Sebastian Noskowiak Biology
David Hunnicutt Doctor
Flavobacterium columnare is a rod-shaped gram negative bacterium that is strictly aerobic. It is the causative agent of columnaris disease (CD) in many cultured fish, including salmonids, in both warm and cold-water systems. Presentation of CD consists of “straw-like” colony growths on mucosal surfaces of fish (gills and scales) which negatively impacts both fish health and the aquaculture industry. The Type IX Secretion System (T9SS) is necessary for F. columnare virulence. Among the genes that are important for T9SS function is gldN, which is required for both secretion and motility in F. columnare. Deletion of the gldN gene has been shown to reduce virulence. The goal of this study is to examine the toxicity of secreted proteins from the T9SS. Zebrafish infection trials and spent media toxicity assays were performed to examine the effect of spent media (secreted proteins from F. columnare) from the wild type (MSFC-4) and strains with knockouts in the the genes gldN and cylB. CylB is believed to be secreted from through the T9SS. Results suggest the strains lacking specific proteins responsible for chemical reactions that create cyclic compounds appear to cause reduced virulence. Continued experimentation with F. columnare strains and virulence testing in our zebrafish model should shed more light on the mechanisms by which F. columnare causes disease in fish and may lead to the identification of more effective vaccine candidates.