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Research Project: Integrated Research to Improve On-Farm Animal Health in Salmonid Aquaculture

Location: Cool and Cold Water Aquaculture Research

Title: Assessment of genetic variation in the multigene frp locus of Flavobacterium psychrophilum

item Wiens, Gregory - Greg
item Osbourn, Keira

Submitted to: American Fishery Society (Fish Health Section) Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2019
Publication Date: 6/18/2019
Citation: Wiens, G.D., Osbourn, K.E. 2019. Assessment of genetic variation in the multigene frp locus of Flavobacterium psychrophilum [abstract]. In: American Fishery Society (Fish Health Section) Proceedings. Western Fish Disease Workshop held in Ogden, UT 17 June - 20 June, 2019.

Interpretive Summary:

Technical Abstract: The genome of Flavobacterium psychrophilum contains a cluster of tandem genes, each with a conserved 5' and 3' sequence but a variable number of internal ~69 nucleotide repeats. We previously designated these as Flavobacterium repeat protein (frp) genes. Each repeat encodes ~23 amino acids with sequence similarity to the leucine rich repeats found in the virulence protein BspA, produced by the periodontal pathogen Tannerella forsythia. In F. psychrophilum strain CSF259-93, the frp locus contains 19 genes and spans 21.5 kb of the genome. All genes are in the same transcriptional orientation and each gene contains between 3 and 11 copies of the repeat. Here we examined genetic variation within the frp locus using a PCR assay that simultaneously amplified across the repeats of each gene to produce a ladder of PCR products or “frp profile”. Over seven-hundred isolates of F. psychrophilum were typed using this assay. Most of the isolates were obtained from rainbow trout BCWD outbreaks distributed across fourteen US states. In total, over forty different frp profiles were detected by the PCR assay. However, two dominant frp profile types accounted for over 70% of the isolates genotyped. Depending on location, some bacterial cold water disease outbreaks exhibited one frp profile type while other sites exhibited mixed types. The number of different frp profiles was highest in Idaho but this was biased by the overrepresentation of isolates from this state. In conclusion, the frp locus is polymorphic and studies are ongoing to understand the role of these proteins in pathogenesis and rainbow trout disease resistance.