Characterization of a bacteriophage LPS depolymerase: potential role in disease control

Authors: Welch, Timothy - Tim

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/26/2008
Publication Date: 7/26/2008
Citation: Welch, T.J. 2008. Characterization of a bacteriophage LPS depolymerase: potential role in disease control. Meeting Abstract. Edinburgh International Phage Conference. Paper No. 105.

Interpretive Summary:

Technical Abstract: Yersinia ruckeri is a gram negative bacterium that causes Enteric Redmouth Disease, an acute hemorrhagic septicemia affecting cultured salmonid fish species. A lytic bacteriophage (NC10) with a host range specific to Y. ruckeri has been identified and is being used as a model to assess the potential use of phage and their products for disease control in aquaculture. In this study, purified phage NC10 was shown to display a unique phage particle-associated polysaccharide depolymerase activity capable of degrading the Y. ruckeri O1-polysaccharide polymer (located in the extracellular matrix). Since intact high-molecular-weight lipopolysaccharides (LPS) often protect invasive pathogens from the bactericidal effects of serum, it is possible that phage NC10-mediated degradation of LPS could sensitize Y. ruckeri to fish serum. To test this, purified phage were UV treated such that they could no longer replicate but retained their phage particle-associated polysaccharide depolymerase activity. Y. ruckeri cells grown in trout serum with UV inactivated phage caused a several log drop in viability over the course of 2.5 hours while cells grown in heat-inactivated sera were unaffected by phage treatment. Furthermore, Y. ruckeri treated with UV inactivated phage were also dramatically reduced in their ability to cause mortality following intraperitoneal injection into rainbow trout. Spontaneous mutant derivatives of phage NC10 were identified which produce reduced polysaccharide depolymerase activity. Genomic and functional-genetic analysis of mutant and wildtype NC10 phage showed that a virion protein (gp69) is essential for this polysaccharide depolymerase activity. Gp69 encodes a predicted protein of 982 amino acids with weak homology to a portion of Endo-N, a phage protein necessary for hydrolyzing the E.coli K1 polysaccharide capsule. These data demonstrate a potential utility of the NC10 phage and its associated polysaccharide depolymerase activity for Y. ruckeri disease prevention in aquaculture.