| 1. |
- Olsson, Pål Axel, et al.
(författare)
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The use of phospholipid and neutral lipid fatty acids to estimate biomass of arbuscular mycorrhizal fungi in soil
- 1995
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Ingår i: Mycological Research. - 0953-7562. ; 99:5, s. 623-629
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Tidskriftsartikel (refereegranskat)abstract
- Cucumber seedlings associated with the arbuscular mycorrhizal (AM) fungi Glomus WUM10 or G. caledanium (BEG 15) were grown in PVC tubes with a lateral root-free compartment and an identical compartment containing both hyphae and roots. The amounts of specific fatty acids, in the neutral lipid and phospholipid fractions, were measured in both compartments and compared with controls without mycorrhiza. The phospholipid fatty acids (PLFAs) 16:1 omega 5, 18:1 omega 7c, 20:4 and 20:5 were present in higher amounts in soil with mycorrhizal hyphae than in soil without mycorrhizal hyphae. The largest relative difference was found in 20:5, but a good correlation existed between 16:1 omega 5 and 20:5 in soil with hyphae. Amounts of these fatty acids were correlated both with length of mycorrhizal hyphae and with amounts of ATP in soil. Conversion factors to calculate hyphal length and AM fungal biomass carbon using the phospholipid fatty acids could thus be estimated; 38 nmol PLFA 16:1 omega 5 mg(-1) AM fungal biomass C (Glomus WUM10) and 22 nmol PLFA 20:5 mg(-1) biomass C. The fatty acid 16:1 omega 5 from the neutral lipid fraction, containing triglycerides, dominated in soils with mycorrhizal hyphae. The amount of 16:1 omega 5 in the neutral lipid fraction decreased during storage of soils, indicating a decrease in storage lipids, while the proportion of 16:1 omega 5 in the phospholipid fraction was almost unaffected.
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| 2. |
- Tunlid, Anders, et al.
(författare)
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Fungal attachment to nematodes
- 1992
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Ingår i: Mycological Research. - 0953-7562. ; 96:6, s. 401-412
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Forskningsöversikt (refereegranskat)abstract
- The adhesion mechanisms in three nematophagous fungi are reviewed. In all these fungi the infection and subsequent digestion of nematodes is initiated by the firm adhesion of the fungus to the nematode surface. In Arthrobotrys oligospora the adhesive phase is restricted to special three-dimensional structures. Drechmeria coniospora conidia attach to the nematode cuticle by an adhesive bud while Catenaria anguillulae uses an adhesive phase of zoospore development for this purpose. In A. oligospora, the adhesion of nematodes to the traps is mediated by a layer of extracellular fibrillar polymers. The ultrastructure of this layer changes during adhesion, the fibrils become more dense and oriented in one direction. The surface layer consists mainly of carbohydrate-containing fibrils and a low-molecular-weight protein. Previous and present studies show that the low-molecular-weight protein of A. oligospora is a lectin. In contrast, the adhesive layer of D. coniospora does not seem to change during the adhesion process. The adhesin of C. anguillulae appears to consist mainly of protein. The studies suggest that adhesion of nematodes to A. oligospora involves a recognition event using a lectin-carbohydrate interaction which might trigger the reorganization of the surface polymer layer and release of enzymes, leading to the firm binding of the nematode. A similar process may take place also in other nematophagous fungi.
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| 3. |
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| 4. |
- Ahrén, Dag, et al.
(författare)
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Low genetic diversity among isolates of the nematode-trapping fungus Duddingtonia flagrans: evidence for recent worldwide dispersion from a single common ancestor
- 2004
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Ingår i: Mycological Research. - 0953-7562. ; 108, s. 1205-1214
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Tidskriftsartikel (refereegranskat)abstract
- The genetic variation of Duddingtonia flagrans, which has become a promising biocontrol agent of animal parasitic nematodes, was investigated in a worldwide collection of 22 isolates. We analysed the sequence variation in four nuclear genes, tubA (beta-tubulin), CMD1 (calmodulin), EF1alpha (translation elongation factor 1alpha), and PII (extracellular serine protease). 1428 aligned base pairs (bp) were analysed from the four genes, including 709 bp of introns. In addition, the variations in three anonymous genomic regions comprising 1155 bp were examined. Three single nucleotide polymorphisms (SNPs) were detected in the seven loci, none of them in the protein encoding genes. The genetic variation was significantly higher in the nematode-trapping fungus Arthrobotrys oligospora, the closest evolutionary relative to D. flagrans. Analysis of 12 isolates of A. oligospora revealed 30 SNPs in tub A, CMD1, EF1alpha and PII. The genetic variation in the isolates of D. flagrans was further examined using AFLP analysis. Five primer combinations were used to detect 159 bands, of which 94 (59.1%) were polymorphic. A neighbour-joining tree based on the AFLP data showed no clear association between genotype and geographical origin. Furthermore, the AFLP data suggest that D. flagrans is mainly clonal and no recombination could be detected, not even within the same country. The low genetic variation in D. flagrans suggests that this fungus has recently diverged from a single progenitor. Based on estimations of mutation rates, it was calculated that this most recent common ancestor lived about 16000-23000 years ago.
