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At least 163 records · Page 9Linked to original sources
PubMed2002

Mutation of rpiA in Enterobacter cloacae decreases seed and root colonization and biocontrol of damping-off caused by Pythium ultimum on cucumber.

Strains of Enterobacter cloacae show promise as biocontrol agents for Pythium ultimum-induced damping-off on cucumber and other crops. E. cloacae A145 is a mini-Tn5 Km transposon mutant of strain 501R3 that was significantly reduced in suppression of damping-off on cucumber caused by P. ultimum. Strain A145 was deficient in colonization of cucumber, sunflower, and wheat seeds and significantly reduced in colonization of corn and cowpea seeds relative to strain 501R3. Populations of strain A145 were also significantly lower than those of strain 501R3 at all sampling times in cucumber, wheat, and sunflower rhizosphere. Populations of strain A145 were not detectable in any rhizosphere after 42 days, while populations of strain 501R3 remained at substantial levels throughout all experiments. Molecular characterization of strain A145 indicated mini-Tn5 Km was inserted in a region of the E. cloacae genome with a high degree of DNA and amino acid sequence similarity to rpiA, which encodes ribose-5-phosphate isomerase. In Escherichia coli, RpiA catalyzes the interconversion of ribose-5-phosphate and ribulose-5-phosphate and is a key enzyme in the pentose phosphate pathway. Ribose-5-phosphate isomerase activity in cell lysates from strain A145 was approximately 3.5% of that from strain 501R3. In addition, strain A145 was a ribose auxotroph, as expected for an rpiA mutant. Introduction of a 1.0-kb DNA fragment containing only the rpiA homologue into strain A145 restored ribose phosphate isomerase activity, prototrophy, seedling colonization, and disease suppression to levels similar to those associated with strain 501R3. Experiments reported here indicate a key role for rpiA and possibly the pentose phosphate pathway in suppression of damping-off and colonization of subterranean portions of plants by E. cloacae.

Cucumis sativus↗
PubMed1991

Production of the polyunsaturated fatty acids arachidonic acid and eicosapentaenoic acid by the fungus Pythium ultimum.

Several strains of species of the fungal genus Pythium, and of Phytophthora cinnamomi, were screened for content of the polyunsaturated fatty acids (PUFAs) arachidonic acid (AA) and eicosapentaenoic acid (EPA). The aim of the investigation was to establish alternative sources of these PUFAs, which are of importance in human nutrition. As a relatively prolific producer of EPA and AA, P. ultimum strain #144 was selected for a study of conditions that enhance their production over baseline levels that are present in the fungus when cultured for 6 d at 25 degrees C with rotary shaking (120 r.p.m.) in Vogel's medium containing sucrose as the carbon substrate. The levels of AA and EPA under these conditions were 133 +/- 27 and 138 +/- 25 mg l-1 (n = 5), respectively. Maximal production of these fatty acids was accomplished by the following sequence of steps. (1) Incubate the cultures for 6 d after inoculation under the conditions described above. Then (2) add glucose to the cultures (2%, w/v, final concentration) and incubate for a further 6 d at 13 degrees C. Under these conditions, the AA content of the mycelium was 205% higher than baseline levels and the EPA content was 198% higher. (3) Allow the cultures to remain stationary for 10 d which increases the AA content to 253% above baseline levels and the EPA content by 236%. Using such a procedure, 322 mg AA l-1 and 383 mg EPA 1-1 were produced.

Arachidonic Acid↗
PubMed2003

Surface motility in Pseudomonas sp. DSS73 is required for efficient biological containment of the root-pathogenic microfungi Rhizoctonia solani and Pythium ultimum.

Pseudomonas sp. DSS73 was isolated from the rhizoplane of sugar beet seedlings. This strain exhibits antagonism towards the root-pathogenic microfungi Pythium ultimum and Rhizoctonia solani. Production of the cyclic lipopeptide amphisin in combination with expression of flagella enables the growing bacterial culture to move readily over the surface of laboratory media. Amphisin is a new member of a group of dual-functioning compounds such as tensin, viscosin and viscosinamid that display both biosurfactant and antifungal properties. The ability of DSS73 to efficiently contain root-pathogenic microfungi is shown to arise from amphisin-dependent surface translocation and growth by which the bacterium can lay siege to the fungi. The synergistic effects of surface motility and synthesis of a battery of antifungal compounds efficiently contain and terminate growth of the microfungi.

