Green fluorescent protein in the design of a living biosensing system for L-arabinose

Analysis of monosaccharides is typically performed using analytical systems that involve a separation step followed by a detection step. The separation step is usually necessary because of the high degree of structural similarity between different monosaccharides. A novel sensing system for monosaccharides is described here in which living bacteria were designed to detect a model monosaccharide, L-arabinose, without the need for a separation step. In such sensing systems, analytes are detected by employing the selective recognition properties found in certain bacterial proteins. These systems are designed so that a reporter protein is expressed by the bacteria in response to the analyte. The concentration of the analyte can be related to the signal generated by the reporter protein. In the sensing system described here, the green fluorescent protein (GFP) was used as the reporter protein. L-Arabinose concentrations can be determined by monitoring the fluorescence emitted by the bacteria at 509 nm after excitation of GFP at 395 nm. The system can detect L-arabinose at concentrations as low as 5 x 10(-7) M and is selective over D-arabinose, the stereoisomer of the analyte, as well as over a variety of pentose and hexose sugars.