| 1. |
- Rosén, Stefan, et al.
(author)
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A multispecific saline-soluble lectin from the parasitic fungus Arthrobotrys oligospora. Similarities in the binding specificities compared with a lectin from the mushroom agaricus bisporus.
- 1996
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In: European journal of biochemistry / FEBS. - : Wiley. - 0014-2956 .- 1432-1033. ; 238:3, s. 830-7
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Journal article (peer-reviewed)abstract
- Several fungi can express high levels of saline-soluble and low-molecular-mass lectins that bind to glycoproteins such as fetuin and different mucins but not bind to any monosaccharides. In this paper, we report the binding specificities of such a lectin (designated AOL) isolated from the nematophagous fungus Arthrobotrys oligospora. The results show that AOL is a multispecific lectin that interacts with the following ligands: (a) Several sulfated glycoconjugates including sulfatide, dextran sulfate, and fucoidan. The specificity of this binding was indicated by experiments showing that none of the tested neutral- and sialic-acid-containing glycolipids, chondroitin sulfates B and C, heparin, and polyvinyl sulfate bound to AOL; (b) Phosphatidic acid and phospatidylglycerol, two out of several tested phospholipids. (c) N-linked and O-linked sugar chains bound to intact fetuin. The involvement of such sugar structures was demonstrated by analyzing the binding of AOL to chemically deglycosylated (trifluoromethanesulfonic acid) fetuin. Treating fetuin with O-glycosidase and N-glycosidase indicated that AOL bound to Gal beta GaLNAc alpha-Ser/Thr and to some N-linked complex sugars, respectively. Further assays demonstrated that AOL could interact with several other glycoproteins containing O-linked and/or N-linked sugar chains. The observations that AOL did not bind to free N-linked sugars isolated from fetuin, or to fetuin treated with trypsin or pronase, or to any of the tested neoglycoproteins and glycolipids with neutral- or sialic acid-containing sugars, indicated that the sugar chains need to be bound to an intact peptide backbone to interact with AOL. We have recently shown that the deduced primary structure of AOL has a high similarity to the sequence of a saline-soluble lectin isolated from the mushroom Agaricus bisporus (ABL) (Rosén, S., Kata, M., Persson, Y., Lipniunas, P. H., Wikström, M., van den Hondel, C. A. M. J. J., van den Brink, J. M., Rask, L., Hedén L.-O. and Tunlid, A., see companion paper). It is well known that ABL binds to Gal beta 3GaLNAc alpha-Ser/Thr, and in this paper we demonstrate that ABL binds to sulfatide, phosphatidic acid, phospatidylglycerol, and possibly also to the same N-linked complex sugars as AOL. The above data indicate that AOL and ABL are members of a novel family of fungal lectins sharing similar primary structure and binding properties.
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| 2. |
- Valeur, Anders, et al.
(author)
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Differences in lipid composition between free-living and initially adhered cells of a Gram-negative bacterium
- 1988
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In: Archives of Microbiology. - 0302-8933. ; 149:6, s. 521-526
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Journal article (peer-reviewed)abstract
- The phospholipid fatty acid composition and poly-β-hydroxybutyrate (PHB) content of initially adhered and free-living cells of a Pseudomonas sp. isolated from the rape plant Brassica napus were examined with gas chromatography (GC). Five different adhesion experiments were made including variations in surface charge (hydrophilic and lipophilic), temperature, media composition and time of adhesion. Lipids and poly-β-hydroxybutyrate (PHB) were extracted with a chloroform-methanol-water mixture, hydrolyzed and esterified with pentafluorobenzyl bromide. Analysis was performed with capillary gas chromatography and flame ionization detection. A pronounced difference in both the ratio saturated/unsaturated fatty acids and in PHB content between free-living and adhered bacteria were found. The free-living bacteria has a significantly smaller ratio of saturated/unsaturated C16 and C18 fatty acids and also a smaller ratio of total C18/total C16 fatty acids. Bacteria adhered to the lipophilic surface had a higher ratio of saturated to unsaturated C16 fatty acids than at the hydrophilic surface. There were no major differences between the treatments regarding the amount of bacteria adhered to the surface or their lipid composition.
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| 3. |
- Ahrén, Dag, et al.
