Can your spit glow? Let’s hope not – because if it did, you’d have eaten fish contaminated by photobacteria!
Photobacteria are comma-shaped bacteria that have the property bioluminescence. This means that they give off light, usuafishlly a blue or green. There are about 15 species of bacteria that fall into this group. Photobacteria generally live in the ocean, where they survive off of sodium. Remember that salt, or sodium chloride, is made of the elements sodium and chlorine, so the salt water of the ocean is a good place to find sodium. These organisms appear to be clear under normal circumstances.
Photobacteria sometimes are found alone, and other times are found in large colonies. Their most distinctive quality, that of bioluminescence, is triggered by autoinducers. Autoinducers are molecules that signal the production of certain chemicals (in this case chemicals that lead to the release of light) in bacteria. In photobacteria, autoinducers are related to the density of the bacteria. In other words, the more bacteria present, the more of an impact the autoinducers will have. For this reason, it is only when they are in large colonies to the bacteria give off light.
Photobacteria can have relationships with fish that can be positive, neutral, or negative for the fish. Some photobacteria help fish by providing them light organs. Other times, the bacteria are found on the intestines of fish, really not affecting things one way or the other. Some photobacteria are pathogens, which means they can cause disease in fish. Yellowfin tuna, striped bass, and white carp are especially at risk for the diseases caused by photobacteria. So, although humans are not directly at risk from these diseases, they can indirectly be affected when the fish many people rely on for food become sick. Additionally, dying fish can lead to the loss of a great amount of money when fishermen are no longer able to catch as many fish as they were previously. A great deal of research has been done trying to find ways to control photobacteria populations.