A LuxP-based fluorescent sensor for bacterial autoinducer II.

Autoinducer 2 (AI-2), which enables different bacterial species to engage in interspecies communication, has been difficult to detect quantitatively. Currently, the most commonly used method for AI-2 detection employs an engineered Vibrio harveyi reporter strain, which produces bioluminescence in response to AI-2. However, the bioassay is not quantitative and is sensitive to assay conditions. In this work, we have developed two protein sensors for AI-2 by modifying AI-2 receptor proteins LuxP and LsrB with environmentally sensitive fluorescent dyes. The protein sensors bind specifically to AI-2 and produce dose-dependent changes in their fluorescence yield. The new assay method has been applied to monitor the enzymatic synthesis of AI-2 in real time and determine the extracellular and intracellular AI-2 concentrations in several bacterial culture fluids.