Gluco-oligosaccharide production by a strain of Erwinia amylovora.

When grown in sorbitol-asparagine-salts medium, cells of Erwinia amylovora isolate T83 released a mixture of oligosaccharides and lipopolysaccharide in place of extracellular polysaccharide. The oligosaccharide fraction was usually readily separable from lipopolysaccharide by gel permeation chromatography, but some samples required disaggregation by preliminary treatment with EDTA. By 1H- and 13C-NMR spectroscopy, methylation analysis and mass spectrometry, the oligosaccharide fraction was shown to consist of terminal, beta-1,2- and beta-1,2,6-linked D-glucose residues in the ratio 2.2:2.6:1, indicating a branched oligosaccharide structure. The purified oligosaccharide fraction was partially resolved by gel permeation chromatography into two components containing approximately equal amounts of glucose. When grown on pear slices, isolate T83 produced normal extracellular polysaccharide.

Effect on lipopolysaccharide structure of aeration during growth of a plum isolate of Pseudomonas syringae pv. morsprunorum.

The composition of lipopolysaccharide (LPS) extracted with aqueous phenol from a virulent English plum isolate of Pseudomonas syringae pv. morsprunorum varied according to the partial pressure of oxygen (pO2) in the culture medium at the time of harvest. When pO2 was low, the organism grew slowly and produced smooth LPS bearing rhamnan sidechains. As pO2 was raised, the rate of growth increased and smooth LPS was replaced by a rough species deficient in rhamnose, which co-extracted with a D-glucan. Organization of rhamnose and glucose into separate polymers was shown by the selective susceptibility of the rhamnose-containing polymer to hydrolysis by rhamnanase of the phage A7. By methylation analysis, GC-MS, and 1H- and 13C-NMR spectroscopy, the glucan was shown to consist of alpha (1-->4)-linked residues with alpha (1-->4,6)-branch points and non-reducing terminal residues in the approximate ratio 4:1:1, resembling glycogen in composition. A glucan which co-extracted with LPS using phenol/water from an avirulent plum isolate that was resistant to lysis by phages A1 and A7 was shown by methylation analysis to have a similar structure. Whether the effect on LPS composition was due directly to pO2, or was dependent on the rate of growth, has not been established. It is suggested that, because epiphytic growth would entail exposure to high pO2, English plum isolates growing on the surfaces of host plants might be unable to produce smooth LPS. Since cell surface composition affects virulence in plant-pathogenic pseudomonads, this effect could account for the observed failure of the English plum isolates to enter the host via leaf scars.

Structure of the sidechain of lipopolysaccharide from Erwinia amylovora T.

The sidechain of lipopolysaccharide from Erwinia amylovora T was composed of D-fucose, D-galactose and D-glucose in equimolar proportions. Using NMR spectroscopy, methylation analysis, mass spectrometry, Smith degradation and optical rotation data, the repeat unit was shown to have the following most probable structure: (formula; see text)

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.

Properties of phage-receptor lipopolysaccharide from Pseudomonas morsprunorum.

Lipopolysaccharide (LPS) of Pseudomonas morsprunorum was extracted with hot phenol and purified by repeated centrifuging followed by either block electrophoresis or gel filtration. LPS from a virulent isolate exhibited specific phage inactivation (PI50 = 0.05 mug LPS ml-1), whereas LPS from an avirulent phage-resistant mutant did not. LPS was considered pure when a single band was detected following sodium dodecyl sulphate-cellulose acetate electrophoresis (pH 7.4). It was not phytotoxic when inoculated into cherry leaves at concentrations up to I mg ml-1, but produced weak chlorosis in bean and tobacco at 2 mg ml-1: no visible symptoms appeared after treatment with lower concentrations. The chemical composition of the LPS was partly determined.