text: The uses of bioluminescence and its biological and ecological significance for animals, including host organisms for bacteria symbiosis, have been widely studied. The biological role and evolutionary history for specifically bioluminescent bacteria still remains quite mysterious and unclear. However, there are continually new studies being done to determine the impacts that bacterial bioluminescence can have on our constantly changing environment and society. Aside from the many scientific and medical uses, scientists have also recently begun to come together with artists and designers to explore new ways of incorporating bioluminescent bacteria, as well as bioluminescent plants, into urban light sources to reduce the need for electricity. They have also begun to use bioluminescent bacteria as a form of art and urban design for the wonder and enjoyment of human society.
  One explanation for the role of bacterial bioluminescence is from the biochemical aspect. Several studies have shown the biochemical roles of the luminescence pathway. It can function as an alternate pathway for electron flow under low oxygen concentration, which can be advantageous when no fermentable substrate is available. In this process, light emission is a side product of the metabolism.
  Evidence also suggests that bacterial luciferase contributes to the resistance of oxidative stress. In laboratory culture, luxA and luxB mutants of Vibrio harveyi, which lacked luciferase activity, showed impairment of growth under high oxidative stress compared to wild type. The luxD mutants, which had an unaffected luciferase but were unable to produce luminescence, showed little or no difference. This suggests that luciferase mediates the detoxification of reactive oxygen.
  Bacterial bioluminescence has also been proposed to be a source of internal light in photoreactivation, a DNA repair process carried out by photolyase. Experiments have shown that non-luminescent V. harveyi mutants are more sensitive to UV irradiation, suggesting the existence of a bioluminescent-mediated DNA repair system.
  Another hypothesis, called the "bait hypothesis", is that bacterial bioluminescence attracts predators who will assist in their dispersal. They are either directly ingested by fish or indirectly ingested by zooplankton that will eventually be consumed by higher trophic levels. Ultimately, this may allow passage into the fish gut, a nutrient-rich environment where the bacteria can divide, be excreted, and continue their cycle. Experiments using luminescent Photobacterium leiognathi and non-luminescent mutants have shown that luminescence attracts zooplankton and fish, thus supporting this hypothesis.