Lipopolysaccharides of bacterial pathogens from the genus Yersinia: a mini-review

The Threat of Potentially Pathogenic Bacteria in the Feces of Bats

Bats have attracted global attention because of their zoonotic association with severe acute respiratory syndrome coronavirus (SARS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Previous and ongoing studies have predominantly focused on bat-borne viruses; however, the prevalence or abundance of bat-borne pathogenic bacteria and their potential public health significance have largely been neglected. For the first time, this study used both metataxonomics (16S rRNA marker gene sequencing) and culturomics (traditional culture methods) to systematically evaluate the potential public health significance of bat fecal pathogenic bacteria. To this end, fecal samples were obtained from five bat species across different locations in China, and their microbiota composition was analyzed. The results revealed that the bat microbiome was most commonly dominated by Proteobacteria, while the strictly anaerobic phylum Bacteroidetes occupied 35.3% of the relative abundance in Rousettus spp. and 36.3% in Hipposideros spp., but less than 2.7% in the other three bat species (Taphozous spp., Rhinolophus spp., and Myotis spp.). We detected 480 species-level phylotypes (SLPs) with PacBio sequencing, including 89 known species, 330 potentially new species, and 61 potentially higher taxa. In addition, a total of 325 species were identified by culturomics, and these were classified into 242 named species and 83 potentially novel species. Of note, 32 of the 89 (36.0%) known species revealed by PacBio sequencing were found to be pathogenic bacteria, and 69 of the 242 (28.5%) known species isolated by culturomics were harmful to people, animals, or plants. Additionally, nearly 40 potential novel species which may be potential bacterial pathogens were identified. IMPORTANCE Bats are one of the most diverse and widely distributed groups of mammals living in close proximity to humans. In recent years, bat-borne viruses and the viral zoonotic diseases associated with bats have been studied in great detail. However, the prevalence and abundance of pathogenic bacteria in bats have been largely ignored. This study used high-throughput sequencing techniques (metataxonomics) in combination with traditional culture methods (culturomics) to analyze the bacterial flora in bat feces from different species of bats in China, revealing that bats are natural hosts of pathogenic bacteria and carry many unknown bacteria. The results of this study can be used as guidance for future investigations of bacterial pathogens in bats.

Yersinia Outer Membrane Vesicles as Potential Vaccine Candidates in Protecting against Plague

Despite the relatively low incidence of plague, its etiological agent, Yersinia pestis, is an exceptional epidemic danger due to the high infectivity and mortality of this infectious disease. Reports on the isolation of drug-resistant Y. pestis strains indicate the advisability of using asymmetric responses, such as phage therapy and vaccine prophylaxis in the fight against this problem. The current relatively effective live plague vaccine is not approved for use in most countries because of its ability to cause heavy local and system reactions and even a generalized infectious process in people with a repressed immune status or metabolic disorders, as well as lethal infection in some species of nonhuman primates. Therefore, developing alternative vaccines is of high priority and importance. However, until now, work on the development of plague vaccines has mainly focused on screening for the potential immunogens. Several investigators have identified the protective potency of bacterial outer membrane vesicles (OMVs) as a promising basis for bacterial vaccine candidates. This review is aimed at presenting these candidates of plague vaccine and the results of their analysis in animal models.

Yersinia Phages and Food Safety

One of the human- and animal-pathogenic species in genus Yersinia is Yersinia enterocolitica, a food-borne zoonotic pathogen that causes enteric infections, mesenteric lymphadenitis, and sometimes sequelae such as reactive arthritis and erythema nodosum. Y. enterocolitica is able to proliferate at 4 C, making it dangerous if contaminated food products are stored under refrigeration. The most common source of Y. enterocolitica is raw pork meat. Microbiological detection of the bacteria from food products is hampered by its slow growth rate as other bacteria overgrow it. Bacteriophages can be exploited in several ways to increase food safety with regards to contamination by Y. enterocolitica. For example, Yersinia phages could be useful in keeping the contamination of food products under control, or, alternatively, the specificity of the phages could be exploited in developing rapid and sensitive diagnostic tools for the identification of the bacteria in food products. In this review, we will discuss the present state of the research on these topics.

