Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2009
Publication Date: 8/21/2009
Publication URL: http://handle.nal.usda.gov/10113/55558
Citation: Evenhuis, J., Lapatra, S.E., Verner-Jefferys, D.W., Dalsgaard, I., Welch, T.J. 2009. Identification of flagellar motility genes in Yersinia ruckeri by transposon mutagenesis. Applied and Environmental Microbiology. 75(20):6630-6633. Interpretive Summary: Yersinia ruckeri infection in salmonid aquaculture has been successfully controlled by immersion vaccination for over two decades. However, recent outbreaks in vaccinated fish have occurred in the United Kingdom, Spain, and in the United States and have been associated with a new emerging biogroup of Y. ruckeri (biotype 2). Biotype 2 strains appear to be variants of Serovar I Y. ruckeri that lack both motility and secreted lipase activity. In this study we present the identification of a single genetic element in biotype 1 Y. ruckeri that is necessary for both flagellar motility and the production of secreted lipase activity thus showing an interdependence of these two functions. The gene identified, flhA, encodes a protein predicted to function in flagellar secretion and motility. We also demonstrated that loss of flhA gene function does not affect the ability of Y. ruckeri to cause disease and therefore motility and secreted lipase activity are not necessary for the disease process. These results demonstrate that a single genetic mutation in biotype 1 Y. ruckeri can result in the loss of both motility and lipase secretion and no loss in virulence towards rainbow trout.
Technical Abstract: Here we demonstrate that flagellar secretion is required for production of secreted lipase activity in the fish pathogen Yersinia ruckeri and that neither of these activities is necessary for virulence in rainbow trout. Our results suggest a possible molecular mechanism for the emergence of non-motile biotype 2 Y. ruckeri.