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Research Project: Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture

Location: Aquatic Animal Health Research

Title: Influence of native catfish mucus on Flavobacterium columnare growth and proteolytic activity

Author
item Shoemaker, Craig
item Lafrentz, Benjamin
item Peatman, Eric - Auburn University
item Beck, Benjamin

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2018
Publication Date: 6/11/2018
Citation: Shoemaker, C.A., LaFrentz, B.R., Peatman, E., Beck, B.H. 2018. Influence of native catfish mucus on Flavobacterium columnare growth and proteolytic activity. Journal of Fish Diseases. https://doi.org/10.111/jfd.12833.

Interpretive Summary: Flavobacterium columnare is an economically important type of bacteria that causes columnaris disease of farmed catfish in the USA and abroad. Skin mucus is known to be an important factor in the early stages of columnaris disease, however little is known about mucus composition in catfish and how columnaris bacteria respond to mucus. The objectives of this study were to 1) characterize the terminal glycosylation (sugar) pattern (TGP) of catfish mucus, 2) determine the growth of F. columnare in water containing catfish mucus, and 3) examine extracellular protease activity (enzymes involved in disease) of two F. columnare isolates differing in virulence. The sugars alpha-D-mannose/alpha-D-glucose were found to be predominant in mucus and may be important for bacterial binding to the fish. In multiple experiments, F. columnare replicated and survived for up to 3 months in water containing catfish mucus. Virulence studies demonstrated that isolate AL-02-36 was highly virulent in channel catfish fry (0.1g) with cumulative mortality of 90 -100% versus 60% for isolate ALG-00-530 using similar numbers of bacteria. The highly virulent isolate AL-02-36 showed a greater amount of protease activity following growth in mucus, which suggests that the presence of mucus may be an important virulence factor in columnaris disease.

Technical Abstract: Flavobacterium columnare causes columnaris disease of farmed and wild freshwater fish. Skin mucus is an important factor in early stages of columnaris pathogenesis, albeit little studied. Our objectives were to 1) characterize the terminal glycosylation pattern (TGP) of catfish mucus, 2) determine the growth of F. columnare in formulated water (FW) containing channel catfish (Ictalurus punctatus) or hybrid catfish (Ictalurus punctatus X I. furcatus) mucus, and 3) examine extracellular protease activity of two F. columnare isolates differing in virulence. The TGP of catfish mucus by lectin binding was: alpha-D-mannose/alpha-D-glucose > N-acetyl-beta-D-glucosamine > N-acetyl-beta D-glucosamine/N-acetylneuraminic acid > N-acetyl-D-galactosamine > alpha-D-galactose/N-acetyl-alpha-D-galactosamine > beta-D-galactose = alpha-L-fucose. Virulence studies demonstrated isolate AL-02-36 was highly virulent in channel catfish fry (0.1g) with cumulative mortality of 90 -100% versus 60% for isolate ALG-00-530 at equivalent doses (~3 X 106 CFU mL-1); a similar result was observed in larger (0.7g) catfish. In multiple experiments, F. columnare replicated (2-3 logs) and survived (28 days) in formulated water containing catfish mucus. Highly virulent isolate AL-02-36 possessed at least 2.5-5-fold higher protease activity following growth in mucus than the less virulent ALG-00-530. Flavobacterium columnare utilized catfish mucus as a nutrient source and mucus presence modulated extracellular protease production.