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PubMed2002

Bacteria associated with hazelnut (Corylus avellana L.) decline are of two groups: Pseudomonas avellanae and strains resembling P. syringae pv. syringae.

A total of 118 fluorescent pseudomonads associated with hazelnut decline, which has been occurring for many years in different areas of northern Greece and Italy, were assessed by performing a repetitive PCR analysis with enterobacterial repetitive intergenic consensus, box element, and repetive extragenic palindromic primer sets, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell protein extracts, a carbon compound utilization analysis, and an analysis to determine the presence of the syrB gene. A subset of 53 strains was also characterized by amplified 16S ribosomal DNA restriction analysis (ARDRA) by using nine restriction endonucleases. The virulence of 40 representative strains was assessed by using serial doses. The pathogenic specificities of the strains were also verified. ARDRA carried out with HinfI revealed two main groups of strains, groups A and B, which exhibited a level of similarity of 57%. The other eight restriction endonucleases used did not separate the strains. In addition, a cluster analysis performed by the unweighted pair group method using arithmetic averages after repetitive PCR and SDS-PAGE of protein extracts also revealed the same two groups. Furthermore, the differential utilization of some carbon compounds made it possible to differentiate the groups. Virulence assessment clearly indicated that the group A strains are very virulent, whereas the group B strains proved to be mildly virulent for hazelnut. Group A included the strains isolated in northern Greece and central Italy (i.e., the province of Viterbo); these strains do not have the syrB gene, are pathogenically restricted to Corylus avellana, and belong to Pseudomonas avellanae. Group B includes the other strains obtained from hazelnut cultivated in Piedmont, Campania, Latium, Sicily, and Sardinia. They represent a distinct taxon closely related to Pseudomonas syringae pv. syringae.

Bacterial Proteins↗
PubMed1985

Isolation and characterization of Tn5 insertion mutants of Pseudomonas syringae pv. syringae altered in the production of the peptide phytotoxin syringotoxin.

A syringotoxin-producing strain of Pseudomonas syringae pv. syringae (B457) was subjected to Tn5 mutagenesis by the transposon vector pSUP1011. Analyses of auxotrophs obtained suggested simple random insertions of Tn5. Syringotoxin-negative mutants arose at a frequency of about 0.28%. In a Southern blot analysis, the loss of toxin production was associated with Tn5 insertions into chromosomal EcoRI fragments of about 10.5, 17.8, and 19.3 kilobases. Data from a Southern blot analysis of SstI-digested DNA from these mutants suggest that the 10.5- and 17.8-kilobase EcoRI fragments may be adjacent to or near each other. Mutants that produced only 3 to 4% wild-type toxin levels also were identified.

Bacterial Toxins↗
PubMed1988

Molecular analysis of a pathogenicity locus in Pseudomonas syringae pv. syringae.

One of the chromosomal regions of Pseudomonas syringae pv. syringae encoding pathogenicity factors had been mapped into a 3.9-kilobase-pair fragment in previous studies. Promoter probe analysis indicated the existence of a promoter near one end of the fragment. DNA sequencing of this fragment revealed the existence of a consensus promoter sequence in the region of the promoter activity and two open reading frames (ORFs) downstream. These ORFs, ORF1 and ORF2, encoded putative polypeptides of 40 and 83 kilodaltons, respectively. All ORF1::Tn5 as well as ORF2::Tn5 mutant strains were nonpathogenic on susceptible host bean plants and were unable to elicit hypersensitive reactions on nonhost tobacco plants. The deduced amino acid sequence of the 83-kilodalton polypeptide contained features characteristic of known integral membrane proteins. Fusion of the lacZ gene to ORF2 led to the expression of a hybrid protein inducible in Escherichia coli. The functions of the putative proteins encoded by ORF1 and ORF2 are unknown at present.

Amino Acid Sequence↗
PubMed1988

Physical and functional analyses of the syrA and syrB genes involved in syringomycin production by Pseudomonas syringae pv. syringae.

