"luxab" bioreporters contain only the "luxa" and "luxb" genes, which together are responsible for generating the light signal. however, to fully complete the light-emitting reaction, a substrate must be supplied to the cell. typically, this occurs through the addition of the chemical decanal at some point during the bioassay procedure. numerous "luxab" bioreporters have been constructed within bacterial, yeast, insect, nematode, plant, and mammalian cell systems.