Genetics and evolution of Yersinia pseudotuberculosis O-specific polysaccharides: a novel pattern of O-antigen diversity

O-antigen polysaccharide is a major immunogenic feature of the lipopolysaccharide of Gram-negative bacteria, and most species produce a large variety of forms that differ substantially from one another. There are 18 known O-antigen forms in the Yersinia pseudotuberculosis complex, which are typical in being composed of multiple copies of a short oligosaccharide called an O unit. The O-antigen gene clusters are located between the hemH and gsk genes, and are atypical as 15 of them are closely related, each having one of five downstream gene modules for alternative main-chain synthesis, and one of seven upstream modules for alternative side-branch sugar synthesis. As a result, many of the genes are in more than one gene cluster. The gene order in each module is such that, in general, the earlier a gene product functions in O-unit synthesis, the closer the gene is to the 5΄ end for side-branch modules or the 3΄ end for main-chain modules. We propose a model whereby natural selection could generate the observed pattern in gene order, a pattern that has also been observed in other species.

Review: Lipopolysaccharide inner core oligosaccharide structure and outer membrane stability in human pathogens belonging to the Enterobacteriaceae

In the Enterobacteriaceae, the outer membrane is primarily comprised of lipopolysaccharides. The lipopolysaccharide molecule is important in mediating interactions between the bacterium and its environment and those regions of the molecule extending further away from the cell surface show a higher amount of structural diversity. The hydrophobic lipid A is highly conserved, due to its important role in the structural integrity of the outer membrane. Attached to the lipid A region is the core oligosaccharide. The inner core oligosaccharide (lipid A proximal) backbone is also well conserved. However, non-stoichiometric substitutions of the basic inner core structure lead to structural variation and microheterogeneity. These include the addition of negatively charged groups (phosphate or galacturonic acid), ethanolamine derivatives, and glycose residues (Kdo, rhamnose, galactose, glucosamine, N-acetylglucosamine, heptose, Ko). The genetics and biosynthesis of these substitutions is beginning to be elucidated. Modification of heptose residues with negatively charged molecules (such as phosphate in Escherichia coli and Salmonella and galacturonic acid in Klebsiella pneumoniae ) has been shown to be involved in maintaining membrane stability. However, the biological role(s) of the remaining substitutions is unknown.

Yersinia enterocolitica-Specific Infection by Bacteriophages TG1 and ϕR1-RT Is Dependent on Temperature-Regulated Expression of the Phage Host Receptor OmpF

Bacteriophages present huge potential both as a resource for developing novel tools for bacterial diagnostics and for use in phage therapy. This potential is also valid for bacteriophages specific for Yersinia enterocolitica To increase our knowledge of Y. enterocolitica-specific phages, we characterized two novel yersiniophages. The genomes of the bacteriophages vB_YenM_TG1 (TG1) and vB_YenM_ϕR1-RT (ϕR1-RT), isolated from pig manure in Canada and from sewage in Finland, consist of linear double-stranded DNA of 162,101 and 168,809 bp, respectively. Their genomes comprise 262 putative coding sequences and 4 tRNA genes and share 91% overall nucleotide identity. Based on phylogenetic analyses of their whole-genome sequences and large terminase subunit protein sequences, a genus named Tg1virus within the family Myoviridae is proposed, with TG1 and ϕR1-RT (R1RT in the ICTV database) as member species. These bacteriophages exhibit a host range restricted to Y. enterocolitica and display lytic activity against the epidemiologically significant serotypes O:3, O:5,27, and O:9 at and below 25°C. Adsorption analyses of lipopolysaccharide (LPS) and OmpF mutants demonstrate that these phages use both the LPS inner core heptosyl residues and the outer membrane protein OmpF as phage receptors. Based on RNA sequencing and quantitative proteomics, we also demonstrate that temperature-dependent infection is due to strong repression of OmpF at 37°C. In addition, ϕR1-RT was shown to be able to enter into a pseudolysogenic state. Together, this work provides further insight into phage-host cell interactions by highlighting the importance of understanding underlying factors which may affect the abundance of phage host receptors on the cell surface.

IMPORTANCE

Only a small number of bacteriophages infecting Y. enterocolitica, the predominant causative agent of yersiniosis, have been previously described. Here, two newly isolated Y. enterocolitica phages were studied in detail, with the aim of elucidating the host cell receptors required for infection. Our research further expands the repertoire of phages available for consideration as potential antimicrobial agents or as diagnostic tools for this important bacterial pathogen.

