Virulent and nonvirulent Flavobacterium columnare colony morphologies: characterization of chondroitin AC lyase activity and adhesion to polystyrene

Abstract

Aims: Colony morphology variants of fish pathogenic Flavobacterium columnare were studied to clarify the role of colony morphology change in the virulence of the bacterium. Typical rhizoid colony (Rz) variants are virulent and moderately adherent, nonrhizoid rough (R) colony variants are nonvirulent and highly adherent, and soft colony (S) variants are nonvirulent and poorly adherent. Methods and Results: Chondroitin AC lyase activity, adhesion to polystyrene at different temperatures and after modification of bacterial surface, and lipopolysaccharide (LPS) profiles of the variants were studied. The chondroitinase activity was significantly higher in the virulent, rhizoid variants than in the rough variants of the same strain. Temperature significantly increased the adhesion of rhizoid variants up to 20°C. Modification of bacterial surface suggested that adhesion molecules contain both carbohydrates and proteins. LPS did not differ between the variants of the same strain. Conclusions: The results suggest that in Fl. columnare both rhizoid colony morphology and high chondroitinase activity are needed for virulence and that temperature may promote the adhesion of the virulent variants to surfaces at fish farms. Significance and Impact of the Study: New information is produced on the virulence mechanisms of Fl. columnare and the reasons behind the survival of the bacterium at fish farms.

Biofilm Formation by the Fish Pathogen Flavobacterium columnare: Development and Parameters Affecting Surface Attachment

“…Because of the protective function of biofilm, it is possible that biofilm formation enhances the potential of these bacteria to survive in the aquatic environment. Kunttu et al (37) found that adhesion was significantly enhanced when the temperature increased from 5 to 15 to 20°C but then decreased at 25°C. In our study, we also found that growth was influenced by temperature.…”

Effect of physiochemical factors on autoaggregation and adhesion of Flavobacterium johnsoniae-like isolates

“…Kunttu et al (2011) observed significant reduction in adhesion of all F. columnare morphology variants, except for one rough colony variant following proteinase K treatment. In the present study, F. johnsoniae-like isolates demonstrated decreased adhesion following proteinase K treatment, while autoaggregation indices increased significantly.…”

“…Rickard et al (2000) observed that coaggregation among five aquatic bacteria was mediated by varying lectin-saccharide interactions, since aquatic strains may carry multiple adhesins or receptors or a combination of both on their surfaces. This might be true for members of the genus Flavobacterium, given the diversity of responses observed following anti-adhesion treatments, with adhesion molecules containing both carbohydrate and protein moieties (Kunttu et al, 2011). Flavobacteria might also utilize a "switch on-off" mechanism which involves environmental control of adhesins or receptors associated with the bacterial surface in direct relation to nutri-tional and possibly quorum-sensing cues.…”

“…Treatment with SMP, an oxidizing agent which cleaves the C-C bond between vicinal hydroxyl groups, caused a significant reduction in F. columnare adhesion (Decostere et al, 1999;Kunttu et al, 2011) and hemagglutination (Decostere et al, 1999) by eliminating the lectin and abolishing adhesion. F. columnare chemotaxis, which is correlated with its virulence, was also inhibited by SMP pre-treatment (Klesius et al, 2010).…”

Complete genome sequence analysis of the fish pathogen Flavobacterium columnare provides insights into antibiotic resistance and pathogenicity related genes

“…Chondroitin AC lyase (chondroitinase, Pf1_01408) may cause the necrotic lesions by degrading chondroitin in the extracellular matrix of fish tissue [46]. The F. columnare isolates from cold water exhibited significantly greater chondroitinase activity than isolates from warm water, suggested that chondroitinase activity may be correlated with virulence [47,48]. Internalin A (InlA, Pf1_01412) is a surface protein used by the bacteria to invade host cells via cadherins transmembrane proteins [49].…”