The syrA and syrB genes involved in syringomycin production in Pseudomonas syringae pv. syringae B301D were identified from an EcoRI-pLAFR3 cosmid library and then physically and functionally analyzed in relation to plant pathogenicity. Homologous recombination of the genes required for syringomycin production from cosmids pGX183 (syrA) and pGX56 (syrB), respectively, introduced into nontoxigenic (Tox-) Tn5 mutants W4S2545 and W4S770 resulted in the concomitant restoration of toxin production and full virulence. The disease indices of the Tox+ strains obtained by recombination of the cloned, homologous DNA into the corresponding Tn5 mutant were essentially equivalent to that of strain B301D-R and significantly higher than those of W4S2545 and W4S770. A 12-kilobase (kb) EcoRI fragment from pGX183 was subcloned (i.e., pGX15) and found to contain the sequences necessary for syringomycin production. A map of pGX15 prepared by a combination of restriction endonuclease digestions and Tn5 mutagenesis showed that the syrA sequence was 2.3 to 2.8 kb. Marker exchange of syrA::Tn5 from pGX15 into B301D-R yielded nonpathogenic phenotypes, indicating that syrA is a regulatory gene since it is necessary for both syringomycin production and pathogenicity. The 4.9-kb EcoRI fragment from pGX56 was subcloned (i.e., pGX4) and shown to carry the syrB sequence which was 2.4 to 3.3 kb. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of protein extracts from B301D-R associated five proteins, ranging from approximately 130,000 to approximately 470,000 in molecular weight, with syringomycin production. The syrA and syrB genes were required for the formation of proteins SR4 (approximately 350,000) and SR5 (approximately 130,000), which are believed to be components of the syringomycin synthetase complex.

Bacterial Proteins↗
PubMed1990

Construction of a stable shuttle vector for high-frequency transformation in Pseudomonas syringae pv. syringae.

A cryptic 80.3-kilobase plasmid, pOSU900, in Pseudomonas syringae pv. syringae strain J900 could be cured by treatment with mitomycin without affecting the pathogenicity of J900 on the host, Phaseolus vulgaris L. The replication region of pOSU900 was identified, subcloned, and modified for construction of a high-copy cloning vector. This vector could be transformed into Pseudomonas strains with high efficiency (ca. 10(6) transformants per microgram of DNA) and was very stable during growth of the host bacteria in planta.

Cloning, Molecular↗
PubMed1995

Analysis of the syrB and syrC genes of Pseudomonas syringae pv. syringae indicates that syringomycin is synthesized by a thiotemplate mechanism.

The syrB and syrC genes are required for synthesis of syringomycin, a lipodepsipeptide phytotoxin produced by Pseudomonas syringae pv. syringae, and are induced by plant-derived signal molecules. A 4,842-bp chromosomal region containing the syrB and syrC genes of strain B301D was sequenced and characterized. The open reading frame (ORF) of syrB was 2,847 bp in length and was predicted to encode an approximately 105-kDa protein, SyrB, with 949 amino acids. Searches of databases revealed that SyrB shares homology with members of a superfamily of adenylate-forming enzymes involved in peptide antibiotic and siderophore synthesis in a diverse spectrum of microorganisms. SyrB exhibited the highest degree of overall similarity (56.4%) and identity (33.8%) with the first amino acid-activating domain of pyoverdin synthetase, PvdD, of Pseudomonas aeruginosa. The N-terminal portion of SyrB contained a domain of approximately 600 amino acids that resembles the amino acid-activating domains of thiotemplate-employing peptide synthetases. The SyrB domain contained six signature core sequences with the same order and spacing as observed in all known amino acid-activating domains involved in nonribosomal peptide synthesis. Core sequence 6 of SyrB, for example, was similar to the binding site for 4'-phosphopantetheine, a cofactor required for thioester formation. The syrC ORF (1,299 bp) was located 175 bp downstream of the syrB ORF. Analysis of the transcriptional and translational relationship between the syrB and syrC genes demonstrated that they are expressed independently. The syrC ORF was predicted to encode an approximately 48-kDa protein product of 433 amino acids which is 42 to 48% similar to a number of thioesterases, including fatty acid thioesterases, haloperoxidases, and acyltransferases, that contain a characteristic GXS (C) XG motif. In addition, a zinc-binding motif was found near the C terminus of SyrC. The data suggest that SyrB and SyrC function as peptide synthetases in a thiotemplate mechanism of syringomycin biosynthesis.

Amino Acid Sequence↗
PubMed1997

Altered localization of HrpZ in Pseudomonas syringae pv. syringae hrp mutants suggests that different components of the type III secretion pathway control protein translocation across the inner and outer membranes of gram-negative bacteria.