Interaction of human mannose-binding lectin (MBL) with Yersinia enterocolitica lipopolysaccharide

The lipopolysaccharide (LPS) is involved in the interaction between Gram-negative pathogenic bacteria and host. Mannose-binding lectin (MBL), complement-activating soluble pattern-recognition receptor targets microbial glycoconjugates, including LPS. We studied its interactions with a set of Yersinia enterocolitica O:3 LPS mutants. The wild-type strain LPS consists of lipid A (LA) substituted with an inner core oligosaccharide (IC) which in turn is substituted either with the O-specific polysaccharide (OPS) or the outer core hexasaccharide (OC), and sometimes also with the enterobacterial common antigen (ECA). The LPS mutants produced truncated LPS, missing OPS, OC or both, or, in addition, different IC constituents or ECA. MBL bound to LA-IC, LA-IC-OPS and LA-IC-ECA but not LA-IC-OC structures. Moreover, LA-IC substitution with both OPS and ECA prevented the lectin binding. Sequential truncation of the IC heptoses demonstrated that the MBL targets the IC heptose region. Furthermore, microbial growth temperature influenced MBL binding; binding was stronger to bacteria grown at room temperature (22°C) than to bacteria grown at 37°C. In conclusion, our results demonstrate that MBL can interact with Y. enterocolitica LPS, however, the in vivo significance of that interaction remains to be elucidated.

Two host clades, two bacterial arsenals: evolution through gene losses in facultative endosymbionts

Bacterial endosymbiosis is an important evolutionary process in insects, which can harbor both obligate and facultative symbionts. The evolution of these symbionts is driven by evolutionary convergence, and they exhibit among the tiniest genomes in prokaryotes. The large host spectrum of facultative symbionts and the high diversity of strategies they use to infect new hosts probably impact the evolution of their genome and explain why they undergo less severe genomic erosion than obligate symbionts. Candidatus Hamiltonella defensa is suitable for the investigation of the genomic evolution of facultative symbionts because the bacteria are engaged in specific relationships in two clades of insects. In aphids, H. defensa is found in several species with an intermediate prevalence and confers protection against parasitoids. In whiteflies, H. defensa is almost fixed in some species of Bemisia tabaci, which suggests an important role of and a transition toward obligate symbiosis. In this study, comparisons of the genome of H. defensa present in two B. tabaci species (Middle East Asia Minor 1 and Mediterranean) and in the aphid Acyrthosiphon pisum revealed that they belong to two distinct clades and underwent specific gene losses. In aphids, it contains highly virulent factors that could allow protection and horizontal transfers. In whiteflies, the genome lost these factors and seems to have a limited ability to acquire genes. However it contains genes that could be involved in the production of essential nutrients, which is consistent with a primordial role for this symbiont. In conclusion, although both lineages of H. defensa have mutualistic interactions with their hosts, their genomes follow distinct evolutionary trajectories that reflect their phenotype and could have important consequences on their evolvability.

Structure and genetic basis of Yersinia similis serotype O:9 O-specific polysaccharide

The O-polysaccharide (OPS, O-Ag) cap of LPS is a major virulence factor of Yersinia species and also serves as a receptor for the binding of lytic bacteriophage φR1-37. Currently, the OPS-based serotyping scheme for the Yersinia pseudotuberculosis complex includes 21 known O-serotypes that follow three distinct lineages: Y. pseudotuberculosis sensu stricto, Y. similis and the Korean group of strains. Elucidation of the Y. pseudotuberculosis complex OPS structures and characterization of the OPS genetics (altogether 18 O-serotypes studied thus far) allows a better understanding of the relationships among the various O serotypes and will facilitate the analysis of the evolutionary processes giving rise to new serotypes. Here we present the characterization of the OPS structure and gene cluster of Y. similis O:9. Bacteriophage φR1-37, which uses the Y. similis O:9 OPS as a receptor, also infects a number of Y. enterocolitica serotypes, including O:3, O:5,27, O:9 and O:50. The Y. similis O:9 OPS structure resembled none of the receptor structures of the Y. enterocolitica strains, suggesting that φR1-37 can recognize several surface receptors, thus promoting broad host specificity.

