Biosynthesis of the Pseudomonas aeruginosa common polysaccharide antigen by D-Rhamnosyltransferases WbpX and WbpY

Glycoconjugate Journal - The Gram-negative bacterium Pseudomonas aeruginosa simultaneously expresses two O-antigenic glycoforms. While the O-specific antigen (OSA) is variable in composition, the...     

Antigenic bacterial polysaccharides. 30. The structure of the polysaccharide chain of lipopolysaccharide of Pseudomonas syringae pv. syringae 281 (serogroup I)

Anomeric methyl 3-O-(D-mannopyranosyl- and L-rhamnopyranosyl)-beta-D-talopyranosides were synthesised by the stereoselective 1,2-cis- and 1,2-trans manno- and rhamnosylation of methyl 2,4,6-tri-O-acetyl-beta-D-talopyranoside, which has been prepared from methyl beta-D-galactopyranoside by a synthetic scheme including conversion of the C2 configuration. From 13C-NMR spectra of the disaccharides obtained the spectral alpha- and beta-effects of O3-glycosylation of talopyranose were determined.     

Phylogenetic and biological species diversity within the Neurospora tetrasperma complex

The objective of this study was to explore the evolutionary history of the morphologically recognized filamentous ascomycete Neurospora tetrasperma, and to reveal the genetic and reproductive relationships among its individuals and populations. We applied both phylogenetic and biological species recognition to a collection of strains representing the geographic and genetic diversity of N. tetrasperma. First, we were able to confirm a monophyletic origin of N. tetrasperma. Furthermore, we found nine phylogenetic species within the morphospecies. When using the traditional broad biological species recognition all investigated strains of N. tetrasperma constituted a single biological species. In contrast, when using a quantitative measurement of the reproductive success, incorporating characters such as viability and fertility of offspring, we found a high congruence between the phylogenetic and biological species recognition. Taken together, phylogenetically and biologically defined groups of individuals exist in N. tetrasperma, and these should be taken into account in future studies of its life history traits.     

Immunological studies of an artificial antigen with specificity of a common polysaccharide antigen of Pseudomonas aeruginosa

Abstract Synthetic d -rhamnan, with the structure of Pseudomonas aeruginosa common polysaccharide antigen (CPA), was conjugated with BSA. The artificial antigen obtained, and the natural antigens, lipopolysaccharides (LPS) of P. aeruginosa and Pseudomonas cerasi with rhamnan chains of the same structure, were studied by ELISA with rabbit antibodies to the d -rhamnan-BSA conjugate and to the P. cerasi O-antigen. Immunological relations between the LPS of P. aeruginosa and P. cerasi determined by CPA as well as between these LPS and d -rhamnan-BSA were revealed by ELISA. O-antiserum to P. cerasi possesses protective activity in the mouse passive protection test when mice are challenged with some P. aeruginosa strains; the antiserum to the d -rhamnan-BSA does not possess protective activity in mice.     

Allelic diversity at the primate major histocompatibility complex DRB6 locus

The HLA-DRB6 gene (also called DRB/V1) has been found only in about 26% of human HLA haplotypes, i.e.; DR1, DRw10, and DR2-bearing ones (Corell et al. 1991). In contrast, exon-2 DRB6 sequences have been obtained from all tested primates: nine chimpanzees (Pan troglodytes), three gorillas (Gorilla gorilla) and three orangutans (Pongo pygmaeus); other apes which had already been sequenced (one gorilla and one chimpanzee) also had the DRB6 gene. Thus, all apes tested from three different species, some of them evolutionary separated by at least 14–16 million years, bear the DRB6 gene. In addition, more than one gene copy per haplotype has been found in one chimpanzee; this, together with the apparent loss of this gene in some of the human DR haplotypes, may indicate that the DR genome has undergone evolutionary changes more recently and more actively than class I or III genes. In addition, ten different and presumably allelic DRB6 exon-2 sequences have been obtained, and some of them coming from different species are more similar to each other than the one from the same species; this finding goes in favor of the trans-species theory of major histocompatibility complex polymorphism generation. Also, data are presented supporting that DRB6 may be one of the eldest genes of the DRB family, thus one of the first to diverge from the ancestral DRB gene.The contribution to this paper by A. Corell and P. Morales is equal, and the order of the authorship is arbitrary.     

Variation within Pseudomonas syringae pv. philadelphi, the cause of a leaf spot of Philadelphus spp.

