Characterization and Biological Role of the O-Polysaccharide Gene Cluster ofYersinia enterocoliticaSerotype O:9

Abstract

Yersinia enterocolitica serotype O:9 is a gram-negative enteropathogen that infects animals and humans. The role of lipopolysaccharide (LPS) in Y. enterocolitica O:9 pathogenesis, however, remains unclear. The O:9 LPS consists of lipid A to which is linked the inner core oligosaccharide, serving as an attachment site for both the outer core (OC) hexasaccharide and the O-polysaccharide (OPS; a homopolymer of N-formylperosamine). In this work, we cloned the OPS gene cluster of O:9 and identified 12 genes organized into four operons upstream of the gnd gene. Ten genes were predicted to encode glycosyltransferases, the ATP-binding cassette polysaccharide translocators, or enzymes required for the biosynthesis of GDP-N-formylperosamine. The two remaining genes within the OPS gene cluster, galF and galU, were not ascribed a clear function in OPS biosynthesis; however, the latter gene appeared to be essential for O:9. The biological functions of O:9 OPS and OC were studied using isogenic mutants lacking one or both of these LPS parts. We showed that OPS and OC confer resistance to human complement and polymyxin B; the OPS effect on polymyxin B resistance could be observed only in the absence of OC.Yersinia enterocolitica serotypes O:3, O:5,27, O:8, and O:9 include strains that infect both humans and animals (16). Pathogenesis of these strains is associated with the presence of common virulence factors encoded on the chromosome and on pYV, the Yersinia virulence plasmid (73). Despite the genetic and phenotypic similarity, however, the serotypes display epidemiological and host range differences (17,22). Biotyping and serotyping based on the antigenic O-polysaccharide (OPS or O-antigen) are important in studying Y. enterocolitica infections. OPS is a distal part of lipopolysaccharide (LPS), which is the major component of the outer membrane of gram-negative bacteria (55,63). In addition to OPS, LPS comprises lipid A, a hydrophobic membrane anchor, and a core oligosaccharide, divided into a lipid A-proximal inner core and an outer core (OC). The latter typically provides the attachment site for the polymeric OPS (55). Heteropolymeric OPSs, such as that of Y. enterocolitica serotype O:8 (63), are the most frequent among gram-negative bacteria; they are made up of identical oligosaccharide repeat units comprising three to eight different monosaccharides (55). Y. enterocolitica serotypes O:3 and O:9, however, display a homopolymeric OPS composed of singlesugar repeating units of 6-deoxy-L-altrose or N-formylperosamine, respectively (24, 41). Furthermore, the structures of the O:3 and O:9 core oligosaccharides are identical (51, 63). They both have a branching hexasaccharide termed OC which in genetic and biosynthetic terms resembles more closely a nonpolymerized O unit than the classical hexose-containing OC of Escherichia coli or Salmonella species (67, 68). The linkage of both the OC and the homopolymeric OPS to the inner core is a unique feature shared between serotypes O:3 and O:9. The O:9 OPS is identical to that of Bru...

Evolutionary Dynamics of the Yersinia enterocolitica Complex

“…Both BT 2 O:9 and BT 3 O:9 clusters are identical and are the same O:9 operons described in the past (Skurnik, et al, 2007). There are six CDSs involved in sugar biosynthesis (manCB, gmd, per, wbcTV The exact serotype of the reference BT 5 isolate is unknown, but the serotype typically described for this biotype is often a mixture of O-antigens 2a, 2b, and 3 (Bottone, 1997;Bottone, 1999;Bartling, et al, 2004).…”

“…The location of the O-antigen clusters for O:3 and O:9 was unknown, although their operon structure has been investigated in the past (Reeves, et al, 1996b;Skurnik and Bengoechea, 2003;Skurnik, et al, 2007). The O-antigen clusters for O:3 and O:9 are found in the same genomic location between a putative membrane protein (YE2779) and gnd, a phosphogluconate dehydrogenase (YE2773, Figure 4.13).…”

“…The lipopolysaccharide (LPS) of Y. enterocolitica has been proposed as a supporting virulence factor as it confers resistance to polymyxin and antimicrobial peptides and has been associated with virulence in the mouse model (Zhang, et al, 1997;Skurnik, et al, 1999;Skurnik, et al, 2007) (Zhang, et al, 1997). In O:3 and O:9 O-antigens the chain consists of unbranched homopolymers (Zhang, Toivanen and Skurnik, 1996;Skurnik and Bengoechea, 2003).…”

Enterobacterial common antigen and O-specific polysaccharide coexist in the lipopolysaccharide of Yersinia enterocolitica serotype O : 3

“…enterocolitica O : 3 and O : 9 share many similarities in that the LA-IC moiety in both serotypes can be substituted by either OC or homopolymeric OPS (Skurnik et al, 2007). It was interesting to know whether ECA and OPS coexistence is shared among structurally similar serotypes or whether it is serotype specific.…”

The mechanisms of complement activation in normal bovine serum and normal horse serum against Yersinia enterocolitica O:9 strains with different outer membrane proteins content

“…Ra-Rd mutants in bacteria, which are defective in the biosynthesis of the O-specific chain or mutants defective in the biosynthesis of a complete core in LPS, activate the complement through the alternative pathway (Różalski 1995, Taylor 1995. Skurnik et al (2007) suggest that LPS in the Y. enterocolitica O:9 serotype plays a role in assisting and strengthening the mainly YadA-dependent resistance to human complement action. Their results confirmed higher survival rate of the strains lacking the O-antigen in human serum with the inhibited classical route, which suggests that the O-antigen of the Y. enterocolitica O:9 serotype activates the antibody-dependent pathways of human complement (Skurnik et al 2007).…”