A novel post-exposure medical countermeasure L-97-1 improves survival and acute lung injury following intratracheal infection with Yersinia pestis

Yersinia pestis, a Gram-negative bacillus causing plague and Centers for Disease Control and Prevention (CDC) classified Category A pathogen, has high potential as a bioweapon. Lipopolysaccharide, a virulence factor for Y. pestis, binds to and activates A(1) adenosine receptor (AR)s and, in animals, A(1)AR antagonists block induced acute lung injury (ALI) and increase survival following cecal ligation and perforation. In this study, rats were infected intratracheally with viable Y. pestis [CO99 (pCD1( + )/Δpgm) 1 × 10( 8 ) CFU/animal] and treated daily for 3 d with ciprofloxacin (cipro), the A(1)AR antagonist L-97-1, or cipro plus L-97-1 starting at 0, 6, 24, 48, or 72 h post-Y. pestis. At 72 h post-Y. pestis, cipro plus L-97-1 significantly improved 6-d survival to 60-70% vs 28% for cipro plus H(2)O and 33% for untreated Y. pestis controls (P = 0.02, logrank test). Lung edema, hemorrhage and leukocyte infiltration index (LII) were evaluated histologically to produce ALI scores. Cipro plus L-97-1 significantly reduced lung edema, as well as aggregate lung injury scores vs controls or cipro plus H(2)O, and LII vs controls (P < 0.05, Student's unpaired t test). These results support efficacy for L-97-1 as a post-exposure medical countermeasure, adjunctive therapy to antibiotics for Y. pestis.

Bacterial cell surface structures in Yersinia enterocolitica

Yersinia enterocolitica is a widespread member of the family of Enterobacteriaceae that contains both non-virulent and virulent isolates. Pathogenic Y. enterocolitica strains, especially belonging to serotypes O:3, O:5,27, O:8 and O:9 are etiologic agents of yersiniosis in animals and humans. Y. enterocolitica cell surface structures that play a significant role in virulence have been subject to many investigations. These include outer membrane (OM) glycolipids such as lipopolysaccharide (LPS) and enterobacterial common antigen (ECA) and several cell surface adhesion proteins present only in virulent Y. enterocolitica, i.e., Inv, YadA and Ail. While the yadA gene is located on the Yersinia virulence plasmid the Ail, Inv, LPS and ECA are chromosomally encoded. These structures ensure the correct architecture of the OM, provide adhesive properties as well as resistance to antimicrobial peptides and to host innate immune response mechanisms.

Identification of distinct lipopolysaccharide patterns among Yersinia enterocolitica and Y. enterocolitica-like bacteria

The lipopolysaccharide (LPS) of strains representing various serotypes of Yersinia enterocolitica and Y. enterocolitica-like bacteria was studied by deoxycholate-PAGE and silver staining analysis. Four main types of LPS were detected based on the O-polysaccharide (O-PS): (i) LPS with homopolymeric O-PS, (ii) LPS with ladder-forming heteropolymeric O-PS, (iii) LPS with single-length O-PS, and (iv) semi-rough LPS without O-PS. Within the first three types, several subvariants were detected. Selected serotypes representing all above LPS types are sensitive to bacteriophage φR1-37 indicating that they share the phage receptor, a hexasaccharide called outer core in Y. enterocolitica O:3. Whereas phage φR1-37-resistant mutants of homopolymeric O-PS have lost only the outer core, those of ladder-forming or single-length O-PS have lost also the O-PS suggesting that in the latter ones the outer core is bridging between O-PS and lipid A-core. This work forms a basis of further structural, biochemical and genetic studies of these LPSs.

Functional characterization and biological significance of Yersinia pestis lipopolysaccharide biosynthesis genes

