Identification of thelic1ABCDoperon that controls the phase-variable expression of phosphorylcholine on lipopolysaccharide fromAvibacterium 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.

Comparison of RP‐HPLC modes to analyse the N‐glycome of the free‐living nematode Pristionchus pacificus

“…Another unusual aspect of nematode glycans is the presence of phosphorylcholine; this zwitterionic modification is otherwise known from some bacterial lipopolysaccharides, fungal cell walls and one cestode glycoprotein (Ag5 from Echinococcus granulosus ) (20-22). The phosphorylcholine attached to the N-glycans of one nematode glycoprotein (ES-62 from Acanthocheilonema viteae ) is apparently necessary for the immunomodulatory activity of this protein (23); on the other hand, a possibly contradictory aspect is that phosphorylcholine is recognised by mammalian C-reactive protein (24), a pentraxin whose levels in the serum increases during inflammation.…”

Analysis of Bacterial Phosphorylcholine-Related Genes Reveals an Association between Type-Specific Biosynthesis Pathways and Biomolecules Targeted for Phosphorylcholine Modification

“…2 . Moreover, the LicA, -B, -C, and -D homologs in H. haemolyticus ( 31 ), Histophilus somni ( 32 ), S. pneumoniae ( 16 , 33 ), Streptococcus oralis ( 34 ), Streptococcus mitis ( 35 ), Pasteurella multocida ( 36 ), commensal Neisseria species ( 3 ), Avibacterium paragallinarum ( 37 ), Erysipelothrix rhusiopathiae ( 38 ), and Mycoplasma fermentans ( 39 – 41 ) have previously been shown to mediate the synthesis of glycoconjugates, such as WTA-, LTA-, and LOS-ChoP structures. In this study, we have identified for the first time the presence of the Lic-1 locus in Proteus mirabilis ( 42 ) and Morganella morganii ( 43 ), both of which express ChoP-modified glycan structures.…”