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

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 (a) characterize the terminal glycosylation pattern (TGP) of catfish mucus, (b) determine the growth of F. columnare in formulated water (FW)-containing channel catfish (Ictalurus punctatus) or hybrid catfish (Ictalurus punctatus X Ictalurus furcatus) mucus and (c) examine extracellular protease activity of two F. columnare isolates differing in virulence. The TGP of catfish mucus by lectin binding was as follows: 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 (0.1 g) with cumulative mortality of 90%-100% versus 60% for isolate ALG-00-530 at equivalent doses (~3 × 10 CFU/ml); a similar result was observed in larger (0.7 g) 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- to fivefold 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.

The role of rpoS in the regulation of Vibrio alginolyticus virulence and the response to diverse stresses

“…Adhesion of the pathogen to the host surface constitutes a critical step in infection initiation (Chen et al., ; Shoemaker, LaFrentz, Peatman, & Beck, ), and multiple pathogenic bacteria show strong adhesion abilities (Lin et al., ; Papadopoulou, Dalsgaard, Lindén, & Wiklund, ; Qin, Lin, Chen, Xu, & Yan, ). Bacterial adhesion is regulated by different genes (Guo et al., ; Huang, Qin, et al., ; Jiang et al., ; Xu, Huang, Su, & Yan, ).…”

Vertebrate mucus stimulates biofilm development and upregulates iron acquisition genes in Flavobacterium columnare

“…It was initially determined that channel catfish mucus could support the growth of F. columnare in broth cultures independent of traditional F. columnare growth medium. Previous work had demonstrated that tilapia and pig mucus could be used to sustain F. columnare over several weeks in broth cultures (Shoemaker & Lafrentz, ), and more recently, hybrid catfish mucus was used to demonstrate a similar outcome (Shoemaker et al, ). In both studies, it had been concluded that both tilapia and pig mucus had a nutritional benefit, which could be utilized by the bacterial cells in the broth culture.…”

“…We observed significant biofilm growth at 5 µg/ml with LSU-066-04 and 94-081 ( Figure 4b The genomovar I isolates were again less responsive: 0901393 demonstrated significantly more biofilm growth at 40 µg/ml (p < .05; Figure 4d) and highly significant biofilm growth at 60 µg/ml (p < .0001); and CDI-A only demonstrated significantly more biofilm growth at 60 µg/ml (p < .05; Figure 4e). (Shoemaker & Lafrentz, 2015b), and more recently, hybrid catfish mucus was used to demonstrate a similar outcome (Shoemaker et al, 2018). In both studies, it had been concluded that both tilapia and pig mucus had a nutritional benefit, which could be utilized by the bacterial cells in the broth culture.…”

“…within the mucus may be or which receptor it is binding on the surface of planktonic cells, which leads to the activation of the biofilm phenotype (Lange et al, 2018;O'Toole et al, 1999). Recent work sought to identify the terminal glycosylation patterns of mucus derived from hybrid catfish and describe the growth characteristics of different F. columnare isolates in formulated water supplemented with hybrid catfish mucus (Shoemaker et al, 2018). signalling, which could potentially be a way in which F. columnare initiates biofilms (Chen & Xie, 2011;Tsai & Winans, 2010).…”

“…Fish mucus is an important defence against bacterial pathogens, and the mucosal layer offers protection against the surrounding aquatic environment (Ben Hamed et al, 2018;Benhamed, Guardiola, Mars, & Esteban, 2014). Interestingly, it has also been shown that fish mucus may act as a nutritive source for F. columnare in broth cultures (Shoemaker & Lafrentz, 2015a;Shoemaker, LaFrentz, Peatman, & Beck, 2018), and F. columnare planktonic cells have also been established as chemotactic to fish mucus (Klesius, Shoemaker, & Evans, 2008;Lafrentz & Klesius, 2009). Others have also shown the chemotactic effect of other Gram-negative pathogens to fish intestinal mucus and other animal sources (O'Toole et al, 1999;O'Toole, Milton, & Wolf-Watz, 1996).…”