In silico analysis of available bacterial genomes revealed the phylogenetic proximity levels of enzymes responsible for biosynthesis of lipopolysaccharide (LPS) of Yersinia pestis, the cause of plague, to homologous proteins of closely related Yersinia spp. and some other bacteria (Serratia proteamaculans, Erwinia carotovora, Burkholderia dolosa, Photorhabdus luminescens and others). Isogenic Y. pestis mutants with single or double mutations in 14 genes of LPS biosynthetic pathways were constructed by site-directed mutagenesis on the base of the virulent strain 231 and its attenuated derivative. Using high-resolution electrospray ionization mass spectrometry, the full LPS structures were elucidated in each mutant, and the sequence of monosaccharide transfers in the assembly of the LPS core was inferred. Truncation of the core decreased significantly the resistance of bacteria to normal human serum and polymyxin B, the latter probably as a result of a less efficient incorporation of 4-amino-4-deoxyarabinose into lipid A. Impairing of LPS biosynthesis resulted also in reduction of LPS-dependent enzymatic activities of plasminogen activator and elevation of LD(50) and average survival time in mice and guinea pigs infected with experimental plague. Unraveling correlations between biological properties of bacteria and particular LPS structures may help a better understanding of pathogenesis of plague and implication of appropriate genes as potential molecular targets for treatment of plague.

Interaction of concanavalin a with bacterial lipopolysaccharides in agarose gel

Binding of fluorescein isothiocyanate-labeled concanavalin A to a series of molecular species of lipopolysaccharide (LPS), purified from pathogenic bacteria, was studied via agarose gel precipitation experiments and the results were compared with available structural data.The LPS species could be divided into ConA-reactive and non-reactive ones. Reactivity resided in the O-specific chain of LPS, and binding to the lipid A or core moieties of LPS could not be demonstrated by the present methods. The α-D-glucose or α-D-mannose residues of the repeating O-specific oligosaccharide units appeared to be recognized by ConA, except when blocked by steric hindrance. Specificity of the reaction was verified by inhibition with 2% D-glucose. Binding by bacterium-specific sugar-residues could not be demonstrated.For precipitation to occur, polyvalency was required both for LPS and ConA, and the resulting precipitation appeared to be promoted by hydrophobic interactions between the lipid A moieties of LPS molecules. The LPS species were differently retained by the agarose gel, which can be explained by differences in their micellar structure in aqueous solution. E. coli O83 LPS did not readily diffused in 1% agarose gel, but its precipitation with ConA could be demonstrated either at elevated temperature or mixing it previously with molten agarose (Mancini's arrangement).

Identification of the lipopolysaccharide core of Yersinia pestis and Yersinia pseudotuberculosis as the receptor for bacteriophage φA1122

φA1122 is a T7-related bacteriophage infecting most isolates of Yersinia pestis, the etiologic agent of plague, and used by the CDC in the identification of Y. pestis. φA1122 infects Y. pestis grown both at 20 °C and at 37 °C. Wild-type Yersinia pseudotuberculosis strains are also infected but only when grown at 37 °C. Since Y. pestis expresses rough lipopolysaccharide (LPS) missing the O-polysaccharide (O-PS) and expression of Y. pseudotuberculosis O-PS is largely suppressed at temperatures above 30 °C, it has been assumed that the phage receptor is rough LPS. We present here several lines of evidence to support this. First, a rough derivative of Y. pseudotuberculosis was also φA1122 sensitive when grown at 22 °C. Second, periodate treatment of bacteria, but not proteinase K treatment, inhibited the phage binding. Third, spontaneous φA1122 receptor mutants of Y. pestis and rough Y. pseudotuberculosis could not be isolated, indicating that the receptor was essential for bacterial growth under the applied experimental conditions. Fourth, heterologous expression of the Yersinia enterocolitica O:3 LPS outer core hexasaccharide in both Y. pestis and rough Y. pseudotuberculosis effectively blocked the phage adsorption. Fifth, a gradual truncation of the core oligosaccharide into the Hep/Glc (L-glycero-D-manno-heptose/D-glucopyranose)-Kdo/Ko (3-deoxy-D-manno-oct-2-ulopyranosonic acid/D-glycero-D-talo-oct-2-ulopyranosonic acid) region in a series of LPS mutants was accompanied by a decrease in phage adsorption, and finally, a waaA mutant expressing only lipid A, i.e., also missing the Kdo/Ko region, was fully φA1122 resistant. Our data thus conclusively demonstrated that the φA1122 receptor is the Hep/Glc-Kdo/Ko region of the LPS core, a common structure in Y. pestis and Y. pseudotuberculosis.

