Vibrio harveyi
Charles Bowe

Vibrio harveyi is a gram negative bacterium that is found in marine habitats. It is a gamma proteobacteria, of the Vibrionaceae family. It is a rod shaped facultative anaerobe, does not produce spores, and has a group of flagella on one end which are covered in a sheath. Normal dimensions are around .5 microns by 2 microns. It can be found free living or living symbiotically with things such as shrimp and octopuses. It is bioluminescent.

Although found living symbiotically with many organisms, it is known to cause Luminous vibriosis, a disease that causes death in invertebrates. This has become a big problem with the amount of commercially farmed marine invertebrates there are, often ruining a farmers yield.

One thing that this bacterium is used for is for its bioluminescent genes. Like many other bioluminescent bacteria its genome has been mapped, and so we know what genes cause it to be bioluminescent and how the proteins work. Basically it works via an enzyme called luciferase, which causes the oxidation of a pigment called luciferin, which gives off a blueish light. Scientist can use these genes to couple the bioluminescent response to other genes, using them as a way to do things like detecting transcriptional activity and even measuring cell viability by checking ATP levels. But why bioluminesce? It is possible that is has to do with DNA repair. By bioluminescing the bacteria could activate its own photolyases, which repair pyrimidine dimmers caused by UV damage and require light to be activated.

Another thing Vibrio harveyi is often used for is research into something called quorum sensing. Quorum sensing is basically mass communication done by decentralized groups. Meaning is a way for all the Vibrio harveyi around each other to communicate. In Vibrio harveyi’s case it is used to, among other things, trigger bioluminescence. It does this by sending out a chemical signal that eventually causes the transcription of the bioluminescent genes. This bacterias genes for quorum sensing were one of the first mapped and thus is one of the most often studied species in this area.

One interesting phenomenon that is associated with Vibrio harveyi is the Milky Seas Effect. This is a result of their bioluminesences and quorom sensing. Apparently on occasion massive groups of these bacteria can be seen giving off light at night in the sea, causing very large areas of the sea to glow, up to 6000 square miles! This is so big that it can be seen from space.



*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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