(author)
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Comparison of gene expression in trap cells and vegetative hyphae of the nematophagous fungus Monacrosporium haptotylum
- 2005
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In: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 151:3, s. 789-803
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Journal article (peer-reviewed)abstract
- Nematode-trapping fungi enter the parasitic stage by developing specific morphological structures called traps. The global patterns of gene expression in traps and mycelium of the fungus Monacrosporium haptotylum were compared. The trap of this fungus is a unicellular spherical structure called the knob, which develops on the apex of a hyphal branch. RNA was isolated from knobs and mycelium and hybridized to a cDNA array containing probes of 2822 EST clones of M. haptotylum. Despite the fact that the knobs and mycelium were grown in the same medium, there were substantial differences in the patterns of genes expressed in the two cell types. In total, 23(.)3% (657 of 2822) of the putative genes were differentially expressed in knobs versus mycelium. Several of these genes displayed sequence similarities to genes known to be involved in regulating morphogenesis and cell polarity in fungi. Among them were several putative homologues for small GTPases, such as rho1, rac1 and ras1, and a rho GDP dissociation inhibitor (rdi1). Several homologues to genes involved in stress response, protein synthesis and protein degradation, transcription, and carbon metabolism were also differentially expressed. In the last category, a glycogen phosphorylase (gph1) gene homologue, one of the most upregulated genes in the knobs as compared to mycelium, was characterized. A number of the genes that were clifferentially expressed in trap cells are also known to be regulated during the development of infection structures in plant-pathogenic fungi. Among them, a gas1 (mas3) gene homologue (designated gks1), which is specifically expressed in appressoria of the rice blast fungus, was characterized.
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| 4. |
- Ahrén, Dag, et al.
(author)
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Evolution of parasitism in nematode-trapping fungi
- 2003
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In: Journal of Nematology. - 0022-300X. ; 35:2, s. 194-197
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Conference paper (peer-reviewed)abstract
- We are studying the evolution of parasitism in a group of soil-living ascomycetes that can grow as saprophytes as well as parasites by forming special morphological structures called traps. Analyses of 18S ribosomal DNA sequences have shown that these fungi form a monophyletic and isolated clade among the ascomycetes. The phylogenetic patterns within this clade are concordant with the morphology of the traps and separate species having adhesive traps (nets, knobs, and branches) from those having constricting rings. This suggests that these nematode-trapping fungi have a common ancestor, and that the ability to capture nematodes has been an important trait for further speciation and diversification within the clade. To obtain information on the genomic basis for this pattern, we recently started a large-scale sequencing project of the nematode-trapping fungus Monacrosporium haptotylum. This will allow the identification of genes uniquely expressed during the development of traps, and elucidate the molecular evolution Of Such genes within the nematode-trapping fungi clade.
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| 5. |
- Ahrén, Dag, et al.
(author)
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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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In: Mycological Research. - 0953-7562. ; 108, s. 1205-1214
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Journal article (peer-reviewed)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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| 6. |
- Ahrén, Dag, et al.
(author)
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PHOREST: a web-based tool for comparative analyses of expressed sequence tag data
- 2004
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In: Molecular Ecology Notes. - : Wiley. - 1471-8278 .- 1471-8286. ; 4:2, s. 311-314
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Journal article (peer-reviewed)abstract
- Comparative analysis of expressed sequence tags is becoming an important tool in molecular ecology for comparing gene expression in organisms grown in certain environments. Additionally, expressed sequence tag database information can be used for the construction of DNA microarrays and for the detection of single nucleotide polymorphisms. For such applications, we present PHOREST, a web-based tool for managing, analysing and comparing various collections of expressed sequence tags. It is written in PHP (PHP: Hypertext Preprocessor) and runs on UNIX, Microsoft Windows and Macintosh (Mac OS X) platforms.
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| 7. |
- Ahrén, Dag, et al.
(author)
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Phylogeny of nematode-trapping fungi based on 18S rDNA sequences
- 1998
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In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 158:2, s. 179-184
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Journal article (peer-reviewed)abstract
- The small subunit (SSU) ribosomal DNA (18S rDNA) from 15 species of nematode-trapping fungi and closely related non-parasitic species were sequenced. Phylogenetic analysis indicated that species within the genera of Arthrobotrys, Dactylaria, Dactylella, Monacrosporium and Duddingtonia formed a monophyletic and isolated clade among an unresolved cluster of apothecial ascomycetes. The phylogenetic patterns within this clade were not concordant with the morphology of the conidia nor the conidiophores, but rather with that of the infection structures. The results from the different methods of tree reconstruction supported three lineages; the species having constricting rings, the non-parasitic species and the species having various adhesive structures (nets, hyphae, knobs and non-constricting rings) to infect nematodes.
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| 8. |
- Andersson, Erika, et al.