Divergence of biochemical function in the HAD superfamily: D-glycero-D-manno-heptose-1,7-bisphosphate phosphatase (GmhB)

D-Glycero-d-manno-heptose-1,7-bisphosphate phosphatase (GmhB) is a member of the histidinol-phosphate phosphatase (HisB) subfamily of the haloalkanoic acid dehalogenase (HAD) enzyme superfamily. GmhB supports two divergent biochemical pathways in bacteria: the d-glycero-d-manno-heptose-1alpha-GDP pathway (in S-layer glycoprotein biosynthesis) and the l-glycero-d-manno-heptose-1beta-ADP pathway (in lipid A biosynthesis). Herein, we report the comparative analysis of substrate recognition in selected GmhB orthologs. The substrate specificity of the l-glycero-d-manno-heptose-1beta-ADP pathway GmhB from Escherichia coli K-12 was evaluated using hexose and heptose bisphosphates, histidinol phosphate, and common organophosphate metabolites. Only d-glycero-d-manno-heptose 1beta,7-bisphosphate (k(cat)/K(m) = 7 x 10(6) M(-1) s(-1)) and d-glycero-d-manno-heptose 1alpha,7-bisphosphate (k(cat)/K(m) = 7 x 10(4) M(-1) s(-1)) displayed physiologically significant substrate activity. (31)P NMR analysis demonstrated that E. coli GmhB selectively removes the C(7) phosphate. Steady-state kinetic inhibition studies showed that d-glycero-d-manno-heptose 1beta-phosphate (K(is) = 60 microM, and K(ii) = 150 microM) and histidinol phosphate (K(is) = 1 mM, and K(ii) = 6 mM), while not hydrolyzed, do in fact bind to E. coli GmhB, which leads to the conclusion that nonproductive binding contributes to substrate discrimination. High catalytic efficiency and a narrow substrate range are characteristic of a well-evolved metabolic enzyme, and as such, E. coli GmhB is set apart from most HAD phosphatases (which are typically inefficient and promiscuous). The specialization of the biochemical function of GmhB was examined by measuring the kinetic constants for hydrolysis of the alpha- and beta-anomers of d-glycero-d-manno-heptose 1beta,7-bisphosphate catalyzed by the GmhB orthologs of the l-glycero-d-manno-heptose 1beta-ADP pathways operative in Bordetella bronchiseptica and Mesorhizobium loti and by the GmhB of the d-glycero-d-manno-heptose 1alpha-GDP pathway operative in Bacteroides thetaiotaomicron. The results show that although each of these representatives possesses physiologically significant catalytic activity toward both anomers, each displays substantial anomeric specificity. Like E. coli GmhB, B. bronchiseptica GmhB and M. loti GmhB prefer the beta-anomer, whereas B. thetaiotaomicron GmhB is selective for the alpha-anomer. By determining the anomeric configuration of the physiological substrate (d-glycero-d-manno-heptose 1,7-bisphosphate) for each of the four GmhB orthologs, we discovered that the anomeric specificity of GmhB correlates with that of the pathway kinase. The conclusion drawn from this finding is that the evolution of the ancestor to GmhB in the HisB subfamily provided for specialization toward two distinct biochemical functions.

Prospects for new plague vaccines

The potential application of Yersinia pestis for bioterrorism emphasizes the urgent need to develop more effective vaccines against airborne infection. The current status of plague vaccines has been reviewed. The present emphasis is on subunit vaccines based on the F1 and LcrV antigens. These provide good protection in animal models but may not protect against F1 strains with modifications to the type III secretion system. The duration of protection against pneumonic infection is also uncertain. Other strategies under investigation include defined live-attenuated vaccines, DNA vaccines, mucosal delivery systems and heterologous immunization. The live-attenuated strain Y. pestis EV NIIEG protects against aerosol challenge in animal models and, with further modification to reduce residual virulence and to optimize respiratory protection, it could provide a shortcut to improved vaccines. The regulatory problems inherent in licensing vaccines for which efficacy data are unavailable and their possible solutions are discussed herein.