R oberts , S.J. 1985. Variation within Pseudomonas syringae pv. philadelphi , the cause of a leaf spot of Philadelphius spp. Journal of Applied Bacteriology 59 , 283–290
In pathogenicity tests on Philadelphus and other plant species, belonging to ten genera in seven families, isolates of Pseudomonas syringae from leaf spots on Philadelphus spp. in England did not produce symptoms on any plants other than Philadelphus . It is therefore proposed that these isolates should be designated a distinct pathovar of Ps. syringae with the name Pseudomonas syringae pv. philadelphi . Isolates of this new pathovar varied in their reactions to 6 of 57 biochemical tests. In phage typing tests isolates also varied in their sensitivity to five of seven bacteriophage strains. Four of the six biochemical tests (aesculin hydrolysis, utilization of DL-homoserine L-leucine and sorbitol) and all five of the phages (P11, Pls, P2, A15, and A26) were used to separate the isolates into seven groups. These groups had some relation to their geographical origin, species of Philadelphus from which they were originally isolated, and relative virulence on P. coronarius and P. x purpureo-maculatus . They may represent ecotypes of this new pathovar.     

Studies of the polysaccharide fraction from the lipopolysaccharide of Pseudomonas alcaligenes

Studies of the lipopolysaccharide of Pseudomonas alcaligenes strain BR 1/2 were extended to the polysaccharide moiety. The crude polysaccharide, obtained by mild acid hydrolysis of the lipopolysaccharide, was fractionated by gel filtration. The major fraction was the phosphorylated polysaccharide, for which the approximate proportions of residues were; glucose (2), rhamnose (0.7), heptose (2-3), galactosamine (1), alanine (1), 3-deoxy-2-octulonic acid (1), phosphorus (5-6). The heptose was l-glycero-d-manno-heptose. The minor fractions from gel filtration contained free 3-deoxy-2-octulonic acid, P(i) and PP(i). The purified polysaccharide was studied by periodate oxidation, methylation analysis, partial hydrolysis, and dephosphorylation. All the rhamnose and part of the glucose and heptose occur as non-reducing terminal residues. Other glucose residues are 3-substituted, and most heptose residues are esterified with condensed phosphate residues, possibly in the C-4 position. Free heptose and a heptosylglucose were isolated from a partial hydrolysate of the polysaccharide. The location of galactosamine in the polysaccharide was not established, but either the C-3 or C-4 position appears to be substituted and a linkage to alanine was indicated. In its composition, the polysaccharide from Ps. alcaligenes resembles core polysaccharides from other pseudomonads: no possible side-chain polysaccharide was detected.     

Diversifying selection drives the evolution of the type III secretion system pilus of Pseudomonas syringae

The plant pathogenic bacterium Pseudomonas syringae uses a type III secretion system to inject virulence proteins directly into the cytoplasm of its hosts. The P. syringae type III secretion apparatus is encoded, in part, by the HrpZ operon, which carries the hrpA gene encoding the pilin subunit of the pilus, various components of the structural apparatus, and the HrpZ harpin protein that is believed to produce pores in the host cell membrane. The pilus of the type III system comes into direct contact with the host cell and is, therefore, a likely target of the host's pathogen surveillance systems. We sequenced and analyzed 22 HrpZ operons from P. syringae strains spanning the diversity of the species. Selection analyses, including K(a)/K(s) tests and Tajima's D, revealed strong diversifying selection acting on the hrpA gene. This form of selection enables pathogens to maintain genetic diversity within their populations and is often driven by selection imposed by host defense systems. The HrpZ operon also revealed a single significant recombination event that dramatically changed the evolutionary relationships among P. syringae strains from 2 quite distinct phylogroups. This recombination event appears to have introduced genetic diversity into a clade of strains that may now be undergoing positive selection. The identification of diversifying selection acting on the Hrp pilus across the whole population sample and positive selection within one P. syringae lineage supports a trench warfare coevolutionary model between P. syringae and its plant hosts.     

Structure of the sidechain of lipopolysaccharide from Pseudomonas syringae pv. morsprunorum C28

The sidechain of the lipopolysaccharide from the phytopathogen Pseudomonas syringae pv. morsprunorum C28 was shown to be composed of D-rhamnose. Using 1H and 13C-NMR spectroscopy, methylation analysis, Smith degradation and optical rotation data, the repeat unit was found to have the structure: ----3)-D-Rhap-(alpha 1----3)-D-Rhap-(alpha 1----2)-D-Rhap-(alpha 1---- and a degree of polymerization of approximately 70. Attention is drawn to the possible prevalence of D-6-deoxyhexoses in the lipopolysaccharides of plant pathogenic bacteria.     

Antigenic polysaccharides of bacteria. 37. Structure of the polysaccharide chain of Pseudomonas syringae pv.tabaci (serogroup VII) lipopolysaccharide]

The structure of the O-specific polysaccharide chain of Pseudomonas syringae pv. tabaci strain 223 (serogroup VII) lipopolysaccharide was established on the basis of one- and two-dimensional 1H NMR analysis, 13C NMR analysis and calculation of optical rotation. The structure determined by the non-destructive way was confirmed by acid hydrolysis and methylation. (Sequence: see text). O-Antigen of the strain studied is similar in structure and serological properties to O-antigens of Pseudomonas syringae strains belonging to serogroup I.     

