| 1. |
- Hammer, Edith, et al.
(författare)
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A mycorrhizal fungus grows on biochar and captures phosphorus from its surfaces
- 2014
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 77, s. 252-260
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Tidskriftsartikel (refereegranskat)abstract
- Biochar application to soils has potential to simultaneously improve soil fertility and store carbon to aid climate change mitigation. While many studies have shown positive effects on plant yields, much less is known about the synergies between biochar and plant growth promoting microbes, such as mycorrhizal fungi. We present the first evidence that arbuscular mycorrhizal (AM) fungi can use biochar as a physical growth matrix and nutrient source. We used monoxenic cultures of the AM fungus Rhizophagus irregularis in symbiosis with carrot roots. Using scanning electron microscopy we observed that AM fungal hyphae grow on and into two contrasting types of biochar particles, strongly attaching to inner and outer surfaces. Loading a nutrient-poor biochar surface with nutrients stimulated hyphal colonization. We labeled biochar surfaces with P-33 radiotracer and found that hyphal contact to the biochar surfaces permitted uptake of P-33 and its subsequent translocation to the associated host roots. Direct access of fungal hyphae to biochar surfaces resulted in six times more P-33 translocation to the host roots than in systems where a mesh prevented hyphal contact with the biochar. We conclude that AM fungal hyphae access microsites within biochar, that are too small for most plant roots to enter (<10 mu m), and can hence mediate plant phosphorus uptake from the biochar. Thus, combined management of biochar and AM fungi could contribute to sustainable soil and climate management by providing both a carbon-stable nutrient reservoir and a symbiont that facilitates nutrient uptake from it. (C) 2014 Elsevier Ltd. All rights reserved.
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| 2. |
- Hammer, Edith, et al.
(författare)
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Elemental composition of arbuscular mycorrhizal fungi at high salinity.
- 2011
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 21, s. 117-129
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the elemental composition of spores and hyphae of arbuscular mycorrhizal fungi (AMF) collected from two saline sites at the desert border in Tunisia, and of Glomus intraradices grown in vitro with or without addition of NaCl to the medium, by proton-induced X-ray emission. We compared the elemental composition of the field AMF to those of the soil and the associated plants. The spores and hyphae from the saline soils showed strongly elevated levels of Ca, Cl, Mg, Fe, Si, and K compared to their growth environment. In contrast, the spores of both the field-derived AMF and the in vitro grown G. intraradices contained lower or not elevated Na levels compared to their growth environment. This resulted in higher K:Na and Ca:Na ratios in spores than in soil, but lower than in the associated plants for the field AMF. The K:Na and Ca:Na ratios of G. intraradices grown in monoxenic cultures were also in the same range as those of the field AMF and did not change even when those ratios in the growth medium were lowered several orders of magnitude by adding NaCl. These results indicate that AMF can selectively take up elements such as K and Ca, which act as osmotic equivalents while they avoid uptake of toxic Na. This could make them important in the alleviation of salinity stress in their plant hosts.
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| 3. |
- Hammer, Edith, et al.
(författare)
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Tit for tat? A mycorrhizal fungus accumulates phosphorus under low plant carbon availability.
- 2011
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 76, s. 236-244
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Tidskriftsartikel (refereegranskat)abstract
- The exchange of carbohydrates and mineral nutrients in the arbuscular mycorrhizal symbiosis must be controlled by both partners in order to sustain an evolutionarily stable mutualism. Plants down-regulate their carbon flow to the fungus when nutrient levels are sufficient, while the mechanism controlling fungal nutrient transfer is unknown. Here we show that the fungus accumulates nutrients when connected to a host that is of less benefit to the fungus, indicating a potential of the fungus to control the transfer of nutrients. We used a monoxenic in vitro model of root organ cultures associated with G. intraradices, in which we manipulated the carbon availability to the plant. We found that G. intraradices accumulated up to 7 times more nutrients in its spores, and up to 9 times more in its hyphae, when the carbon pool available to the associated roots was halved. The strongest effect was found for phosphorus, considered to be the most important nutrient in the arbuscular mycorrhizal symbiosis. Other elements such as potassium and chorine were also accumulated, but to a lesser extent, while no accumulation of iron or manganese was found. Our results suggest a functional linkage between carbon and phosphorus exchange.
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| 4. |
- Lekberg, Ylva, et al.
