The As87_04050 Gene Is Involved In Bacterial Lipopolysaccharide Biosynthesis And Pathogenicity Of Riemerella Anatipestifer

Riemerella anatipestifer is reported worldwide as a cause of septicemic and exucitive diseases of domestic ducks. In this study, we identified a mutant strain RA2640 by Tn4351 transposon mutagenesis in which the AS87 04050 gene was inactivated by insertion of the transposon. Southern blot analysis indicated that only one insertion was found in the genome of the mutant strain RA2640. SDS-PAGE followed by silver staining showed that the lipopolysaccharide (LPS) pattern of mutant strain RA2640 was different from its wild-type strain Yb2, suggesting the LPS was defected. In addition, the phenotype of the mutant strain RA2640 was changed to roLigh-type, evident by altered colony morphology, autoaggregation ability and crystal violet staining characteristics. Bacterial LPS is a key factor in virulence as well as in both innate and acquired host responses to infection. The rough-type mutant strain RA2640 showed higher sensitivity to antibiotics, disinfectants and normal duck serum, and higher capability of adherence and invasion to Vero cells, compared to its wild type strain Yb2. Moreover, the mutant strain RA2640 lost the agglutination ability of its wild-type strain Yb2 to R. anatipestifer serotype 2 positive sera, suggesting that the 0-antigen is defected. Animal experiments indicated that the the mutant strain RA2640 was attenuated by more than 100,000-fold, compared to its wild-type strain Y132. suggested that the AS87_04050 gene in R. anatipestifer is associated with the LPS biosynthesis and bacterial pathogenicity.