title: Identification of the lic1ABCD operon that controls the phase-variable expression of phosphorylcholine on lipopolysaccharide from Avibacterium paragallinarum.
abstract: Phosphorylcholine (ChoP) is an important virulence factor found on the surface of many mucosal pathogens and its expression enhances bacterial colonization on mucous membranes and reduces susceptibility to antimicrobial peptides. Whole-genome sequencing analyses showed that Avibacterium paragallinarum contained an operon with strong sequence similarity to the lic1ABCD operon from Haemophilus influenzae and the pcgDABC operon from Pasteurella multocida; both operons are involved in metabolism and addition of ChoP on bacterial lipopolysaccharide (LPS). Western immunoblot analysis with ChoP-specific monoclonal antibody showed that ChoP is present on LPS of Av. paragallinarum and the expression of ChoP is controlled by phase variation mediated by the number of 5'-CAAT-3' tetranucleotide tandem repeats within the coding region of the lic1A gene. The number of tetranucleotide repeats varied widely among strains, and variation in the number of repeats was observed following in vivo passage but not in vitro passage. Antimicrobial susceptibility assays showed that ChoP expression decreased susceptibility of Av. paragallinarum to chicken antimicrobial peptide fowlicidin-1. This is the first report showing that ChoP is present on LPS from Av. paragallinarum and that Av. paragallinarum contains a phase-variable gene. These results could be valuable for understanding the mechanism of pathogenicity of Av. paragallinarum.
authors: Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan.
authors: Y T
authors: YT
authors: Chiang
authors: J H
authors: JH
authors: Shien
authors: D H
authors: DH
authors: Tan
authors: M K
authors: MK
authors: Shieh
authors: C C
authors: CC
authors: Liu
authors: Y S
authors: YS
authors: Chen
authors: P C
authors: PC
authors: Chang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D001483:Base Sequence; D002645:Chickens; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D008070:Lipopolysaccharides / Q000378:metabolism*; D050296:Microbial Viability; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D015661:Pasteurellaceae / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D010767:Phosphorylcholine / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013047:Specific Pathogen-Free Organisms; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D004269:DNA, Bacterial; D008070:Lipopolysaccharides; D037521:Virulence Factors; D010767:Phosphorylcholine