which in turn conveys the signal to the response regulator protein LuxO. Phospho-LuxO is indirectly responsible for repression of luciferase production at low cell density, because it activates the expression of a negative regulator of Lux. A transcriptional activator protein, LuxR, is also required for expression of the luciferase structural operon (luxCDABEGH). Results suggest that V. harveyi uses Signaling System 1 and AI-1 for intra-species communication and Signaling System 2 and AI-2 for inter-species communication. Many bacteria including a number of clinically important pathogens produce AI-2. The goal of this project is to identify and characterize components of the V. harveyi multi-channel quorum sensing signalling pathway, to determine the functions and interactions of the different signalling proteins, and to determine the mechanism of signal integration by the two systems. The analysis of this regulatory network will lead to a molecular understanding of how bacteria integrate, process and transduce sensory information to control gene expression in response to inter-cellular communication. Analysis of this circuit should be valuable for understanding how bacteria perceive and react to their environment, how they communicate with one another and with other species of bacteria, and how they architect elaborate community structures. Since the regulatory process is complex and involves intra-cellular, inter-cellular, intra-species and inter-species signal transmission, interesting new mechanisms could be revealed.