| 1. |
- Balouet, Jean Christophe, et al.
(författare)
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Dendrochemistry of Multiple Releases of Chlorinated Solvents at a Former Industrial Site
- 2012
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:17, s. 9541-9547
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Tidskriftsartikel (refereegranskat)abstract
- Trees can take up and assimilate contaminants from the soil, subsurface, and groundwater. Contaminants in the transpiration stream can become bound or incorporated into the annual rings formed in trees of the temperate zones. The chemical analysis of precisely dated tree rings, called dendrochemistry, can be used to interpret past plant interactions with contaminants. This investigation demonstrates that dendrochemistry can be used to generate historical scenarios of past contamination of groundwater by chlorinated solvents at a site in Verl, Germany. Increment cores from trees at the Verl site were collected and analyzed by energy-dispersive X-ray fluorescence (EDXRF) line scanning. The EDXRF profiles showed four to six time periods where tree rings had anomalously high concentrations of chlorine (Cl) as an indicator of potential contamination by chlorinated solvents.
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| 2. |
- Brun, Annick, et al.
(författare)
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Structure and function of the ectomycorrhizal association between Paxillus involutus (Batsch) Fr. and Betula pendula Roth .L. Dynamics of mycorrhiza formation
- 1995
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Ingår i: New Phytologist. - 1469-8137. ; 129:3, s. 487-493
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Tidskriftsartikel (refereegranskat)abstract
- Detailed examination of the structural and functional integration taking place during mycorrhiza formation necessitates rapid and aseptic synthesis of uniform mycorrhizal structures at well-defined stages of development. A system is described for formation of ectomycorrhizas between Betula pendula Roth. and Paxillus involutus (Batsch) Fr. Small sterile seedlings were placed directly on fungal colonies growing on cellophane covered agar plates. Microscopic examination during the course of development indicated an initial rapid colonization of the roots and formation of a fully developed mantle within 2-4 d. Hartig net formation was evident after 8 d of contact and involved a transition from a paraepidermal organization to a mature periepidermal Hartig net after 15 d of contact. Using a standard fungal growth medium, formation and development of mycorrhizas were not greatly affected by changes in the overall concentrations of nitrogen and phosphorus but changes in the ratio of nitrogen to phosphorus had strong effects on development and mycorrhiza formation was completely suppressed when the ratio of nitrogen to phosphorus was increased. These differences were not related to the effects of nitrogen or phosphorus on linear growth of the fungus.
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| 3. |
- 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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| 4. |
- Chalot, Michel, et al.
(författare)
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Kinetics, energetics and specificity of a general amino acid transporter from the ectomycorrhizal fungus Paxillus involutus
- 1996
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 142, s. 1749-1756
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics, energetics and specificity of a general amino acid transporter were studied in the ectomycorrhizal fungus Paxillus involutus (Batsch) Fr. The uptake of amino acids showed features characteristic of active transport. After correction for a non-mediated transport component, the kinetics of glutamate, glutamine, alanine and aspartate uptake measured over a wide concentration range followed the simple Michaelis-Menten saturation curves, The apparent K-m derived from the Eadie-Hofstee plots ranged from 7 mu M for alanine to 27 mu M for glutamate, Dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone and NaN3 strongly inhibited amino acid uptake, whereas dicyclohexylcarbodiimide. vanadate and the ionophores monensin and nonactin had no effect on the uptake. Both ph dependence and inhibition by protonophores are consistent with a proton symport mechanism for amino acid uptake by P. involutus, Competition studies indicated a broad substrate recognition by the uptake system, which resembles the general amino acid permease of yeast, Dixon plots of the inhibition of glutamate uptake by alanine, lysine and methionine sulfoximine showed that inhibitions were competitive, Tire physiological importance of this transporter for the exchange of nitrogenous compounds between fungal and host plant cells in ectomycorrhizal associations is discussed.
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| 5. |
- Chalot, Michel, et al.
(författare)
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Metabolism of [N-15]alanine in the ectomycorrhizal fungus Paxillus involutus
- 1995
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Ingår i: Experimental Mycology. - : Elsevier BV. - 0147-5975. ; 19:4, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- Alanine metabolism in the ectomycorrhizal fungus Paxillus involutus was investigated using [N-15]alanine. Short-term exposure of mycelial discs to [N-15]alanine showed that the greatest flow of N-15 was to glutamate and to aspartate. Levels of enrichment were as high as 15-20% for glutamate and 13-18% for aspartate, whereas that of alanine reached 30%. Label was also detected in the amino-N of glutamine and in serine and glycine, although at lower levels. Preincubation of mycelia with aminooxyacetate, an inhibitor of transamination reactions, resulted in complete inhibition of the flow of the label to glutamate, aspartate, and amino-N of glutamine, whereas [N-15]alanine rapidly accumulated. This evidence indicates the direct involvement of alanine aminotransferase for translocation of N-15 from alanine to glutamate. Alanine may be a convenient reservoir of both nitrogen and carbon. (C) 1995 Academic Press, Inc.
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| 6. |
- Chalot, Michel, et al.
