Capsular Polysaccharide of Erysipelothrix rhusiopathiae, the Causative Agent of Swine Erysipelas, and Its Modification with Phosphorylcholine

Abstract

The capsule has been implicated in the virulence of the swine pathogen Erysipelothrix rhusiopathiae, a rod-shaped, intracellular Gram-positive bacterium that has a unique phylogenetic position in the phylum Firmicutes and is a close relative of Mollicutes (mycoplasma species). In this study, we analyzed the genetic locus and composition of the capsular polysaccharide (CPS) of the Fujisawa strain of E. rhusiopathiae. Genome analysis of the Fujisawa strain revealed that the genetic locus for capsular polysaccharide synthesis (cps) is located next to an lic operon, which is involved in the incorporation and expression of phosphorylcholine (PCho). Reverse transcription-PCR analysis showed that cps and lic are transcribed as a single mRNA, indicating that the loci form an operon. Using the cell surface antigen-specific monoclonal antibody (MAb) ER21 as a probe, the capsular materials were isolated from the Fujisawa strain by hot water extraction and treatment with DNase, RNase, pronase, and N-acetylmuramidase SG, followed by anion-exchange and gel filtration chromatography. The materials were then analyzed by high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The CPS of E. rhusiopathiae is heterogeneous and consists of the major monosaccharides galacturonic acid, galactose, mannose, glucose, arabinose, xylose, and N-acetylglucosamine and some minor monosaccharides containing ribose, rhamnose, and N-acetylgalactosamine. In addition, the capsule is modified by PCho, which comigrates with the capsular materials, as determined by Western immunoblotting, and colocalizes on the cell surface, as determined by immunogold electron microscopy. Virulence testing of PCho-defective mutants in mice demonstrated that PCho is critical for the virulence of this organism.

Gene Content and Diversity of the Loci Encoding Biosynthesis of Capsular Polysaccharides of the 15 Serovar Reference Strains of Haemophilus parasuis

“…Several polysaccharide modifications can be found in the structures that aid in this role, including sialyl groups and phosphorylcholine (25,(76)(77)(78). The presence of sialyl groups in the newly published structures may be an important factor for virulence of this bacterium, as has been suggested for H. parasuis and shown in H. influenzae (25,76,77).…”

Bacterial Genomics Reveal the Complex Epidemiology of an Emerging Pathogen in Arctic and Boreal Ungulates

“…It has been hypothesized that this ability to persist in the environment for extended periods, in addition to E. rhusiopathiae 's wide host range, are the most important factors facilitating its widespread distribution (Brooke and Riley, 1999). Several virulence factors have been demonstrated or suggested for this bacterium, including neuraminidase, surface protective antigen A and the capsular polysaccharide (Ogawa et al, 2011; Shi et al, 2012), the majority of which appear to be commonly present (Janßen et al, 2015). Isolates of E. rhusiopathiae sequenced to date fall into three distinct clades, all of which appear to have retained some degree of host generalism (Forde et al, 2016), suggesting that most strains can likely be transmitted between species.…”

Characterization and Identification of a Novel Candidate Vaccine Protein through Systematic Analysis of Extracellular Proteins of Erysipelothrix rhusiopathiae

“…E. rhusio-pathiae lacks many orthologous genes for the biosynthesis of wall teichoic acids (WTA) and LTA, as well as the dltABCD operon, which is responsible for the incorporation of D-alanine into WTA and LTA (2). Furthermore, recent analysis of the capsular polysaccharide of E. rhusiopathiae indicated that this bacterium indeed has a complex, heterogeneous capsule that is modified by phosphocholine (22). The same study also suggested that there could be some overlap between the biosynthesis pathways of capsular polysaccharides and other cell wall components, including WTA and/or LTA (22).…”

“…Furthermore, recent analysis of the capsular polysaccharide of E. rhusiopathiae indicated that this bacterium indeed has a complex, heterogeneous capsule that is modified by phosphocholine (22). The same study also suggested that there could be some overlap between the biosynthesis pathways of capsular polysaccharides and other cell wall components, including WTA and/or LTA (22). Thus, in addition to its unique phylogenetic position as a member of the Firmicutes, it appears that the cell wall structure of E. rhusiopathiae may also be unique among Grampositive bacteria.…”