ARS | Publication request: Chemotactic factors of Flavobacterium columnare to skin mucus of healthy channel catfish (Ictalurus punctatus)

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 30, 2010
Publication Date: August 2, 2010
Repository URL: http://hdl.handle.net/10113/55576
Citation: Klesius, P.H., Wei Pridgeon, Y., Aksoy, M. 2010. Chemotactic factors of Flavobacterium columnare to skin mucus of healthy channel catfish (Ictalurus punctatus). FEMS Microbiology Letters. 310:145-151.

Interpretive Summary: To understand the factors involved in chemotaxis of Flavobacterium columnare, the causing agent of columnaris disease, we exposed the bacteria to various treatments followed by analysis of its chemotactic activity to catfish skin mucus. When the bacteria were pretreated by sodium metaperiodate, a chemical that is capable of removing the capsule of the bacteria, the chemotactic activity of F. columnare was dramatically inhibited. When the bacteria were pretreated with D-mannose, D-glucose, or N-acteyl-D- glucosamine, the chemotactic activity of the bacteria were also significantly inhibited. However, when the bacteria were pretreated with D-fructose, L-fucose, D- glucosamine, D-galactosamine, D-surcose, or N-acetyl-D-galactosamine, the chemotactic activity of the bacteria was not affected. These results suggest that at least three carbohydrate-binding receptors (D-mannose, D-glucose and N-acteyl-D- glucosamine) associated with the capsule might be involved with the bacteria’s chemotactic responses to the skin mucus of channel catfish. We also found that the transcriptional level of a gliding motility gene, gldH, was significantly induced in the bacteria after exposing the bacteria to the catfish mucus for 5 min, suggesting gldH gene might play an important role in the chemotactic response to the catfish mucus.

Technical Abstract: To gain insight into chemotactic factors involved in chemotaxis, we exposed a virulent strain of Flavobacterium columnare to various treatments followed by analysis of its chemotactic activity. Chemotactic activity of F. columnare was significantly (p < 0.05) inhibited when cells were pretreated by sodium metaperiodate, with a major portion of the capsular layer surrounding the cells was removed. Pretreatment of F. columnare with D-mannose, D-glucose and N-acteyl-D- glucosamine significantly (p < 0.05) inhibited its chemotaxis activity, whereas pretreatment of cells with D-fructose, L-fucose, D- glucosamine, D-galactosamine, D-surcose and N-acetyl-D-galactosamine failed to inhibit its chemotactic activity. These results indicate that at least three carbohydrate-binding receptors (D-mannose, D-glucose and N-acteyl-D- glucosamine) associated with the capsule of F. columnare might be involved with the chemotactic responses to the skin mucus of channel catfish. Relative transcriptional levels of three gliding motility genes (gldB, gldC, gldH) of F. columnare compared to 16S rRNA following exposure of F. columnare to catfish skin mucus were evaluated by quantitative PCR. QPCR results revealed that the transcriptional level of gldH was significantly (p<0.001) upregulated at 5 min post exposure to the catfish mucus, suggesting gldH might play an important role in the chemotactic response to the catfish mucus.