Vibrio fischeri: Difference between revisions

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Infections associated with noncholera Vibrio species are gastroenteritis, wound infection and septicemia.  ''V vulnificus'' is responsible for causing septicemia.  Several mechanisms contribute to the virulence of ''Vibrio vulnificus''. For instance, iron is an important growth factor. However, because free iron is absent in humans, ''Vibrio vulnificus'' produces siderophores that acquire iron from transferrin or lactoferrin and deliver it to the bacteria. The inability to produce siderophores leads to the reduction of virulence. Among all foodborne diseases, ''Vibrio vulnificus'' infection is linked with the highest case fatality rate.
Infections associated with noncholera Vibrio species are gastroenteritis, wound infection and septicemia.  ''V vulnificus'' is responsible for causing septicemia.  Several mechanisms contribute to the virulence of ''Vibrio vulnificus''. For instance, iron is an important growth factor. However, because free iron is absent in humans, ''Vibrio vulnificus'' produces siderophores that acquire iron from transferrin or lactoferrin and deliver it to the bacteria. The inability to produce siderophores leads to the reduction of virulence. Among all foodborne diseases, ''Vibrio vulnificus'' infection is linked with the highest case fatality rate.
Patient symptoms associated with gastroenteritis include diarrhea, abdominal cramps, nausea, vomiting, headaches, bloody stools, etc.  Symptoms associated with noncholera wound infection include swelling, pain, erythema, bullae, and necrosis.  And symptoms associated with septicemia include fever, hypothermia, hypotension, acute respiratory distress syndrome, and multiple organ dysfunction.


==Application to Biotechnology==
==Application to Biotechnology==

Revision as of 18:13, 28 April 2007

A Microbial Biorealm page on the genus Vibrio fischeri

Classification

Higher order taxa

Bacteria; Proteobacteria; Gammaproteobacteria; Vibrionales; Vibrionaceae; Vibrio; Vibrio fischeri

Species

Vibrio fischeri

Description and significance

The family Vibrionaceae are natural inhabitants of seawater but can be found in fresh water. Vibrio fischeri, a species of bioluminescent bacterium, is frequently found in symbiotic relationships with marine animals like the bobtail squid. Their bioluminescence stems from their expression of a series of proteins contained in the lux operon.

Genome structure

The genome of Vibrio fischeri strain ES114 consists of 4,284,050 bp. Approximately 61.6% of the genome is AT rich and its coding density is 86.2% (1129 bp/gene). It contains two chromosomes both of which are circular. Chromosome 1 is 2,906,179 bp and chromosome 2 is 1,332,022 bp. This strain of bacteria is characterized by a 45.8 kbp plasmid (cir) called pES100. The pES100 plasmid encodes a putative type IV secretion system. The carriage of a plasmid that is similar to the pES100 plasmid is common among symbiotic strains of Vibrio fischeri, but is not required for host association.

Cell structure and metabolism

Vibrio fischeri is a gram negative bacteria composed of a cell wall that consists of an outer membrane containing lipopolysaccharides, a periplasmic space with a peptidoglycan layer, and an inner, cytoplasmic membrane.

One of its most distinguishing characteristics, bioluminescence, is controlled by a small set of genes known as the lux operon.

Luminescence is a chemical reaction in which the enzyme, luciferase, oxidizes organic compounds, such as long chain aldehyde and reduced flavin mononucleotide, so as to release energy in the form of blue-green light at 490nm. The reaction that occurs in Vibrio fischeri is as follows: FMNH2 + RCHO + O2 --> FMN + RCOOH + H2O + hv(490nm)

The lux operon is a 9 kb fragment that consists of genes that code for the subunits of luciferase (luxAB) and for enzymes (luxCDE) that convert compounds to oxidizable substrates. This 9 kb fragment includes all that is necessary to carry out the functions of luminescence in other organisms such as E. Coli. It has been found that expression of luminescence is dependent on cell density and thus light is not seen unless the bacteria are in high concentration, like in light emitting organs of fish and squid. This phenomenon is known as quorum sensing.

The rationale behind quorum sensing has to do with the proteins encoded on the lux operon. The lux operon is actually set up like two differently transcribed operons. As mentioned before, luxA and luxB code for the subunits of the enzyme luciferase. LuxCDE codes for enzymes that convert fatty acids into aldehydes which are needed for the reaction to proceed. These genes, in addition to luxI and luxG, make up one operon. LuxI is at the head of this first operon and is responsible for the production of the auto inducer protein. This is the molecule that is involved in sensing the concentration of bacterium in a space. This protein can easily diffuse out of the cell, and if Vibrio fischeri were found floating freely in the ocean, as is sometimes seen, this auto inducer would diffuse out of the cell and float away. However, when in a restricted space, it is forced to react with the protein produced from the second operon, the regulator, luxR. This results in increasing the affinity of RNA polymerase to the promoter region of the first operon and eventually producing luminescence.

Ecology

Luminescent bacteria are found in free-living, symbiotic, saprophytic or parasitic relationships. The symbiotic relationship between the squid and Vibrio fischeri provides an example of specific cooperativity during the development and growth of both organisms. For instance, once the squid becomes infected with Vibrio fischeri, maturation of the light organs begin. Vibrio fischeri are helpful to the squid, a nocturnal forager, by erasing the shadow that would normally be seen as the moon's rays strike the squid, protecting the squid from its predators. The squid, in turn, provide the bacteria with shelter and a stable source of nutrients.

Pathology

Among the Vibrio species that are capable of causing human disease, there are two main groups: Vibrio cholerae infection and noncholera Vibrio infections. Vibrio infections are often characterized as a foodborne disease as a result of consumption of contaminated seafood, exposure of wounds to contaminated seawater, or injury caused by shark and alligator bites.

Infections associated with noncholera Vibrio species are gastroenteritis, wound infection and septicemia. V vulnificus is responsible for causing septicemia. Several mechanisms contribute to the virulence of Vibrio vulnificus. For instance, iron is an important growth factor. However, because free iron is absent in humans, Vibrio vulnificus produces siderophores that acquire iron from transferrin or lactoferrin and deliver it to the bacteria. The inability to produce siderophores leads to the reduction of virulence. Among all foodborne diseases, Vibrio vulnificus infection is linked with the highest case fatality rate.

Patient symptoms associated with gastroenteritis include diarrhea, abdominal cramps, nausea, vomiting, headaches, bloody stools, etc. Symptoms associated with noncholera wound infection include swelling, pain, erythema, bullae, and necrosis. And symptoms associated with septicemia include fever, hypothermia, hypotension, acute respiratory distress syndrome, and multiple organ dysfunction.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

References

Hallin PF, Ussery DW (2004). "CBS Genome Atlas Database: A dynamic storage for bioinformatic results and sequence data." Bioinformatics. 2004 Dec 12;20(18):3682-6. Epub 2004 Jul 15.

Ruby, E.G., Urbanowski, M., Campbell, J., Dunn, A., Faini, M., Gunsalus, R., Lostroh, P., Lupp, C., McCann, J., Millikan, D., chaefer, A., Stabb, E., Stevens, A., Visick, K., Whistler, C., and Greenberg, E.P. "Complete genome sequence of Vibrio fischeri: A symbiotic bacterium with pathogenic congeners." Proc. Natl. Acad. Sci. USA. In press (2005), published online 9 February 2005.

Stevens AM, Greenberg EP. “Quorum sensing in Vibrio fischeri: essential elements for activation of the luminescence genes.” J Bacteriol. 1997 Jan;179(2):557-62.

Edited by Maxine Mathew student of Rachel Larsen