Pseudomonas syringae pv. syringae 61 (Pss61) secretes the HrpZ harpin by a type III protein secretion pathway encoded by a cluster of hrp (hypersensitive response and pathogenicity) and hrc genes. The nine hrc genes represent a subset of hrp genes that are also conserved in the type III virulence protein secretion systems of animal pathogenic Yersinia, Shigella, and Salmonella spp. The hrpJ and hrpU operons contain seven hrc genes (counting hrcQ(A) and hrcQ(B) as one gene), all with additional homologs involved in flagellar biogenesis and secretion, and five of which encode predicted inner membrane proteins. The hrpC and hrpZ operons encode HrcC and HrcJ, respectively, which are associated with the outer membrane. Interposon mutants affected in all of the hrc genes in the hrpJ and hrpU operons and TnphoA-induced hrcC and hrcJ mutants were assayed for altered localization of HrpZ in mid-log-phase cultures by immunoblotting sodium dodecyl sulfate-polyacrylamide gels that were run with various cell fractions. The hrpJ and hrpU operon mutants revealed a novel phenotype of partially reduced accumulation of HrpZ in the total culture (despite wild-type levels of hrpZ operon transcription), all of which was cell bound and equivalent in level to that of cell-bound HrpZ in the wild type. The hrcC and hrcJ mutant cultures accumulated the same total amount of HrpZ as the wild type, but the HrpZ was cell bound. Among all the strains tested, only the hrcC mutant accumulated significant amounts of HrpZ in the periplasm, as indicated by selective release through spheroplasting. Analysis of nonpolar mutations in the hrpU and hrpC operons support the results obtained with polar mutations. These observations indicate that a constant pool of HrpZ is maintained in the cytoplasm of Pss61 despite secretion deficiencies, that the hrpJ and hrpU operons encode an alternative to the Sec (general protein export) pathway for translocation across the inner membrane, that genes in the hrpC operon are necessary for translocation across the outer membrane, and that the Pss61 Hrp system permits study of two genetically distinguishable stages in type III protein secretion.

Bacterial Outer Membrane Proteins↗
PubMed1999

Cellular locations of Pseudomonas syringae pv. syringae HrcC and HrcJ proteins, required for harpin secretion via the type III pathway.

The complete hrp-hrc-hrmA cluster of Pseudomonas syringae pv. syringae 61 encodes 28 polypeptides. A saprophytic bacterium carrying this cluster is capable of secreting HrpZ-a harpin encoded by hrpZ-in an hrp-dependent manner, which suggests that this cluster contains sufficient components to assemble functional type III secretion machinery. Sequence data show that HrcJ and HrcC are putative outer membrane proteins, and nonpolar mutagenesis demonstrates they are all required for HrpZ secretion. In this study, we investigated the cellular localization of the HrcC and HrcJ proteins by Triton solubilization, sucrose-gradient isopycnic centrifugation, and immunogold labeling of the bacterial cell surface. Our results indicate that HrcC is indeed an outer membrane protein and that HrcJ is located between both membranes. Their membrane localization suggests that they might be involved in the formation of a supramolecular structure for protein secretion.

Bacterial Outer Membrane Proteins↗
PubMed2002

[Activity of toxins produced by Pseudomonas syringae pv. syringae in model and cell membranes].

We studied effects of toxins produced by a bacterium Pseudomonas syringae pv. syringae on the conductance of bilayer lipid membranes (BLM). The used toxins were as follows: syringopeptin 22A (SP22A), syringomycin E (SPE), syringostatin A (SSA), syringotoxin B (STB), and methylated syringomycin E (CH3-SRE). All toxins demonstrated channel-forming activity. The threshold sequence for toxin activity was SP22A > SRE approximately equal to SSA > STB > CH3-SRE, and this sequence was independent of lipid membrane composition, and NaCl concentration (pH 6) in the membrane bathing solution (in the range of 0.1-1.0 M). This sequence correlated with relative bioactivities of toxins. In addition, SRE demonstrated a more potent antifungal activity than CH3-SRE. These findings suggest that ion channel formation may underlie the bioactivities of the above toxins. The properties of single ion channels formed by the toxins in BLMs were found to be similar, which points to the similarity in the channel structures. In negatively charged membranes, bathed with diluted electrolyte solutions (0.1 M NaCl), the channels were seen to open with positive transmembrane potentials (V) (from the side of toxin addition), and close with negative potentials. In uncharged membranes the opposite response to a voltage sign was observed. Increasing the NaCl concentration up to 1 M unified the voltage sensitivity of channels in charged and uncharged membranes: channels opened with negative V, and closed with positive V. With all systems, the voltage current curves of single channels were similarly superlinear in the applied voltage and asymmetric in its sign. It was found that the single channel conductance of STB and SSA was higher than that of other toxin channels. All the toxins formed at least two types of ion channels that were multiple by a factor of either 6 or 4 in their conductance. The results are discussed in terms of the structural features of toxin molecules.