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| 5. |
- Apoga, D, et al.
(författare)
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Adhesion of conidia and germlings of the plant pathogenic fungus Bipolaris sorokiniana to solid surfaces
- 2001
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Ingår i: Mycological Research. - 0953-7562. ; 105:10, s. 1251-1260
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Tidskriftsartikel (refereegranskat)abstract
- Soon after coming in contact with its host, the plant pathogenic fungus Bipolaris sorokiniana produces an extracellular material that appears to be important for adhering conidia and germlings to the host surface. To further understand this step of the infection, the adhesion of B. sorokiniana to artificial solid surfaces was examined. On a hydrophobic (polystyrene) surface adhesion occurred in two stages, the first by conidia and the second by germlings. Conidial adhesion occurred shortly (0-1 h) after hydration. The conidia were easily detached by increasing the shear force and including detergents in the washing buffer. As conidia were hydrophobic, these observations indicate that conidial adhesion to polystyrene is due to weak, hydrophobic interaction. The second stage of adhesion was accompanied by conidial germination and occurred 1-2 h after hydration and contact with the surface. Concomitant with the delayed adhesion, the fungus produced an extracellular matrix (ECM). The adhesion of germlings was firm and surface-unspecific since they adhered to both hydrophobic and hydrophilic (glass) surfaces, Except for strong bases, hydrochloric acid and broad-specificity proteases (including Pronase E), none of the hydrolytic enzymes, electrolyte solutions, ionic and hydrophobic detergents and organic solvents removed germlings from the solid surfaces. The adhesion of germlings incubated in the presence of the protein glycosylation inhibitor tunicamycin or the lectins Con A (Concanavalin A) and GNA (from Galanthus nivalis) was significantly reduced, which indicates the involvement of surface glycoproteins in this process. The surface proteins of germlings were labelled with I-125, extracted and analysed by two-dimensional gel electrophoresis. This revealed about 40 surface proteins over a wide pH range (4-10) with molecular masses between 10 and 100 kDa.
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| 6. |
- Apoga, D, et al.
(författare)
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Visualization and characterization of the extracellular matrix of Bipolaris sorokiniana
- 2000
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Ingår i: Mycological Research. - 0953-7562. ; 104:5, s. 564-575
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular matrix (ECM) surrounding conidia and germlings of B. sorokiniana was studied using light microscopy (LM), scanning (SEM) and transmission electron microscopy (TEM). Conidial ECM surrounding dry-inoculated, ungerminated conidia was fluid-like and observed only using a cryo-preparation technique, suggesting that the material was water soluble. ECM enveloping germlings appeared fibrillar in LM, TEM and SEM but amorphous in cryo-SEM, indicating that the structure of the ECM is dependent on the water content of the matrix. Fibrillar ECM formed thread-like structures that extended over long distances on the substrate or towards neighbouring conidia and hyphae. TEM of germlings negatively stained with uranyl acetate revealed the presence of fungal fimbriae. The strong resemblance between the extending organization of fibrillar thread-like ECM structures and fimbriae suggested that fimbriae constitute a basic structural component of the ECM and serve as the aggregation centre for the other ECM components. Histochemical labelling revealed significant differences between ECM surrounding the fungus at different morphological stages. The germ tube ECM was labelled for both proteins and polysaccharides whereas germling ECM consisted of two layers: an inner rich in proteins and an outer composed mainly of polysaccharides. Furthermore, the newly released ECM localized on germ tubes and hyphal tips showed affinity for microspheres carrying any type of surface properties while hyphal ECM had affinity only for negatively charged microspheres. This together suggests that ECM after its release is subjected to structural changes.
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| 7. |
- Articus, Kristina, et al.