Genetic diversity within vertebrate species is greater at lower latitudes

The latitudinal gradient of species diversity is one of the oldest recognized patterns in biology. While the cause of the pattern remains debated, the global signal of greater diversity toward the tropics is widely established. Whether the pattern holds for genetic diversity within species, however, has received much less attention. We examine latitudinal variation of intraspecific genetic diversity by contrasting nucleotide distance within low- and high-latitude animal groups. Using mitochondrial DNA markers across 72 vertebrate species that together span six continents, two oceans, and 129 degrees of latitude, we found significantly greater genetic diversity at low latitudes within mammalian species, and trends consistent with this pattern in reptiles, amphibians, fish, and birds. The signal held even after removing species whose current geographic ranges include areas recently covered by glaciers during the late Pleistocene and which presumably have experienced colonization bottlenecks in high latitudes. Higher genetic diversity within species was found at low latitudes also for genera that do not possess higher species richness toward the tropics. Moreover, examination of a subset of species with sufficient sampling across a broad geographic range revealed that genetic variation demonstrates a typical gradient, with mid-latitude populations intermediate in genetic diversity between high and low latitude ones. These results broaden the pattern of the global latitudinal diversity gradient, to now include variation within species. These results are also concordant with other studies indicating that low latitude populations and species are on different evolutionary trajectories than high latitude ones, and we speculate that higher rates of evolution toward the equator are driving the pattern for genetic diversity within species.     

Genetic and plasmid diversity within natural populations of Pseudomonas syringae with various exposures to copper and streptomycin bactericides.

We examined the genetic and plasmid diversity within natural populations of Pseudomonas syringae isolated from three ornamental pear nurseries in eastern Oklahoma. The bactericide spray regimen differed at each nursery; copper and streptomycin, only copper, and no bactericides were applied at nurseries I, II, and III respectively. Resistance to copper (Cur) and resistance to streptomycin (Smr) were determined for 1,938 isolates of P. syringae; isolates from nurseries I and II were generally Cur Sms; whereas most isolates from nursery III were Cus Sms. The plasmid profiles of 362 isolates were determined, and six, one, seven, and four plasmid profiles were obtained for Cur, Smr, Cur Smr, and Cus Sms isolates, respectively. All Smr plasmids contained sequences homologous to the strA and strB Smr genes from broad-host-range plasmid RSF1010 and were associated with Smr transposon Tn5393. Plasmids were placed into two groups on the basis of hybridization to the oriV and par sequences from pOSU900, a cryptic plasmid in P. syringae pv. syringae. A total of 100 randomly chosen P. syringae isolates from nurseries I and III were analyzed for genetic diversity by using the arbitrarily primed PCR (AP-PCR) technique. An analysis of chromosomal genotypes by AP-PCR revealed a high degree of genetic diversity among the isolates, and the results of this analysis indicated that the isolates could be clustered into two distinct groups. The plasmid profiles were specific to isolates belonging to particular AP-PCR groups. Within each AP-PCR group, identical plasmid profiles were produced by isolates that had different chromosomal genotypes, implying that plasmid transfer has played an important role in the dissemination of Cur and Smr within the populations studied.     

Location of the O-methyl groups in the O polysaccharide of Pseudomonas syringae pv. phaseolicola

The O-methylation pattern of the O polysaccharide (OPS) of the lipopolysaccharide of Pseudomonas syringae pv. phaseolicola GSPB 1552 was revealed by methylation (CD3I) analysis, Smith degradation, and NMR spectroscopy. Together with the major O repeats consisting of D-rhamnopyranose (D-Rhap) and D-fucofuranose (D-Fucf), there are minor repeats (approximately 30%) containing 3-O-methyl-D-rhamnose (D-acofriose), which is 2-substituted in the interior repeats and occupies the terminal non-reducing end of the OPS. It was suggested that the methylated O repeats are linked to each other nearby the non-reducing end of the OPS and that the 'biological' O repeat of the OPS has the following structure: [molecular structure: see text].     

Synthesis of the polysaccharide common antigen of Pseudomonas aeruginosa and its L-analog in the form of 6-aminohexyl glycosides

A synthesis of trisaccharide monomers built of D- or L-rhamnose residues is described. Their polycondensation in the presence of a 6-aminohexyl rhamnoside derivative afforded 6-aminohexyl glycosides of the natural common polysaccharide antigen of Pseudomonas aeruginosa and its L-analogue, respectively.