Antifungal Agents↗
PubMedDate not supplied

Effect of ten antibiotics on the recovery of seed-borne Pseudomonas syringae pv syringae of cowpea, Vigna unguiculata (L.) Walp var. IT 825-2246-4.

The effect of ten different antibiotics: Amoxil, Ampicillin, Chloramphenicol, Cloxacillin, Cotrimexazole, Erythromycin, Nitrofurantoin, Penicillin, Tetracycline and Vibramycin on the recovery of seed-borne Pseudomonas syringae pv. syringae and on percentage seed germination of cowpea, Vigna unguiculata(L.) Walp var. IT 825-2246-4 at various temperature regimes: 25 degrees C, 30 degrees C, 35 degrees C and 40 degrees C were investigated using the Standard Blotter Method. Seeds were presoaked for 1 hour in each antibiotic at the concentration rate of 250mg/liter before plating on three layers of moist blotter papers in petri dishes. Seeds were incubated for 72 hours in temperature controlled incubators at the various temperature regimes. Seeds not treated with antibiotic served as control. In all the temperature regimes studied. Tetracycline was the most effective antibiotic in controlling the bacterium while Cotrimexazole was the least effective when compared with control. The highest percentage seed germination was recorded on seeds treated with Amoxil while the lowest percentage seed germination was recorded on seeds treated with Tetracycline. Generally, the temperature regimes used did not have any appreciable effect on the recovery of the bacterium and on percentage seed germination.

Anti-Bacterial Agents↗
PubMed2004

Synthesis of a D-rhamnose branched tetrasaccharide, repeating unit of the O-chain from Pseudomonas syringae pv. Syringae (cerasi) 435.

The first synthesis of a d-rhamnose branched tetrasaccharide, corresponding to the repeating unit of the O-chain from Pseudomonas syringae pv. cerasi 435, as methyl glycoside is reported. The approach used is based on the synthesis of an opportune building-block, that is the methyl 3-O-allyl-4-O-benzoyl-alpha-D-rhamnopyranoside, which was then converted into both a glycosyl acceptor and two different protected glycosyl trichloroacetimidate donors. Successive couplings of these three compounds afforded the target oligosaccharide. The reported synthesis is also useful to perform the oligomerization of the repeating unit.

Carbohydrate Conformation↗
PubMed2003

Studies on the constituents of Syringa species. XII. New glycosides from the leaves of Syringa reticulata (BLUME) HARA.

Three new glycosides, 6'-O-alpha-D-galactopyranosylsyringopicroside (1), secologanoside 7-methyl ester (2) and (+)-lariciresinol 4'-O-beta-D-glucopyranosyl-(1-->3)-beta-D-glucopyranoside (3), were isolated from the leaves of Syringa reticulata. Their structures were established on the basis of chemical and spectral data. Compound 1 is the first naturally occurring iridoid di-glycoside having melibiose. Comparison of the spectral data of 2 and that previously recognized as secologanoside 7-methyl ester led to the conclusion that the recognized structure should be revised to the sodium salt of secoxyloganin (2').

Glycosides↗
PubMed2002

The phytotoxic lipodepsipeptide syringopeptin 25A from Pseudomonas syringae pv syringae forms ion channels in sugar beet vacuoles.

