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: 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.
Purified LPS from a virulent cherry isolate of Pseudonwnas syringae pv. nwrsprunonun was a mixture of smooth and rough molecular species. Mild acid hydrolysis yielded a precipitate of lipid A and a carbohydrate fraction which, by gel permeation chromatography, yielded three peaks of material. The first (high molecular weight) peak was composed almost entirely of a rhamnan, the sidechain polysaccharide. The second peak contained core oligosaccharide and comprised rhamnose, glucose, heptose, 2-keto-3-deoxyoctonate (KDO), phosphate, glucosamine, galactosamine and alanine. The third (low molecular weight) peak contained KDO, phosphate and ethanolamine. Lipid A contained glucosamine, phosphate and the fatty acids 12:0, 3-OH 10:0, 2-OH 12:O (all ester-linked to glucosamine), and 3-OH 12:0, which was amide-linked. The typing phage A7, which uses LPS as its binding site, was found to possess a rhamnanase which split the sidechains from smooth LPS, releasing them as oligosaccharide.
S U M M A R YLipopolysaccharide (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 exhbited specific phage inactivation (PIso = 0.05 ,ug LPS ml-l), whereas LPS from an avirulent phageresistant 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 mgml-l, but produced weak chlorosis in bean and tobacco at 2 mg ml-l : no visible symptoms appeared after treatment with lower concentrations. The chemical composition of the LPS was partly determined. I N T R O D U C T I O NThere is a strong correlation between phage sensitivity and host specificity in the English isolates of Pseudomonas morsprunorum, the cause of cherry canker (Crosse & Garrett, 1970). Isolates from cherry are sensitive to A7 and related phages (Crosse & Garrett, 1963) and infect cherry trees (Prunus avium) through the leaf scars. Almost all plum strains are insensitive to these phages and are non-virulent through cherry leaf scars. Plum strains adsorb phage A7 as readily as do cherry strains, suggesting that phage-receptor material in the bacterial wall is not involved in the host specificity of the strains (Garrett, Crosse & Sletten, I 974).Cherry-strain mutants resistant to these phages show marked attenuation of virulence. Their resistance is due to an inability to adsorb the phage, indicating a change in the receptor-site structure (Garrett et al., 1974). Hence, receptor-site material may determine the virulence of P. morsprunorum as plum and cherry isolates adsorb the phage and are both virulent on their respective hosts.Lipopolysaccharide (LPS) of Gram-negative bacterial walls has frequently been reported as phage-receptor material (e.g. Jazwinski, Lindberg & Kornberg, 1975) and also as an endotoxin (e.g. Hawiger, Hawiger & Timmon, 1975). In view of this, lipopolysaccharide was extracted from P. morsprunorum to investigate its role in pathogenicity and as receptorsite material for phage A7 and related phages. pH 71 to which one drop of antifoam (polypropylene glycol 2000; Shell Research, Sittingbourne, Kent) was added before autoclaving. The cultures were stirred and aerated at 18 "C. Air was supplied at 500 cm3 min-l via a sintered-glass gas distribution tube (porosity 3). The purity of the cultures was tested by the Gram-stain method and by subculturing on nutrient sucrose agar (NSA; Crosse, 1959). The optimum temperature for growth of c28 is normally 25 "C but when grown in broth with efficient aeration and stirring at this temperature, cells grew to 4 to 5 times their normal length. These cells quickly reverted to the normal size when aeration was reduced and were not elongated when grown at 18 "C. Cells were harvested at the late-exponential phase using a continuous-flow centrifuge at 4 "C, and washed twice with cold distilled ...
SUMMARYA series of fungal melanoproteins (mol. wt 10,000-70,000) was isolated from culture filtrates of Venturia inaequalis, and partially characterized by gel filtration and acid hydrolysis. Petiole injection of aqueous solutions of the melanoproteins with non-phytotoxic marker compounds, into apple shoots, produced specific effects on the transport of solutes within the leaves. The effects were not reproduced by substitution of melanoprotein by egg-white lysozyme, rabbit haemoglobin, bovine serum albumen or deoxyribonuclease (EC 3. I .4.5). Inhibition of leaf expansion by injected melanoproteins was observed.The application of a melanoprotein with spore inoculum of Venturia inaequalis on to leaves of a susceptible apple variety caused a great increase in lesion development. This effect was not reproduced by the use of other proteins. The decreased lesion-stimulating activity of melanoprotein produced by V. inaequalis after storage of cultures at oo was correlated with decreased effects on solute transport in the host. Radioactive material arising from spore inoculum labelled with p4C]~~-alanine was detected in the vascular system of test plants. The distribution of this material in the infected leaf was similar to that given by petiole injection of an indicator compound with melanoprotein in healthy plants.
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