Title: Analysis of the Flavobacterium columnare transcriptome reveals gene expression signatures mediating virulence Authors
Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: October 25, 2013
Publication Date: N/A
Technical Abstract: Flavobacterium columnare, the causative agent of columnaris disease causes substantial mortality worldwide in numerous freshwater cultured fish species. Despite its importance, a broader understanding of the genes and their protein products that mediate virulence is urgently needed. Therefore, in the present study, using the next generation sequencing approach RNA-seq, we characterized the basal and post-activational gene expression profiles exhibited between two F. columnare isolates with markedly different levels of virulence. First, we demonstrated virulence differences between the two isolates of F. columnare. In a laboratory challenge, we found that significantly greater mortality (P<0.001) was observed in fingerling channel catfish challenged with isolate LSU-066-04 than fish challenged with isolate LV-359-01. Over the course of the 7 day study period, mortality was 100% in LSU-066-04 challenged fish with all fish dying within the first 24 h. In stark contrast, mortality in the LV-359-01-challenged group was substantially lower with 26.7% of fish dying on days 1-4 post-challenge. Intriguingly, there were no differences in initial adhesion between the isolates at 1 h and 2 h post-challenge; however, significantly more F. columnare cells were present on the gill after 4 h in LSU-066-04 challenged fish. Next, in an in vitro study, we applied RNA-seq to the two isolates after a 4 h incubation in well water (termed unactivated) or with channel catfish gill homogenate (activated). The results revealed numerous and large-scale differences in gene expression between the two isolates in both the unactivated and activated treatments. Notable differences included the changes in expression of genes related to inorganic ion transport and metabolism, energy production/conversion, and proteolytic enzymes linked to tissue degradation. Our findings provide novel insights connecting differential gene expression signatures with pathogen virulence and offer promising new targets for disease prevention and treatment.