(författare)
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Respiration of [C-14] alanine by the ectomycorrhizal fungus Paxillus involutus
- 1994
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968 .- 0378-1097. ; 121:1, s. 87-91
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Tidskriftsartikel (refereegranskat)abstract
- The ectomycorrhizal fungus Paxillus involutus efficiently took up exogenously supplied [C-14]alanine and rapidly converted it to pyruvate, citrate, succinate, fumarate and to CO2, thus providing direct evidence for the utilisation of alanine as a respiratory substrate. [C-14]alanine was further actively metabolised to glutamate, glutamine and aspartate. Exposure to aminooxyacetate completely suppressed (CO2)-C-14 evolution and greatly reduced the flow of carbon from [C-14]alanine to tricarboxylic acid cycle intermediates and amino acids, suggesting that alanine aminotransferase plays a pivotal role in alanine metabolism in Paxillus involutus.
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| 7. |
- Javelle, Arnaud, et al.
(författare)
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Ammonium and methylamine transport by the ectomycorrhizal fungus Paxillus involutus and ectomycorrhizas
- 1999
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 30:4, s. 355-366
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Tidskriftsartikel (refereegranskat)abstract
- Using [C-14]methylamine as an analogue of ammonium, the kinetics and the energetics of NH: transport were studied in the ectomycorrhizal fungus, Paxillus involutus (Batsch) Fr. The apparent half-saturation constant (K-m) and the maximum uptake rate (V-max) for the carrier-mediated transport derived from the Eadie-Hofstee transformation were 180 mu M and 380 nmol (mg dry wt)(-1) min(-1,) respectively. Both pH dependence and inhibition by protonophores indicate that methylamine transport in P. involutus was dependent on the electrochemical H+ gradient. Both long-term and short-term uptake experiments were consistent with regulation of ammonium/methylamine transport processes by the presence of an organic nitrogen source. Analysis of methylamine uptake by different P. involutus isolates revealed no obvious trend in the uptake capacities in relation to N deposition at the collection site. Kinetic parameters were determined in P. involutus/Betula pendula (Roth.) axenic association and in detached mycorrhizal roots isolated from forest sites. Enhanced methylamine uptake in the presence of the fungal symbiont was demonstrated. Homogeneous V-max values were found for axenic and detached mycorrhizas, whereas K-m values showed greater variations. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
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| 8. |
- Morel, M, et al.
(författare)
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Identification of genes differentially expressed in extraradical mycelium and ectomycorrhizal roots during Paxillus involutus-Betula pendula ectomycorrhizal symbiosis
- 2005
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 71:1, s. 382-391
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Tidskriftsartikel (refereegranskat)abstract
- The development of ectomycorrhizal symbiosis leads to drastic changes in gene expression in both partners. However, little is known about the spatial regulation of symbiosis-regulated genes. Using cDNA array profiling, we compared the levels of expression of fungal genes corresponding to approximately 1,200 expressed sequenced tags in the ectomycorrhizal root tips (ECM) and the connected extraradical mycelium (EM) for the Paxillus involutus-Betuld pendula ectomycorrhizal association grown on peat in a microcosm system. Sixty-five unique genes were found to be differentially expressed in these two fungal compartments. In ECM, a gene coding for a putative phosphatidylserine decarboxylase (Psd) was up-regulated by 24-fold, while genes coding for urea (Dur3) and spermine (Tpo3) transporters were up-regulated 4.1- and 6.2-fold in EM. Moreover, urea was the major nitrogen compound found in EM by gas chromatography-mass spectrometry analysis. These results suggest that (i) there is a spatial difference in the patterns of fungal gene expression between ECM and EM, (ii) urea and polyamine transporters could facilitate the translocation of nitrogen compounds within the EM network, and (iii) fungal Psd may contribute to membrane remodeling during ectomycorrhiza formation.
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| 9. |
- Olsson, Pål Axel, et al.
(författare)
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Ectomycorrhizal mycelia reduce bacterial activity in a sandy soil
- 1996
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 21:2, s. 77-86
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial activity was studied in a growth system containing Pinus contorta seedlings inoculated with different mycorrhizal fungi. Nylon nets enabled separation of soil compartments with extramatrical mycorrhizal hyphae from soil compartments with roots and mycelium. In three separate experiments bacterial activity, estimated as thymidine incorporation, was reduced in soils with Paxillus involutus hyphae compared to controls without mycorrhizal hyphae. This effect was found irrespective of compartments with and without roots were compared. Laccaria bicolor only reduced the activity in one of these three experiments. Thelephora terrestris (tested in two experiments), Laccaria proxima, Suillus variegatus and Hebeloma crustuliniforme (one experiment), also reduced the thymidine and leucine incorporation rates of bacteria. The reduction for these fungi varied between 20% and 50% in all experiments. Numbers of viable bacteria appeared to be reduced by T. terrestris, L. proxima, S. variegatus and H. crustuliniforme in one experiment, while no effect was seen in the other experiments.
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| 10. |
- Smith, Kevin T., et al.
(författare)
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Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)
- 2014
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 95, s. 58-62
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Tidskriftsartikel (refereegranskat)abstract
- Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intraannual p'rocesses, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations.
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