Disruption of the M949_RS01915 gene changed the bacterial lipopolysaccharide pattern, pathogenicity and gene expression of Riemerella anatipestifer

AbstractRiemerella anatipestifer is an important pathogen that causes septicemia anserum exsudativa in ducks. Lipopolysaccharide (LPS) is considered to be a major virulence factor ofR. anatipestifer. To identify genes involved in LPS biosynthesis, we screened a library of random Tn4351 transposon mutants using a monoclonal antibody againstR. anatipestifer serotype 1 LPS (anti-LPS MAb). A mutant strain RA1067 which lost the reactivity in an indirect ELISA was obtained. Southern blot and sequencing analyses indicated a single Tn4351 was inserted at 116  bp in theM949_RS01915 gene in the RA1067 chromosomal DNA. Silver staining and Western blot analyses indicated that the RA1067 LPS was defected compared to the wild-type strain CH3 LPS. The RA1067 displayed a significant decreased growth rate at the late stage of growth in TSB in comparison with CH3. In addition, RA1067 showed higher susceptibility to complement-dependent killing, more than 360-fold attenuated virulence based on the median lethal dose determination, increased bacterial adhesion and invasion capacities to Vero cells and significantly decreased blood bacterial loads in RA1067 infected ducks, when compared to the CH3. An animal experiment indicated that inactivated RA1067 cells was effective in cross-protecting of the ducks from challenging withR. anatipestifer strains WJ4 (serotype 1), Yb2 (serotype 2) and HXb2 (serotype 10), further confirming the alteration of the RA1067 antigenicity. Moreover, RNA-Seq analysis ...
Source: Veterinary Research - Category: Veterinary Research Source Type: research