Antibiosis↗
PubMed2002

High-level production of gamma-linolenic acid in Brassica juncea using a delta6 desaturase from Pythium irregulare.

gamma-Linolenic acid (GLA), a nutritionally important fatty acid in mammals, is synthesized by a delta6 desaturase. Here, we report identification of PiD6, a new cDNA from the oleaginous fungus, Pythium irregulare, encoding a 459-amino acid protein that shares sequence similarity to carboxyl-directed desaturases from various species. Expression of PiD6 in yeast (Saccharomyces cerevisiae) revealed that it converts exogenously supplied linoleic acid into GLA, indicating that it encodes a delta6 fatty acid desaturase. Expression of the desaturase in Brassica juncea under the control of the Brassica napus napin promoter resulted in production of three delta6 unsaturated fatty acids (18:2-6, 9; 18:3-6, 9, 12; and 18:4-6, 9, 12, 15) in seeds. Among them, GLA (18:3-6, 9, 12) is the most abundant and accounts for up to 40% of the total seed fatty acids. Lipid class and positional analysis indicated that GLA is almost exclusively incorporated into triacylglycerol (98.5%) with only trace amounts found in the other lipids. Within triacylglycerols, GLA is more abundant at the sn-2 position.

Amino Acid Sequence↗
PubMed2000

Crystallization and preliminary X-ray studies of oligandrin, a sterol-carrier elicitor from Pythium oligandrum.

Oligandrin is a 10 kDa acidic protein produced by the fungus micromycete Pythium oligandrum and is a member of the alpha-elicitin group, with sterol- and lipid-carrier properties. Oligandrin has been crystallized at 290 K using PEG 4000 as a precipitant. A cholesterol complex was obtained under the same conditions. The space group of the crystals at low temperature (100 K) is C222, with unit-cell parameters a = 94.0, b = 171.1, c = 55.3 A. Four molecules are present in the asymmetric unit. Data from the free and cholesterol-complexed forms were recorded at synchrotron sources to resolutions of 2.4 (uncomplexed) and 1.9 A (complexed), respectively.

Carrier Proteins↗
PubMed1976

Ultrastructure and chemical analysis of the cell wall of Pythium debaryanum.

The ultrastructure and component polysaccharides of the cell wall of Pythium debaryanum IFO-5919 were investigated. From results obtained by means of acid, alkali, Schweitzer reagent and beta-1, 3-glucanase treatments and electron microscopy, it was concluded that 1) the acid-extracted fraction was a 1,3-linked branched glucan, 2) the alkali-extranded fraction was a mixture of 1,3-, 1,6-, and 1,3,6-linked highly branched two glucans, 3) the Schweitzer reagent-extracted fraction was a beta-1, 4-linked glucan, 4) the cell wall was constructed from two types of cullulosic microfibrils, as a frame and as a finer network, and amorphous beta-1, 3-glucan including beta-1, 6-linkage, 5) cellulosic microfibrils were covered by matrix material consisting of a mixture of amorphous beta-1, 3-linked and beta-1, 6-linked branching glucans.

Cell Wall↗
PubMed1997

Pythium insidiosum keratitis.

A case of Pythium insidiosum keratitis is described. It is an unusual organism that is difficult to isolate. Cases in animals and humans have been reported from tropical and subtropical parts of the world but this is the first case from a temperate region and was acquired from a hot pool. Although resembling a fungus, it is insensitive to all antifungals and requires wide surgical excision for cure.

Adult↗
PubMed2001

A new species of Pythium with filamentous sporangia having pectinolytic activities, isolated in the Burgundy region of France.

A new species, Pythium pectinolyticum (F-83.1), isolated from soil samples taken in the Burgundy region is being described here. This species is characterised by its filamentous non-inflated type of sporangia, smooth-walled mostly catenulate oogonia and very rare antheridia. This fungus is a very slow-growing organism on most of the solid media, but it grows well in liquid media and also on those containing pectin as the sole source of carbon. Morphological features are described here together with the sequences of the internal transcribed spacer 1 region of the nuclear ribosomal DNA of the fungus, its comparison with related species, and its pectinolytic behaviour.

Base Sequence↗
PubMed2002

ITS1 region of the rDNA of Pythium proliferatum, a new species: its taxonomy and its comparison with related species.

