The structure of the O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O36 containing 3-deoxy-d-manno-oct-2-ulosonic acid

O-antigens of bacteria of the genus providencia: structure, serology, genetics, and biosynthesis

The genus Providencia consists of eight species of opportunistic pathogenic enterobacteria that can cause enteric diseases and urinary tract infections. The existing combined serological classification scheme of three species, P. alcalifaciens, P. stuartii, and P. rustigianii, is based on the specificity of O-antigens (O-polysaccharides) and comprises 63 O-serogroups. Differences between serogroups are related to polymorphism at a specific genome locus, the O-antigen gene cluster, responsible for O-antigen biosynthesis. This review presents data on structures of 36 O-antigens of Providencia, many of which contain unusual monosaccharides and non-carbohydrate components. The structural data correlate with the immunospecificity of the O-antigens and enable substantiation on a molecular level of serological relationships within the genus Providencia and between strains of Providencia and bacteria of the genera Proteus, Escherichia, and Salmonella. Peculiar features of the O-antigen gene cluster organization in 10 Providencia serogroups and biosynthetic pathways of nucleotide precursors of specific monosaccharide components of the O-antigens also are discussed.

Structural, serological, and genetic characterization of the O-antigen of Providencia alcalifaciens O40

The O-polysaccharide chain of the lipopolysaccharide (O-antigen) on the bacterial cell surface is one of the most structurally variable cell components and serves as a basis for serotyping of Gram-negative bacteria, including human opportunistic pathogens of the genus Providencia. In this work, the O-antigen of Providencia alcalifaciens O40 was obtained by mild acid degradation of the isolated lipopolysaccharide and studied by chemical methods and high-resolution NMR spectroscopy. The following structure of the O-polysaccharide was established: →4)-β-D-Quip3NFo-(1→3)-α-D-Galp-(1→3)-β-D-GlcpA-(1→3)-β-D-GalpNAc-(1→, where GlcA stands for glucuronic acid and Qui3NFo for 3,6-dideoxy-3-formamidoglucose. The O40-antigen was found to be structurally and serologically related to the O-antigens of P. alcalifaciens O5 and Providencia stuartii O18. The O40-antigen gene cluster between cpxA and yibK was sequenced, and the gene functions were predicted in silico. In agreement with the O-polysaccharide structure established, the genes for the synthesis of dTDP-D-Qui3NFo, UDP-D-Gal, UDP-D-GlcA, and UDP-D-GalNAc as well as those encoding three glycosyltransferases, flippase (Wzx), and O-antigen polymerase (Wzy) were recognized. In addition, homologues of wza, wzb, and wzc genes, which are required for the surface expression of capsular polysaccharides, were found within the gene cluster, suggesting that the O-polysaccharide studied is a part of the capsule-related form of the lipopolysaccharide called K(LPS).

Localization and molecular characterization of putative O antigen gene clusters of Providencia species

Enterobacteria of the genus Providencia are opportunistic human pathogens associated with urinary tract and wound infections, as well as enteric diseases. The lipopolysaccharide (LPS) O antigen confers major antigenic variability upon the cell surface and is used for serotyping of Gram-negative bacteria. Recently, Providencia O antigen structures have been extensively studied, but no data on the location and organization of the O antigen gene cluster have been reported. In this study, the four Providencia genome sequences available were analysed, and the putative O antigen gene cluster was identified in the polymorphic locus between the cpxA and yibK genes. This finding provided the necessary information for designing primers, and cloning and sequencing the O antigen gene clusters from five more Providencia alcalifaciens strains. The gene functions predicted in silico were in agreement with the known O antigen structures; furthermore, annotation of the genes involved in the three-step synthesis of GDP-colitose (gmd, colD and colC) was supported by cloning and biochemical characterization of the corresponding enzymes. In one strain (P. alcalifaciens O39), no polysaccharide product of the gene cluster in the cpxA-yibK locus was found, and hence genes for synthesis of the existing O antigen are located elsewhere in the genome. In addition to the putative O antigen synthesis genes, homologues of wza, wzb, wzc and (in three strains) wzi, required for the surface expression of capsular polysaccharides, were found upstream of yibK in all species except Providencia rustigianii, suggesting that the LPS of these species may be attributed to the so-called K LPS (K(LPS)). The data obtained open a way for development of a PCR-based typing method for identification of Providencia isolates.

Molecular characterization of Cronobacter lipopolysaccharide O-antigen gene clusters and development of serotype-specific PCR assays

Cronobacter (formerly Enterobacter sakazakii) is a recently defined genus consisting of six species, C. sakazakii, C. malonaticus, C. dublinensis, C. muytjensii, C. turicensis, and Cronobacter genomospecies 1. In this study, MboII restriction fragment length polymorphism (RFLP) patterns of O-antigen gene clusters, located between galF and gnd, were used to identify serotypes in Cronobacter spp. Seven O-antigen RFLP clusters were generated, including three C. sakazakii clusters, previously identified as serotypes O1, O2, and O3. The O-antigen regions of six strains with unique RFLP patterns, including two C. sakazakii strains, two C. malonaticus strains, one C. turicensis strain, and one C. muytjensii strain, revealed three O-antigen gene clusters shared among Cronobacter species. PCR assays were developed, targeting the wzx O-antigen polymerase gene, and used to screen 231 Cronobacter strains to determine the frequency of these newly identified serotypes.

Characterization of the O-antigen in the lipopolysaccharide of Cronobacter (Enterobacter) malonaticus 3267

Cronobacter malonaticus, a Gram-negative bacterium previously known as Enterobacter sakazakii, is an opportunistic pathogen known to cause serious infection in infants and neonates. To provide aid for the serological and chemical identification of clinical, environmental, or food isolates of this emerging pathogen, the characterization of the lipopolysaccharide (LPS) O-polysaccharide (O-PS) antigens of Cronobacter spp. is being undertaken. The structural analysis of the O-PS, obtained by hydrazinolysis of the lipopolysaccharide produced by Cronobacter malonaticus HPB 3267, was investigated by composition, methylation, and two-dimensional high-resolution nuclear magnetic resonance methods, and was found to be a polymer of a branched pentasaccharide unit. This unit is composed of D-glucose (D-Glc), D-galactose (D-Gal), 2-amino-2-deoxy-D-glucose (D-GlcN), 2-amino-2-deoxy-D-galactose (D-GalN) and 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) residues (1: 1: 1: 1: 1), forms the repeating oligosaccharide in the O-PS antigen, and has the structure: [structure: see text].

New structure for the O-polysaccharide of Providencia alcalifaciens O27 and revised structure for the O-polysaccharide of Providencia stuartii O43

The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide from Providencia alcalifaciens O27 and studied by sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy, including 2D (1)H,(1)H COSY, TOCSY, ROESY, H-detected (1)H,(13)C HSQC, and HMBC experiments. It was found that the polysaccharide is built up of linear partially O-acetylated tetrasaccharide repeating units and has the following structure: [structure: see text] where Qui4NFo stands for 4-formamido-4,6-dideoxyglucose (4-formamido-4-deoxyquinovose). The O-polysaccharide structure of Providencia stuartii O43 established earlier was revised with respect to the configuration of the constituent 4-amino-4,6-dideoxyhexose (from Rha4N to Qui4N).