Plesiomonas shigelloides

Classification

Bacteria; Proteobacteria; Gamma Proteobacteria; Enterobacteriales; Enterobacteriaceae

Species

NCBI: Taxonomy

Plesiomonas shigelloides

Description and Significance

Describe the appearance, habitat, etc. of the organism, and why you think it is important.

Plesiomonas shigelloides is a facultatively anaerobic chemo-organotrophic Gram-negative bacterium. Being that this organism is faculatively anaerobic means that it can use oxygen as a terminal electron acceptor when it is present, but also flawlessly switches to fermentation as a means of producing ATP when oxygen is absent. One study has shown that like many organisms, Plesiomonas shigelloides utilizes glucose as a source of carbon as well as energy source. However, what is somewhat odd, is that these particular organisms have a membrane bound mannose permease. It is unknown as to why this organism has the ability to take in mannose, but lacks the ability to use it constructively as a carbon or energy source. The lack of mannose isomerase (coverts mannose to its 2 epimer glucose) causes a build up of mannose 6-phosphate and subsequent death.

Genome Structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?

Cell Structure, Metabolism and Life Cycle

Interesting features of cell structure; how it gains energy; what important molecules it produces.

It is a short gram-negative rod. It is oxidase-positive and catalase-positive. The organism moves by polar flagella which are lophotrichous, meaning they have multiple flagella in the same area. Because of this, the bacteria can only move in one direction. (Adams and Moss)

Ecology and Pathogenesis

Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Plesiomonas shigelloides is an organism that is commonly found in fresh and brackish water (brackish water meaning water that has a noticeable amount of salinity but less than salt water or ocean water). This ubiquitous bacteria is commonly found living cold-blooded animals such as snakes, frogs, turtles and fish. It has also been found, less frequently, in cattle, poultry, pigs, sheep, cats and dogs. All of these host/inhabitant relationships are said to be a form of commensalism. This bacteria is said to thrive in warmer aquatic environments of temperatures of 35-38 degrees Celcius. The ways in which Plesiomonas shigelloides gains energy by the fermentation of sugars with little or no gas production. An interesting controversy surrounds this organism. This controversy is based around the assumption whether or not Plesiomonas shigelloides is harmful to human hosts. This controversy stems from inconclusive results regarding many outbreaks of gastroenteritis and diarrhea around the globe. It is debatable whether this bacteria is an opportunistic pathogen, meaning that it will not cause ailments upon entry of health humans (pathogenesis occurs only in immunosuppresed individuals), or simply a non-pathogenic symbiont. If this organism is pathogenic, then it most likely produces an enterotoxin, which passes into the intestinal tract causing diarrhea (one study says it produces a cholera-like enterotoxin). Symptoms normally last only 1~7 days in patients. Eating raw oysters seems to be the most common form of Plesiomonas shigelloides incorporation to one’s system.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

D. P. Henderson, Wyckoff, E.E., Rashidi, C. E., Verlei, H. and Oldham A. L. Characterization of the Plesiomonas shigelloides Genes Encoding the Heme Iron Utilization System. Journal of Bacteriology, May 2001, p. 2715-2723, Vol. 183, No. 9

A. Salerno, Delétoile, A., Lefevre, M., Ciznar, I., Krovacek, K., Grimont, P., and Brisse, S. Recombining Population Structure of Plesiomonas shigelloides (Enterobacteriaceae) Revealed by Multilocus Sequence Typing. Journal of Bacteriology, November 2007, p. 7808-7818, Vol. 189, No. 21

M.R. Adams and Moss, M.O. Food Microbiology. Third Edition. RSC Publishing. Cambridge. 2008. p 234-235.

Author

Page authored by Alex Ernst and Amanda Feighner, student of Prof. Jay Lennon at Michigan State University.

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