A new species, Pythium proliferatum (F-382), was isolated from soil samples taken in Genlis in the burgundian region of France. The fungus is unique because of the character combinations of its large, spherical to elongated, proliferating sporangia, and its smooth walled oogonia supplied with different types of antheridia like hypogynous, monoclinous sessile, monoclinous stalked, diclinous and wrapping around the oogonia. Almost all types of antheridia that are found in the genus are present in this new species. Morphological features of this new species, together with the sequences of the ITS1 region of its nuclear ribosomal DNA and its comparison with related species are discussed in this article.

Base Sequence↗
PubMed2002

Identification to the species level of the plant pathogens Phytophthora and Pythium by using unique sequences of the ITS1 region of ribosomal DNA as capture probes for PCR ELISA.

The ribosomal internal transcribed spacer 1 region was sequenced for 10 species of Pythium and eight species of Phytophthora. Alignment of the sequences revealed considerable sequence microheterogeneity, which was utilized to prepare a capture probe of unique sequence for each species. The capture probes were tested by PCR ELISA, combining the sensitivity and specificity of the polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). The probes were entirely species specific, enabling the detection and identification of the amplified DNA of species from individual cultures or from mixed samples of the DNAs of two different species. This approach to species identification, which provides a molecular technology to process large numbers of samples and still identify the fungi with a high level of confidence, may greatly reduce the resources and the time of highly trained specialists currently needed to identify these important species of plant pathogenic fungi.

Base Sequence↗
PubMed2002

ITS region of Pythium canariense sp. nov., its morphology and its interaction with Botrytis cinerea.

A new species Pythium canariense (CI-07), isolated from soil samples taken in the San Nicolas region of the Canary islands (Gran Canaria, Spain), is being described here. This species is characterised by its spherical to pyriform, intercalary to catenulate sporangia, smooth-walled terminal oogonia supplied with monoclinous and diclinous antheridia which at times are branched and wrap around the female gametangia. The fungus has an antagonistic effect on Botrytis cinerea, the grey mould fungus. Morphological features are being given here together with the sequence of the complete internal transcribed spacer region of the nuclear ribosomal DNA of the fungus, its comparison with related species, and some aspects of its antagonistic behaviour with B. cinerea.

Antibiosis↗
PubMed2002

Regulatory role of external calcium on Pythium porphyrae (Oomycota) zoospore release, development and infection in causing red rot disease of Porphyra yezoensis (Rhodophyta).

Formation of zoosporangia and cleavage of zoosporangial cytoplasm to zoospores in Pythium porphyrae is absolutely dependent on extracellular calcium. Calcium ion could be substituted neither by monovalent nor divalent cations tested. Increased concentrations of extracellular calcium did not affect the release of zoospores from zoosporangia but inhibited the zoospore motility. Chelating calcium ion by EGTA has decreased the ability of encysted zoospores to germinate and form appressoria. The increased external calcium-ion concentration has decreased the infectivity of Porphyra yezoensis thalli in a linear fashion apparently indicating a role of calcium in the signaling mechanism.

Animals↗
PubMed2006

Antagonism of Pythium blight of zucchini by Hypocrea jecorina does not require cellulase gene expression but is improved by carbon catabolite derepression.

Toward a better understanding of the biochemical events that lead to biocontrol of plant pathogenic fungi by Hypocrea/Trichoderma spp., we investigated the importance of carbon catabolite (de)repression and cellulase formation in the antagonization of Pythium ultimum by Hypocrea jecorina (Trichoderma reesei) on agar plates and in planta. Hypocrea jecorina QM9414 could antagonize and overgrow P. ultimum but not Rhizoctonia solani in plate confrontation tests, and provided significant protection of zucchini plants against P. ultimum blight in planta. A carbon catabolite derepressed cre1 mutant of H. jecorina antagonized P. ultimum on plates more actively and increased the survival rates of P. ultimum-inoculated zucchini plants in comparison with strain QM9414. A H. jecorina mutant impaired in cellulase induction could also antagonize P. ultimum on plates and provided the same level of protection of zucchini plants against P. ultimum as strain QM9414 did. We conclude that cellulase formation is dispensable for biocontrol of P. ultimum, whereas carbon catabolite derepression increases the antagonistic ability by apparently acting on other target genes.

Carbon↗
PubMedDate not supplied

Esophagitis due to Pythium insidiosum infection in two dogs.

