Harnessing nature’s glow of bioluminescent bacteria

Bioluminescence, the emission of light by living organisms, has always attracted the attention of scientists because of their inherent beauty and ease of detection. Like fireflies, there are different species of glow-in-the-dark bacteria as well. They are widely distributed, inhabiting terrestrial, freshwater and marine ecosystems.A recurring question among researchers in the past has been what the biological significance of bioluminescence is. And how does it happen? The purposes of bioluminescence include attracting prey, mates, driving away predators and even as a mode of communication. It happens via a series of chemical reactions occurring in living cells, as opposed to the absorption of photons as happens in fluorescence.  
While most species of luminescent bacteria live freely, the majority are found in nature, associated in symbiosis with host organisms. One example is the luminescent bacteria found in the esca of the anglerfish, the pouch which hangs from the fish’s head. This light pouch attracts prey. It is a mutualistic relationship where the fish in turn provide the necessary nutrients and a safe habitat for the bioluminescent bacteria living in its esca.  During the American Civil War, there were reports of soldiers who developed glowing wounds. Those who had these glowing wounds were more likely to survive. This was called ‘the angel’s glow’. The wounds had been contaminated with bioluminescent bacteria from the soil and the antibiotics they produced prevented other harmful bacteria from infecting the wounds.  
Each species of luminous bacteria differs in their properties, including the specific growing conditions (nutritional requirements and growth temperature) and the reaction kinetics of the luciferase involved in light generation. All luminous bacteria though are rod-shaped, gram-negative microorganisms, with flagella facilitating motion.  
The catalytic machinery involved in continuous light production in luminous bacteria includes not only bacterial luciferase but also enzymes that supply and regenerate the substrates of bacterial luciferase. Bacterial luciferase is coded by genes found in the Lux operon. The luciferase is coded by genes.  
This naturally-occurring phenomenon of bioluminescent bacteria is made use of in scientific research. Mainly they act as biosensors. The fact that only the living bacterial cells will produce light is the basis of these experiments. They are used in measuring the efficacy of fast-acting biocides. They are also used in antibiotic testing. The ability of these glowing bacteria to act as biosensors is involved in measuring the levels of different toxins in the environment. A fascinating ongoing study tries to determine whether these minute light-emitting bacteria can be utilized in such a way as to minimize the usage of electricity. These bacteria could make glowing trees that could light streets and replace streetlamps. Two independent lines of Nicotianatabacum transplastomic plants, carrying the bacterial lux operon from Photobacterium leiognathi has been generated. What has enabled the expression of this prokaryotic operon in plants is the evolutionary conservation of the prokaryotic gene expression machinery in chloroplasts. Bacterial bioluminescence is indeed an interesting field 
of study!  
P.H.A.P.L. Jayatilake
Microbiology (special) degree
University of Sri Jayawardenepura