(author)
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A contrast variation SANS and SAXS study of soil derived dissolved organic matter, and its interactions with hematite nanoparticles
- 2023
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In: JCIS Open. ; 11
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Journal article (peer-reviewed)abstract
- Soil derived dissolved organic matter (DOM) is an important component of the carbon cycle and influences numerous biogeochemical processes, including the formation of mineral-organic associations. DOM ranges in size from small organic molecules to macromolecules and colloidal aggregates. In this study we have used small angle neutron (SANS) and X-ray (SAXS) scattering to characterize the colloidal DOM fraction from the organic layer of a boreal forest soil, and its interactions with hematite (α-Fe2O3) mineral nanoparticles. Comparison between SAXS and contrast variation SANS patterns revealed that the scattering form factor of the colloidal DOM aggregates was essentially independent of the scattering contrast, implying that the colloidal aggregates have an essentially homogeneous chemical composition, down to the nanometre length scale. Variation of the D2O/H2O ratio of the solvent yielded a SANS intensity minimum at ca. 40 vol % D2O, which was consistent with colloids composed of mainly polysaccharides. At pH 5.5 the pure hematite nanoparticles were colloidally stable in water and characterized by a ζ-potential of +25 mV and a hydrodynamic radius of ca. 70 nm. In the presence of DOM, the hematite nanoparticles lost the colloidal stability and aggregated into larger clusters, displaying a negative ζ-potential of ca. −25 mV. The charge reversal suggested that negatively charged polyanions of DOM adsorbed onto the hematite particles, possibly leading to bridging flocculation. Our results suggested that mainly low molecular weight components induced hematite aggregation because no or very limited interactions between DOM colloids and hematite were detected.
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| 9. |
- Andersson, Erika, et al.
(author)
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Generation and properties of organic colloids extracted by water from the organic horizon of a boreal forest soil
- 2023
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In: Geoderma. - : Elsevier BV. - 0016-7061. ; 432
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Journal article (peer-reviewed)abstract
- Organic colloids are an important part of dissolved organic matter (DOM) yet many of their properties remain elusive. The main aims of this study were to assess how the colloidal properties of DOM extracted with water from an organic boreal soil horizon varied with the extraction protocol, and thereby provide insight into the nature of the DOM colloids and develop a mechanistic understanding of how the colloids were generated from the parent soil aggregates. This was accomplished by systematic variations of extraction temperature (4 °C–100 °C), time, mechanical agitation, and pH, together with a combination of chemical analyses, and light and X-ray scattering. Our results agreed with the previous identification of two main colloidal DOM species, one fractal cluster and a second, smaller colloidal DOM species described as chains or coils. Fractal clusters completely dominated the colloidal DOM in extracts from our soil at room temperature and below. Colloidal coils only existed in DOM extracted above room temperature, and their amount increased significantly between 50 °C–100 °C. Moreover, the temperature variation indicated that the fractal clusters partly dissolved into colloidal coils at elevated temperatures. Mechanical agitation at 4 °C significantly increased the amount of DOM extracted, increasing the concentrations of both fractal clusters and low-molecular weight organic compounds. While the clusters were extracted from agitated and non-agitated soil suspensions, the low molecular weight organics were mainly released by agitation. Based on the experimental observations, we propose a conceptual model where parent soil aggregates contain the fractal clusters in mobile and occluded forms, and that the occluded clusters co-exist with occluded low molecular weight organics. These occluded forms may be released by mechanical forces, increasing pH and temperature. At higher temperatures, the soil aggregates and the fractal clusters start to break up, and subsequently individual colloidal coils, presumably carbohydrates, disperse in the water phase. The model explains the origin and properties of the fractal clusters that completely dominate the colloidal DOM extracted from our soil at room temperature and below.
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| 10. |
- Andersson, Karl-Magnus, et al.
(author)
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Interspecific and host-related gene expression patterns in nematode-trapping fungi.
- 2014
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In: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 15:1
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Journal article (peer-reviewed)abstract
- Nematode-trapping fungi are soil-living fungi that capture and kill nematodes using special hyphal structures called traps. They display a large diversity of trapping mechanisms and differ in their host preferences. To provide insights into the genetic basis for this variation, we compared the transcriptome expressed by three species of nematode-trapping fungi (Arthrobotrys oligospora, Monacrosporium cionopagum and Arthrobotrys dactyloides, which use adhesive nets, adhesive branches or constricting rings, respectively, to trap nematodes) during infection of two different plant-pathogenic nematode hosts (the root knot nematode Meloidogyne hapla and the sugar beet cyst nematode Heterodera schachtii).
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