Chronic esophagitis due to Pythium insidiosum infection caused weight loss, dysphagia, and hypersalivation in 2 dogs from rural Tennessee. Although dog 1 presented for evaluation in December 1984 and dog 2 in October 1992, infection likely occurred during the previous summer by drinking fresh pond water containing zoospores. Hematologic testing revealed eosinophilia and hypergammaglobulinemia in one dog. An etiologic diagnosis was not made until postmortem evaluation when hyphae within necrotic and granulomatous cellular infiltrates in the esophageal wall were identified as P insidiosum by immunoperoxidase staining. Failure to culture the organism from the esophageal wall in dog 2 was attributed to refrigeration of the tissues, since refrigeration decreases the survivability of P insidiosum.

Animals↗
PubMed1990

Induction of zoospore formation in Thai isolates of Pythium insidiosum.

Three human isolates of Pythium insidiosum De Cock 1987, the aetiologic agent of pythiosis, were induced for zoosporogenesis. The isolates were grown on Sabouraud glucose agar for 2 days before being inoculated into boiled spikelets of Axonopus compressus (Gramineae) and then into induction medium (IM). Optimum zoospore formation was demonstrated under the light microscope after incubation for 24 h at 37 degrees C in IM.

Culture Media↗
PubMed1986

Characterization of an antibiotic produced by a strain of Pseudomonas fluorescens inhibitory to Gaeumannomyces graminis var. tritici and Pythium spp.

The production, isolation, and characterization of an antibiotic substance from cultures of Pseudomonas fluorescens 2-79 (NRRL B-15132) is described. P. fluorescens 2-79 originally was isolated from the roots of wheat and is suppressive to the wheat root disease take-all caused by Gaeumannomyces graminis var. tritici. The antibiotic was isolated from potato glucose broth cultures of strain 2-79 by solvent extraction. It was purified by silica gel column chromatography and was a greenish yellow, needle-shaped crystal with a melting point of 242 degrees C (decomposition). It was soluble in methylene chloride, chloroform, acetone, 2 N sodium hydroxide, and 2 N hydrochloric acid and was insoluble in water, methanol, ethyl acetate, tetrahydrofuran, diethyl ether, carbon tetrachloride, hexane, and petroleum ether. On the basis of UV, infrared, 1H-nuclear magnetic resonance, 13C-nuclear magnetic resonance, mass spectral analysis, and elemental analysis, the structure of the antibiotic is proposed to be a dimer of phenazine carboxylic acid. Lithium aluminum hydride reduction of the antibiotic yielded hydroxymethyl phenazine as a major product which retained most of the biological characteristics of the parent molecule. There were no toxic symptoms when mice received this antibiotic by oral doses up to 464 mg/kg. The antibiotic showed excellent activity against several species of fungi, including the wheat pathogens Gaeumannomyces graminis var. tritici, Rhizoctonia solani, and Pythium aristosporum; and it may have a role in suppression of take-all in vivo by strain 2-79.

Aluminum↗
PubMed2006

Tvbgn3, a beta-1,6-glucanase from the biocontrol fungus Trichoderma virens, is involved in mycoparasitism and control of Pythium ultimum.

Even though beta-1,6-glucanases have been purified from several filamentous fungi, the physiological function has not been conclusively established for any species. In the present study, the role of Tvbgn3, a beta-1,6-glucanase from Trichoderma virens, was examined by comparison of wild-type (WT) and transformant strains in which Tvbgn3 was disrupted (GKO) or constitutively overexpressed (GOE). Gene expression analysis revealed induction of Tvbgn3 in the presence of host fungal cell walls, indicating regulation during mycoparasitism. Indeed, while deletion or overexpression of Tvbgn3 had no evident effect on growth and development, GOE and GKO strains showed an enhanced or reduced ability, respectively, to inhibit the growth of the plant pathogen Pythium ultimum compared to results with the WT. The relevance of this activity in the biocontrol ability of T. virens was confirmed in plant bioassays. Deletion of the gene resulted in levels of disease protection that were significantly reduced from WT levels, while GOE strains showed a significantly increased biocontrol capability. These results demonstrate the involvement of beta-1,6-glucanase in mycoparasitism and its relevance in the biocontrol activity of T. virens, opening a new avenue for biotechnological applications.

Amino Acid Sequence↗