2016-06-13
Abstract：
Riemerella anatipestifer is a well-described pathogen ofwaterfowl and other avian species that can cause septicemic and exudative diseases. In this study, we sequenced the complete genome ofR. anatipestifer strain Yb2 and analyzed it against the published genomic sequences ofR. anatipestifer strains DSM15868, RA-GD, RA-CH-1, and RA-CH-2. The Yb2 genome contains one circular chromosome of2,184,066 bp with a 35.73% GC content and no plasmid. The genome has 2,021 open reading frames that occupy 90.88% ofthe genome. A comparative genomic analysis revealed that genome organization is highly conserved among R. anatipestifer strains, except for four inversions ofa sequence segment in Yb2. A phylogenetic analysis found that the closest neighbor ofYb2 is RA-GD. Furthermore, we constructed a library of3,175 mutants by random transposon mutagenesis, and 100 mutants exhibiting more than 100-fold-attenuated virulence were obtained by animal screening experiments. Southern blot analysis and genetic characterization ofthe mutants led to the identification of49 virulence genes. Ofthese, 25 encode cytoplasmic proteins, 6 encode cytoplasmic membrane proteins, 4 encode outer membrane proteins, and the subcellular localization of the remaining 14 gene products is unknown. The functional classification oforthologous-group clusters revealed that 16 genes are associated with metabolism, 6 are associated with cellular processing and signaling, and 4 are associated with information storage and processing. The functions ofthe other 23 genes are poorly characterized or unknown. This genome-wide study identified genes important to the virulence of R. anatipestifer.
