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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetics, Physiology, and Health Research to Improve Catfish Production

Location: Warmwater Aquaculture Research Unit

Title: What is a species a species? Genetic variability of Edwardsiella tarda in the Southeastern United States

item Griffin, Matt -
item Quiniou, Sylvie
item Cody, Theresa -
item Tabuchi, Maki -
item Ware, Cynthia -
item Cipriano, Rocco -
item Michael, Mauel -
item Esteban, Soto -

Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: April 6, 2013
Publication Date: April 29, 2013
Citation: Griffin, M., Quiniou, S., Cody, T., Tabuchi, M., Ware, C., Cipriano, R., Michael, M., Esteban, S. 2013. What is a species a species? Genetic variability of Edwardsiella tarda in the Southeastern United States. Annual Eastern Fish Health Workshop. P.38.

Technical Abstract: The intra-specific variability of Edwardsiella tarda isolates from fish in the eastern United States was assessed. Repetitive sequence mediated PCR (rep-PCR) and multi-locus sequence analysis identified two distinct genotypes (DNA group I; DNA group II). This was supported by fluorometric estimation of G+C content, which demonstrated nearly a 4% difference between groups. Isolates that fell into DNA group II demonstrated more similarity to E. ictaluri than DNA group I, which contained the reference E. tarda strain (ATCC #15947). PCR analysis using published E. tarda-specific primer sets yielded variable results, with some primer sets failing to amplify target DNA from several isolates. These isolates were indistinguishable by conventional techniques, with all isolates demonstrating phenotypic characteristics consistent with E. tarda. Analysis using commercial test kits identified multiple phenotypes, although no metabolic characteristic could reliably discriminate between genetic groups. Anti-microbial and fatty acid profiles did not demonstrate remarkable differences between groups. However, the significant genetic variation between these groups suggests organisms from DNA group II represent an unrecognized, genetically distinct taxa of Edwardsiella that is phenotypically indistinguishable from E. tarda.

Last Modified: 7/27/2016
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