Syringopeptin 25A (SP(25)A) belongs to a family of cyclic lipodepsipeptides (LDPs) produced by the gram-negative bacterium Pseudomonas syringae, a phytopathogenic organism that affects several plants of agronomic interest. LDPs increase the permeability of plasma and, possibly, intracellular membranes in plant cells. Consistently, SP(25)A forms ion channels in planar lipid bilayers and other model membranes. Here we used sugar beet tonoplasts as a new biological model system to study toxin action. When applied to the vacuoles by a fast perfusion procedure, SP(25)A increases membrane permeability by forming discrete ion channels even at low applied potentials. The SP(25)A channel displays anion selectivity (with a Cl-/K+ permeability ratio of 6.7 +/- 1.3) and has intrinsic rectification properties that derive from a different channel conductance at negative and positive voltages, presumably owing to an asymmetric distribution of fixed charges on the pore. Substitution of chloride with different anions reveals the following selectivity sequence NO3- approximately Cl-> F- > gluconate-, suggesting that the permeation pore is filled with water. The properties of the SP(25)A channels in vacuolar membranes are similar to those observed in planar lipid membranes prepared with asolectin. This work provides a direct demonstration of toxin effects on a native plant membrane, extending to a biological system previous results obtained on artificial planar lipid membranes.

Bacterial Toxins↗
PubMed2002

Studies on the constituents of Syringa species. X. Five new iridoid glycosides from the leaves of Syringa reticulata (Blume) Hara.

Five new iridoid glycosides, (8Z)-ligstroside (1), (8Z)-nüzhenide (3), 6'-O-alpha-D-glucopyranosylsyringopicroside (4), 3'-O-beta-D-glucopyranosylsyringopicroside (5) and 4'-O-beta-D-glucopyranosylsyringopicroside (6) were isolated, together with a known one, (8E)-nüzhenide (2), from the leaves of Syringa reticulata. Their structures were established on the basis of chemical and spectral data. Compounds 1 and 3 are the first findings of a (8Z)-oleoside-type secoiridoid. Compound 4 is the first naturally occurring iridoid di-glycoside having an isomaltose.

Iridoids↗
PubMed2000

Membrane-permeabilizing activities of cyclic lipodepsipeptides, syringopeptin 22A and syringomycin E from Pseudomonas syringae pv. syringae in human red blood cells and in bilayer lipid membranes.

The pore-forming activities of cyclic lipodepsipeptides (CLPs), syringopeptin 22A (SP22A) and syringomycin E (SRE) were compared on the human red blood cell (RBC) membrane and on bilayer lipid membranes (BLMs). SP22A above a concentration of 4 x 10(5) molecules/cell significantly increased the RBC membrane permeability for 86Rb. With electric current measurements on BLM, it was proved that like SRE, the SP22A formed two types of ion channels in the membrane, small and large, the latter having six times larger conductance and longer dwell time. Both CLPs formed clusters consisting of six small channels, and the channel-forming activity of SP22A is about one order of magnitude higher than that of SRE. A Hill coefficient of 2-3 estimated from the concentration dependence of these CLPs-induced lysis gave a proof of the pore oligomerization on RBCs. Transport kinetic data also confirmed that SP22A pores were oligomers of at least three monomers. While SRE pores were inactivated in time, no pore inactivation was observed with SP22A. The 86Rb efflux through SP22A-treated RBCs approached the tracer equilibrium distribution with a constant rate; a constant integral current was measured on the BLM for as long as 2.5 h as well. The partition coefficient (Kp = 2 x 10(4) l/mol) between the RBC membrane and the extracellular space was estimated for SRE to be at least six times higher than that for SP22A. This finding suggested that the higher ion permeability of the SP22A-treated cells compared to that of SRE was the result of the higher pore-forming activity of SP22A.

Cell Membrane Permeability↗
PubMed1999

Conductive properties and gating of channels formed by syringopeptin 25A, a bioactive lipodepsipeptide from Pseudomonas syringae pv. syringae, in planar lipid membranes.

Syringopeptin 25A, a pseudomonad lipodepsipeptide, can form ion channels in planar lipid membranes. Pore conductance is around 40 pS in 0.1 M NaCl. Channel opening is strongly voltage dependent and requires a negative potential on the same side of the membrane where the toxin was added. These pores open and close with a lifetime of several seconds. At negative voltages, an additional pore state of around 10 pS and a lifetime of around 30 ms is also present. The voltage dependence of the rates of opening and closing of the stable pores is exponential. This allows estimation of the equivalent charge that is moved across the membrane during the process of opening at about 2.6 elementary charges. When NaCl is present, the pore is roughly 3 times more permeant for anions than for cations. The current voltage characteristic of the pore is nonlinear, i.e., pore conductance is larger at negative than at positive voltages. The maximal conductance of the pore depends on the concentration of the salt present, in a way that varies almost linearly with the conductivity of the solution. From this, an estimate of a minimal pore radius of 0.4 nm was derived.

Amino Acid Sequence↗