Fatal yersiniosis in farmed deer caused by Yersinia pseudotuberculosis serotype O:3 encoding a mannosyltransferase-like protein WbyK

Sudden death of 9 deer occurred in a large enclosed deer farm with approximately 400 heads of cervids. Fatal yersiniosis was diagnosed in 2 deer that were submitted for laboratory diagnosis. Histopathologically, the disease was characterized by multifocal pulmonary hemorrhage and mild interstitial pneumonia, marked diffuse cholangiohepatitis, minimal myocarditis with mild myocardial degeneration, and mild multifocal suppurative cystic colitis. Yersinia pseudotuberculosis was isolated from the lungs and colon of the affected animals. The isolates were PCR-positive for genes virF, inv, yopB, and yopH, which are essential for invasion and colonization of host intestine and lung. The isolates reacted with polyclonal antibodies against serotype O:3 antigen. The O-genotyping patterns of the isolates were identical with each other, but different from those of the 21 O-genotypes (or serotypes) reported previously. In addition to the O-antigen genes possessed by classical serotype O:3, a gene (wbyK) encoding a mannosyltransferase-like protein was detected in these isolates. The wbyK gene of the isolates showed 94% of DNA sequence homology with the wbyK gene harbored by Y. pseudotuberculosis O:1b. On the basis of pathology, bacteriology, and serology, the authors concluded that the acute deaths of these deer were caused by Y. pseudotuberculosis infection. Molecular characterization of the isolate revealed a genetic heterogeneity in the O-antigen gene cluster of Y. pseudotuberculosis serotype O:3.

Induction of innate immunity by lipid A mimetics increases survival from pneumonic plague

This study analysed the effect of priming the innate immune system using synthetic lipid A mimetics in a Yersinia pestis murine pulmonary infection model. Two aminoalkyl glucosaminide 4-phosphate (AGP) Toll-like receptor 4 (TLR4) ligands, delivered intranasally, extended time to death or protected against a lethal Y. pestis CO92 challenge. The level of protection was dependent upon the challenge dose of Y. pestis and the timing of AGP therapy. Protection correlated with cytokine induction and a decreased bacterial burden in lung tissue. AGP protection was TLR4-dependent and was not evidenced in transgenic TLR4-deficient mice. AGP therapy augmented with subtherapeutic doses of gentamicin produced dramatically enhanced survival. Combined, these results indicated that AGPs may be useful in protection of immunologically naive individuals against plague and potentially other infectious agents, and that AGP therapy may be used synergistically with other therapies.

Genomic comparison of Yersinia pestis and Yersinia pseudotuberculosis by combination of suppression subtractive hybridization and DNA microarray

In order to further figure out the genetic differences between Yersinia pestis and Yersinia pseudotuberculosis, and to provide novel insights into the evolution of Y. pestis, we compared the genomes of Y. pseudotuberculosis serogroup I strain ATCC29833 and Y. pestis Antiqua strain 49006 using a combination of suppression subtractive hybridization (SSH) and comparative genomic hybridization with DNAs from a diverse panel of Y. pestis and Y. pseudotuberculosis strains. SSH followed by BLAST analysis revealed 112 SSH fragments specific to strain ATCC29833, compared to the genomic sequence data of Y. pestis strains CO92, KIM and 91001. We identified 17 SSH fragments that appeared to be newly determined genetic contents of Y. pseudotuberculosis. The combination of SSH and microarray analysis showed that the parallel loss of genes contributed greatly not only to the significant genomic divergence between Y. pestis and Y. pseudotuberculosis but also to the intra-species microevolution of both of species. The results confirmed our earlier hypothesis that Y. pestis Antiqua isolates from the natural plague focus B in China represented the most ancestral strains in China, hence phylogenetically the closest isolates to Y. pseudotuberculosis.

Synthesis of the heteropolysaccharide O antigen of Escherichia coli O52 requires an ABC transporter: structural and genetic evidence

The structural and genetic organization of the Escherichia coli O52 O antigen was studied. As identified by sugar and methylation analysis and nuclear magnetic resonance spectroscopy, the O antigen of E. coli O52 has a partially O-acetylated disaccharide repeating unit (O unit) containing D-fucofuranose and 6-deoxy-D-manno-heptopyranose, as well as a minor 6-deoxy-3-O-methylhexose (most likely, 3-O-methylfucose). The O-antigen gene cluster of E. coli O52, which is located between the galF and gnd genes, was found to contain putative genes for the synthesis of the O-antigen constituents, sugar transferase genes, and ABC-2 transporter genes. Further analysis confirmed that O52 employs an ATP-binding cassette (ABC) transporter-dependent pathway for translocation and polymerization of the O unit. This is the first report of an ABC transporter being involved in translocation of a heteropolysaccharide O antigen in E. coli. Genes specific for E. coli O52 were also identified.