Abstract: The inventive technology may include a tripartite fluorescent resonance energy transfer (FRET) based fusion protein complex having a ligand binding domain capable of binding to a target ligand and coupled with a donor-acceptor pair of chromophores moieties. The ligand binding domain may be positioned between the donor and acceptor chromophore moieties and may further bind to another ligand binding domain forming a homodimer complex. Ligand binding may cause dissociation of the homodimer complex leading to enhanced donor fluorescence emission and simultaneous quenching of the acceptor fluorescence emission, yielding significant decreases in the acceptor-to-donor fluorescence emission ratio. The tripartite FRET based fusion protein may be used as a biosensor, preferably for molecules responsible for bacterial quorum sensing.