Genetic Regulation of Bioluminescence in Marine Bacteria

点击翻译按钮获取中文摘要

9419862 Silverman The objective of this investigation is to understand the genetic control mechanisms which regulate expression of luminescence in the bacterium Vibrio harveyi. Expression of genes for luminescence (lux) in marine bacteria is controlled by cell density and a variety of environmental cues. Density-dependent regulation is a primary facet of lux regulation and is mediated by extracellular signal substances called autoinducers. Two autoinducer signaling pathways converge to control luminescence in V. harveyi. One pathway, signaling system 1, consists of functions for production of autoinducer 1 (AI-1 Signal) and for response to the cognate autoinducer (AI-1 Sensor). The luxL and luxM genes are required for AI-1 production, and luxN encodes the AI-1 Sensor. A second pathway, signaling system 2, consists of functions for production of autoinducer 2 (AI-2 Signal) and for response to this signal (AI-2 Sensor). The luxP and luxQ genes encode AI-2 Sensor proteins. Both signaling pathways intersect at a control function encoded by the luxO gene. The LuxO protein integrates the responses of both Sensors 1 and 2 and, with the participation of the luxR gene product, activates transcription of the luxCDABE operon encoding the luminescence enzymes. Lux regulation is apparently complicated, and many functions and interactions remain to be identified. This project includes mutant isolation to guide the cloning, sequencing and characterization of additional regulatory genes, particularly those required for production of autoinducter 2 (AI-2). Transcripts from various lux regulatory genes are being mapped and quantitated to analyze hierarchical and feedback relationships in the regulatory circuitry. Mutants defective both in sensor 1 and 3 function will be stimulated with a variety of environmental signals to detect cross-communication with other sensory systems. Site-directed mutagenesis will be used to obtain locked or aberrant Lux signaling proteins which will then be used to exam ine interactions of regulatory components and the biochemistry of signal transduction. %%% Analyzing the lux system should be valuable for understanding how bacteria perceive and react to their environment. The regulatory process is complex and involves both intercellular and intracellular signal transmission so interesting new mechanisms could be revealed. However, complexity should not be a barrier because the sensory input (chemical signals) and the output (light emission) can be conveniently controlled and measured, and the genetic methodology is well-developed. ***