Characterization of a novel Yersinia ruckeri serotype O1-specific bacteriophage with virulence neutralizing activity

Authors: Welch, Timothy - Tim

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2019
Publication Date: 12/11/2019
Citation: Welch, T.J. 2019. Characterization of a novel Yersinia ruckeri serotype O1-specific bacteriophage with virulence neutralizing activity. Journal of Fish Diseases. 43(2):285-293. https://doi.org/10.1111/jfd.13124.
DOI: https://doi.org/10.1111/jfd.13124

Interpretive Summary: Bacteriophage (or phage) are viruses that infect and kill bacteria. Phage have long been considered excellent candidates to treat or prevent bacterial disease in humans and animals and could be safe alternatives to traditional antibiotics. In this study, we present the identification and characterization of a phage (fNC10) that attacks and kills the most problematic strains of the rainbow trout pathogen Yersinia ruckeri. We show that fNC10 recognizes Y. ruckeri through binding to lipopolysaccharide, a large carbohydrate structure that covers the surface of bacteria and provides protection from the host immune system. We also demonstrate that purified fNC10 contains a unique activity capable of degrading lipopolysaccharide and in doing so neutralizing the ability of this bacterium to cause disease. These data demonstrate a potential utility of fNC10 and its associated lipopolysaccharide degrading activity for Y. ruckeri disease control in aquaculture.

Technical Abstract: A lytic bacteriophage (fNC10) specific to serotype O1 Y. ruckeri has been identified and evaluated to assess the potential use of bacteriophages and their products for disease control in aquaculture. Electron microscopy of purified fNC10 revealed a virion particle with a small (70 nm) polyhedral head and short tail. fNC10 infected only serotype O1 strains of Y. ruckeri and failed to bind a defined Y. ruckeri mutant strain lacking O1 lipopolysaccharides (O1-LPS) suggesting that fNC10 uses O1-LPS as its receptor. In addition, spontaneous fNC10-resistant mutants of Y. ruckeri displayed defects in O1-LPS production and were sensitive to rainbow trout serum. Purified fNC10 displayed a polysaccharide depolymerase activity capable of degrading Y. ruckeri O1-LPS and thereby sensitizing Y. ruckeri to the bactericidal effects of rainbow trout serum. The fNC10-asociated polysaccharide depolymerase activity also reduced the ability of Y. ruckeri cells to cause mortality following intraperitoneal injection into rainbow trout. These data demonstrate a potential utility of fNC10 and its associated polysaccharide depolymerase activity for Y. ruckeri disease prevention.