Vibrio vulnificus
A Microbial Biorealm page on the genus Vibrio vulnificus
Classification
Higher order taxa
Bacteria; Proteobacteria; Gammaproteobacteria; Vibrionales; Vibrionaceae; Vibrio
Species
Vibrio vulnificus
Description and significance
V. vulnificus, a gram negative, rod shaped, halophile, is a virulent bacterium associated with about 95 percent of all seafood related deaths. It is a human pathogen known to cause gastroenteritis, wound infections and primary septicemia. This organism can typically be found in estuarine and coastal waters, thriving especially in bivalve mollusks including oysters and clams, additionally, causing health risks to those who ingest raw or undercooked seafood.
V. vulnificus has three biotypes, with biotype one, identified as a new species in 1976, caused the greatest public health concern, with its involvement with human disease. Furthermore, biotype two is associated with infected eels, and biotype three is associated with wound infections of humans.
Genome structure
The genomes of two strains of V. vulnificus, YJ016 and CMCP6, have been fully sequenced, each with two, circular chromosomes.
Chromosome I of strain YJ016 has a length of 3,354,505 nucleotides, while chromosome II contains 1,857,073 nucleotides, with a size of 5,260,086 base pairs.
Chromosome I of strain CMCP6 has 3,281,945 nucleotides in length, while chromosome II has 1,844,853 nucleotides, with a size of 5,126,798 base pairs.
It is believed that Vibrios have two chromosomes as an evolutionary advantage. The larger chromosome plays a role in growth, while the smaller one is involved in adaptation and environmental change. Phenotypic variation is also present within V. vulnificus. It is observed that no two strains are genetically identical.
Cell structure and metabolism
V. vulnificus is a gram negative bacterium. It contains pili for motility, adherence to epithelial cells and is involved in biofilm formation. Some strains contain capsules which determine virulence and are also associated with biofilm formation. In addition, iron is an important factor for growth and siderophores are produced to deliver the iron to the bacteria.
This organism is also known to be “lactose-positive” with its fermentation of lactose, salicin and cellobiose. But since phenotypic variation is observed, about 15% of strains were found to be lactose negative and another 15% were found to be sucrose positive.
In addition, this bacterium is an also known halophile, and usually grows in areas with a minimum of 5% salinity.
Endotoxin, found on lipopolysaccharides, is the major cause for this organism’s virulence and is the leading factor which causes shock or death in an infected individual.
Ecology
V. vulnificus has a generalized stress response. Depending on its environment, changes induce production of heat shock proteins in response to different temperatures, changes in osmolarity, the presence of pollutants, or its interactions with other organisms. With the production of these proteins, the bacteria may adapt comfortably in its environment.
Typically, more of this organism can be found in waters during the summer months, with its optimal temperature being between 20 to 30 degrees Celsius. Furthermore, V. vulnificus, a halophile, can naturally be found in waters with 5% salinity.
Other marine sources for this bacterium, other than water and shell fish, also include plankton, other types of fish and isolated sediment.
Pathology
This bacterium may infect an individual if ingested or can enter the body through an open wound. From there, it invades the GI tract or blood and can lead to septicemia, depending if the person is healthy or has a vulnerable immune system. Symptoms of invasion include blister-like lesions on the skin. Other symptoms also include fever, nausea or gastroenteritis.
V. vulnificus has a significant number of potential determinants of virulence. Some determinants include the presence of a capsule to avoid host phagocytosis, or Type IV pili used to attach to host cells, or for iron transfer or biofilm formation. Another major determinant for virulence is the presence of lipopolysaccharides, an endotoxin, which are responsible for septicemia, shock and even death.
On the contrary, biotype two is associated exclusively with eels, causing eel vibriosis or death, regardless of the presence of a capsule on the bacterium. This type differs from biotype one in other ways including the production of exoproteins and the O-antigenic side chain on the lipopolysaccharide molecule.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
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References
"Vibrio". National Microbial Pathogen Data Resource Center.
Todar, Kenneth. "Vibrio vulnificus". Todar's Online Textbook of Bacteriology. 2005.
[ Thompson, F., Austin, B., and Swings, J. (Eds.). (2006). The Biology of vibrios. (pp. 349-354, 359-361). Washington, D.C.: ASM Press.]
Edited by Kristine Yambao, student of Rachel Larsen and Kit Pogliano