(författare)
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Ribosomal DNA and beta-tubulin data do not support the separation of the lichens Usnea florida and U-subfloridana as distinct species
- 2002
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Ingår i: Mycological Research. - 0953-7562 .- 1469-8102. ; 106, s. 412-418
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Tidskriftsartikel (refereegranskat)abstract
- The lichens Usnea florida and U. subfloridana have since long been recognised as distinct species. They show many similarities in morphology, but have different reproductive strategies. Usnea florida is always provided with many apothecia and produces no specialised asexual propagules. Usnea subfloridana has soralia, isidiomorphs and occasionally apothecia. Phylogenetic analyses based on continuous sequences of the ITS and LSU regions of the nuclear ribosomal DNA and the gene coding for beta-tubulin, show that specimens of the two species form one monophyletic group of intermixed specimens, and not two groups corresponding to morphology, which Would have been expected if two species were at hand. The 'species pair' concept in lichenology is discussed. Other Usnea species included in the study are: U. articulata, U. barbata, U. ceratina, U. filipendula. U. hirta, U. rigida and U. wasmuthii.
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| 8. |
- Attitalla, Idress Hamad, et al.
(författare)
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A rapid molecular method for differentiating two special forms (lycopersici and radicis-lycopersici) of Fusarium oxysporum
- 2004
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Ingår i: Mycological Research. - 0953-7562 .- 1469-8102. ; 108:7, s. 787-794
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Tidskriftsartikel (refereegranskat)abstract
- Two pathogenic special forms (f. sp.) of the Fusarium oxysporum species complex f. sp. lycopersici (Fol) and f. sp. radicis-lycopersici (Forl) are morphologically indistinguishable. Although they are pathogenic to the same host genus Lycopersicon (tomato), and infect the same tomato cultivar, they form distinct diseases; Fol causes wilt and Forl causes crown rot and root rot. These two special forms apparently exist as genetically isolated populations, based on vegetative compatibility and molecular variation at the DNA level. In seeking efficient diagnostic tools for differentiating Fol and Forl isolates, we examined three techniques: isozyme analysis, mitochondrial DNA (mtDNA) RFLP by HaeIII-digestion of total genomic DNA, and an osmotic method using high performance liquid chromatography (HPLC) to detect fungal pigments. The isolates were collected from geographically widespread locations. Distinct HPLC-profile differences were found between an endophytic non-pathogenic isolate and the other pathogenic isolates. However, the direct mtDNA RFLP technique proved to be an efficient diagnostic tool for routine differentiation of Fol and Forl isolates.
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| 9. |
- Blaudez, D., et al.
(författare)
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Differential responses of ectomycorrhizal fungi to heavy metals in vitro
- 2000
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Ingår i: Mycological Research. - : Elsevier. - 0953-7562 .- 1469-8102. ; 104:11, s. 1366-1371
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Tidskriftsartikel (refereegranskat)abstract
- Thirty-nine ectomycorrhizal isolates of Paxillus involutus, Pisolithus tinctorius, Suillus bovinus, S. luteus and S. variegatus were tested on cadmium, copper, nickel and zinc amended media to determine their in vitro tolerance, measured as inhibition of biomass production. Twenty-one isolates were from heavy metal polluted sites, whereas the others were from non-contaminated soils. There was a strong interspecific variation in metal tolerance. S. luteus, S. variegatus and P. tinctorius were more tolerant of Cu, Cd and Zn when compared with P. involutus, whereas the reverse was true for Ni. A high intraspecific heterogeneity in metal tolerance was also found. EC50 values for isolates originating from polluted sites were not statistically different from EC50 values for isolates originating from non-contaminated sites. The findings are discussed in relation to the potential benefits of ectomycorrhizal fungi in protecting their host plants from metal contamination.
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| 10. |
- Chalot, Michel, et al.
(författare)
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Factors affecting amino-acid-uptake by the ectomycorrhizal fungus Paxillus involutus
- 1995
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Ingår i: Mycological Research. - 0953-7562. ; 99:9, s. 1131-1138
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Tidskriftsartikel (refereegranskat)abstract
- Factors affecting amino acid uptake by the ectomycorrhizal fungus Paxillus involutus were investigated using tracer kinetic experiments. Amino acid uptake by P. involutus was dependent on the pH of the incubation medium. Uptake of L-glutamate and L-glutamine had a distinct pH optimum around pH 4.0 and declined sharply between pH 4.5 and 6.4. Uptake of alanine and aspartate was also highest at low pH values (3-4) but declined more slowly with increasing pH. Total uptake of labelled amino acids was unaffected by 0.05 or 0.5 mM ammonium while 5 mM ammonium decreased amino acid uptake. Nitrate or glucose did not significantly affect amino acid uptake but glucose greatly increased the proportion of carbon that was respired. Uptake of the different amino acids decreased by a factor of 4 to 10 with increasing age (1-5 wk) and the proportion of absorbed C-14 that was respired increased with age. Changes in the size of the total amino acid pool were inversely related to those in the rate of uptake and the pool increased steadily with age. The implications of the ability of P. involutus to take up amino acids are discussed.
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