Edwardsiella tarda
A Microbial Biorealm page on the genus Edwardsiella tarda
Classification
Higher order taxa
Bacteria, Proteobacteria, Gamma proteobacteria, Enterobacteriales, Enterobacteriaceae
Species
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NCBI: Taxonomy |
Edwardsiella tarda
Description and significance
Edwardsiella tarda was the first species identified of the genus Edwardsiella, and was named after a renowned microbiologist P. R. Edwards (Janda, 1991). E. tarda was originally named Edwardsiella anguilimortifera, but it was ultimately changed to E. tarda because this name was used more often in scientific reports. E. tarda is a Gram-negative bacilli that belongs to the Enterobacteriaceae family and was first characterized in 1965 (Health, 2001). E. tarda has many traits that are characteristic of many enterobacteria such as E. coli. These characteristics include it being a facultative anaerobe, rod-shaped, and motile (Health 2001). Its motility is due to peritrichous flagella. Although Edwardsiella tarda was initially characterized more than thirty years ago, there is still very little known about this bacterium. E. tarda is known for causing diseases in both humans and fish, both of which can potentially be fatal if untreated. Though this may be the case, the likelihood of a serious infection is very slim. As a fish pathogen, it is of particular importance to aquaculture and the fishing industry, especially commercial fish farms. It may become more of a significant health issue to fish and humans alike, especially in light of emerging and increasing antibiotic resistance in fish pathogens, due in large part to overuse of antibiotics in fish farming (Greenlees et al., 1998; Lehane and Rawlin, 2000). Some studies have focused on using proteomics and molecular techniques to elucidate the mechanism of pathogenesis in Edwardsiella tarda (Rao et al., 2004). Studies such as these have allowed the characterization of novel toxin secretion pathways, such as the discovery of a type VI secretion system essential for E. tarda pathogenesis (Zheng and Leung, 2007). These types of analyses help us better understand bacterial pathogenesis in general, as well as provide new insights for fighting disease.
Genome structure
There are two genomes for strains of E. tarda in progress (documented in NCBI): strains ATCC 23685 and EIB 202 (Du, 2007). ATCC 23685 is a strain commonly found in normal human gut flora, while EIB 202 is a virulent strain that causes disease in many fresh water and marine fish (Du, 2007).
Cell structure and metabolism
E. tarda is a Gram-negative bacilli. E. tarda has many traits that are characteristic of many enterobacteria such as E. coli. These characteristics include it being a facultative anaerobe, rod-shaped, and motile (Health 2001). Its motility is due to peritrichous flagella. It is positive for glucose fermentation, but negative for lactose fermentation and is unable to grow on D-mannitol or D-sorbitol. E. tarda is also oxidase-negative and catalase-positive. It does not produce ureasebut is similar to salmonella in that it is able to generate hydrogen sulfide on laboratory media.
Ecology
Edwardsiella tarda is predominantly found in freshwater environments colonizing the guts of fish, including flounder living off the coasts of East Asia and catfish that live in regions of the United States. It can also be found in the intestinal tract of birds, reptiles, and mammals (Janda et. al, 1991). THey can be found as part of the human intestinal flora as well, although this seems to be rare, and is usually due to an infection or prolonged contact with contaminated water. Other factors that increase the risk of getting an infection include high iron concentration, very young or old age, or an immune incompetence.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Current Research
Enter summarries of the most rescent research here--at least three required
References
Edited by student of Dr. Maia Larios-Sanz at University of St. Thomas
