Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 10, 2009
Publication Date: September 21, 2009
Citation: Lafrentz, B.R., Klesius, P.H., Shoemaker, C.A. 2009. Chemotactic response of Flavobacterium columnare to channel catfish mucus. In: Proceeding of the Members of the Genus Flavobacterium. Flavobacterium 2009, September 21-23, 2009, Paris, France. CDROM. Technical Abstract: Research has demonstrated that genomovar II Flavobacterium columnare isolates are more pathogenic for channel catfish (Ictalurus punctatus) and have a higher capacity for adhesion than genomovar I isolates. To begin to define the basis for this, the objectives of the present study were to determine whether there are differences in the chemotactic responses of genomovar I and II isolates to channel catfish mucus and to develop an improved method to characterize these responses. Mucus from the skin of channel catfish was collected and representative genomovar I and II F. columnare isolates were assayed for chemotactic responses to mucus using a capillary tube method. The results demonstrated that genomovar II isolates exhibited higher relative chemotactic indices compared to genomovar I isolates and the motility of the isolates did not appear to be involved in these responses. The chemotactic response of a genomovar II isolate to individual mucus samples was examined and the results demonstrated variable responses of the bacterium to these samples. This suggests that there are differences in the concentration of chemoattractant(s) in mucus samples from individual fish. A culture independent method was developed to further characterize the chemotactic response of F. columnare. The method employs the use of blind-well chemotaxis chambers and uses a cell proliferation assay to quantify viable cells. The improved method overcomes the difficulties associated with the traditional capillary tube assay and reduces the time and labor associated with culturing the bacterium. Application of the method to two sets of channel catfish mucus confirmed the variation observed in the chemotactic response of F. columnare to individual catfish mucus samples, and the results were comparable to the capillary tube method. These studies suggest that the chemotactic response of F. columnare is important for pathogenesis and further characterization of these responses will increase the understanding of this host-pathogen interaction.