Bacteria are proving to be much more useful than might have been thought a couple hundred years ago. Photobacterium phosphoreum has proved to be one of these useful bacteria. The genus Photobacterium is made of gram-negative cells, which are small, plump, and rod shaped. The cells have one to three unsheathed flagella that provide the power for movement (Balows 3001). The cells’ optimal growth temperature is 18-25 ?C (Simonton). P. phosphoreum has been found in both seawater and freshwater. However, it seems to prefer the seawater environment (Budsberg). P. phosphoreum is one of many bioluminescent microbes that are now known. The fact that these microbes are able to produce their own light is amazing, but the microbial role of some of these microbes is even more astonishing.
The general method of producing the light is fairly common among many of the bioluminescent microbes. The process of light production begins with the reduction of luciferin by the oxidation of NADH2 to NAD. The reduced luciferin then forms a complex with the enzyme luciferase. Oxygen reacts with this complex to yield water, oxidized luciferin (oxyluciferin), and an excited state of luciferase. As the excited luciferase decays back down to its base energy level, it gives off energy in the form of light in the process, and thereby fulfills the bioluminescence process (Madden). Note that because oxygen plays a crucial role in this process, it is required in order for the bioluminescent process to occur (Eddleman).
One of the more natural roles that P. phosphoreum plays, is its interaction with marine life. P. phosphoreum will sometimes act as a parasite and live within or on a marine animal. Other bioluminescent microbes also do this (Eddleman). The microbes provide a source of light to the animals in this situation in return for a safe environment and nutrients. The luminescence can be used by the animals to both attract prey and escape from predators (“Bacteria”; Bluth). Another use or role of P. phosphoreum is its ability to signal the relative toxicity of substances. The light producing process described above is connected to the cellular metabolism. Therefore if a toxin changes or harms a part of the metabolism process, the strength of luminescence will also change (decrease if harm is done). By measuring the luminescence strength, it is possible to get an estimate of the relative toxicity of a substance compared to a known sample. One marketed bioassay that uses this method is Microtox?. Microtox? only takes five to thirty minutes to complete, and therefore represents a very convenient and quick preliminary test for toxicity (“Microtox”).
Bioluminescent microbes such as P. phosphoreum are very promising for the future. In addition to continuing the traditional parasite-host interaction with marine animals, these microbes seem to be perfect for field applications, in which quick toxicity determinations need to be carried out before further action can take place. P. phosphoreum could even end up being the major component of the first widely marketed biological flashlight. Who knows what the future will bring.
References:
“Bacteria.” Harbor Branch Oceanographic Institution. 21 Feb. 2005.
<http://www.biolum.org/>.Balows, Albert et al., Ed. The Prokaryotes. NewYork: Springer-Verlag, 1992. Vol. 3, p. 3001.
Bluth, Brian, Sarah Frew, and Brian McNally. “Cell-Cell Communication and the lux operon in Vibrio fischeri: Introduction to Bioluminescence.” 21 Feb. 2005.
<http://www.bio.cmu.edu/courses/03441/TermPapers/97TermPapers/lux/default.html>.Budsberg, K.J., C.F. Wimpee, and J.F. Braddock. “Isolation and Identification of Photobacterium phosphoreum from an Unexpected Niche: Migrating Salmon.” Applied and Environmental Microbiology. 6 Aug. 2003. 20 Feb. 2005. <http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=262280>.
Eddleman, Harold. “Isolation of Pure Cultures of Bacteria: Vibrio phosphoreum from Squid or Ocean Fish.” 9 Sep. 1999. 20 Feb 2005. <http://www.disknet.com/indiana_biolab/b203.htm>.
Madden, Dean, Britt-Marie Lidesten. “Bacterial Illumination: Culturing luminous bacteria.” Bioscience Explained. Vol. 1; No. 1: 2001. 21 Feb. 2005.
<www.bioscience-explained.org>.“Microtox Bioassay Testing System.” 20 Feb. 2005. <http://www.alaska.net/~aknafws/text/micro.html>.
Simonton, Rebecca. “Photobacterium-An Overview.” 21 Feb. 2005. <http://soils1.cses.vt.edu/ch/biol_4684/Microbes/inbrief.html>.
*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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