Then the microbial levels can be determined. Even with this extra step, the test is much swifter than conventional microbial testing, which takes 24 to 48 hours. Because ATP bioluminescence can indicate the presence of food residues, it is also particularly useful for rapidly determining if the food preparation and processing environment is clean. Another bioluminescence test method involves the use of genetic engineering, the transfer of genes from one organism into another. In bacterial bioluminescence, scientists take the gene sequence responsible for creating the light-emitting enzyme luciferase out of a particular type of bacterium.
Viruses can be very useful for identifying specific bacteria.
In this case, the virus is used as a vector, or carrier, of the enzyme. The enzyme doesn't create light when it is in the virus. But when the virus infects its host, for example the salmonella, the spliced enzyme genes cause the salmonella bacteria to glow. Devices such as these which combine a rapid detection system with a microprocessor to provide the results of a specific biological reaction are called biosensors. Using the luminometer, a reading of bacteria levels can be obtained in a few seconds.