(författare)
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Fatty acid 16:1ω5 as a proxy for arbuscular mycorrhizal fungal biomass : current challenges and ways forward
- 2022
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Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 58:8, s. 835-842
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Tidskriftsartikel (refereegranskat)abstract
- Fatty acid biomarkers have emerged as a useful tool to quantify biomass of various microbial groups. Here we focus on the frequent use of the fatty acid 16:1ω5 as a biomarker for arbuscular mycorrhizal (AM) fungi in soils. We highlight some issues with current applications of this method and use several examples from the literature to show that the phospholipid fatty acid (PLFA) 16:1ω5 can occur in high concentrations in soils where actively growing AM fungi are absent. Unless the study includes a control where the contribution of other microbes can be estimated, we advocate for the use of the neutral lipid fatty acid (NLFA) 16:1ω5. This biomarker has higher specificity, is more responsive to shifts in AM fungal biomass, and quantification can be conducted along with PLFA analysis without doubling analytical efforts. We conclude by contrasting various methods used to measure AM fungal biomass in soil and highlight future research needs to optimize fatty acid analyses.
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| 5. |
- Lekberg, Ylva, et al.
(författare)
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Plants as resource islands and storage units - adopting the mycocentric view of arbuscular mycorrhizal networks
- 2010
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 74:2, s. 336-345
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Tidskriftsartikel (refereegranskat)abstract
- The majority of herbaceous plants are connected by arbuscular mycorrhizal (AM) fungi in complex networks, but how this affects carbon (C) and phosphorus (P) allocation among symbionts is poorly understood. We utilized a monoxenic AM system where hyphae from donor roots colonized two younger receiver roots of varying C status. AM fungal C allocation from donor to receiver compartments was followed by measuring the 13C contents in fungal- and plant-specific lipids, and P movement from a hyphal compartment was traced using 33P. Four times more 13C was translocated from donor to C-limited receiver roots, but C remained in fungal tissue. Root C status did not influence the overall AM colonization, but arbuscule density was twice as high in non-C-limited roots, and they received 10 times more 33P. The number of hyphal connections between compartments did not influence C and P allocation. Interestingly, there were more fungal storage lipids, but fewer structural lipids inside C-limited roots. Our results indicate that AM colonization may poorly reflect host quality as C can be supplied from neighboring roots. A mycocentric view of the symbiosis is proposed where C-delivering hosts are resource islands for the exchange of P for C, and C-limited hosts are storage units.
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| 6. |
- Olsson, Ola, et al.
(författare)
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Phosphorus and carbon availability regulate structural composition and complexity of AM fungal mycelium.
- 2014
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 24:6, s. 443-451
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Tidskriftsartikel (refereegranskat)abstract
- The regulation of the structural composition and complexity of the mycelium of arbuscular mycorrhizal (AM) fungi is not well understood due to their obligate biotrophic nature. The aim of this study was to investigate the structure of extraradical mycelium at high and low availability of carbon (C) to the roots and phosphorus (P) to the fungus. We used monoxenic cultures of the AM fungus Rhizophagus irregularis (formerly Glomus intraradices) with transformed carrot roots as the host in a cultivation system including a root-free compartment into which the extraradical mycelium could grow. We found that high C availability increased hyphal length and spore production and anastomosis formation within individual mycelia. High P availability increased the formation of branched absorbing structures and reduced spore production and the overall length of runner hyphae. The complexity of the mycelium, as indicated by its fractal dimensions, increased with both high C and P availability. The results indicate that low P availability induces a growth pattern that reflects foraging for both P and C. Low C availability to AM roots could still support the explorative development of the mycelium when P availability was low. These findings help us to better understand the development of AM fungi in ecosystems with high P input and/or when plants are subjected to shading, grazing or any management practice that reduces the photosynthetic ability of the plant.
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| 7. |
- Olsson, Pål Axel, et al.
(författare)
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Elemental composition in vesicles of an arbuscular mycorrhizal fungus, as revealed by PIXE analysis.
- 2011
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Ingår i: Fungal Biology. - : Elsevier BV. - 1878-6146. ; 115:7, s. 643-648
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Tidskriftsartikel (refereegranskat)abstract
- We investigated element accumulation in vesicles of the arbuscular mycorrhizal (AM) fungus Glomus intraradices, extracted from the roots of inoculated leek plants. The elemental composition (elements heavier than Mg) was quantified using particle-induced X-ray emission (PIXE), in combination with scanning transmission ion microscopy (STIM). In vesicles, P was the most abundant of the elements analysed, followed by Ca, S, Si and K. We analysed 12 vesicles from two root systems and found that the variation between vesicles was particularly high for P and Si. The P content related positively to Si, Zn and K, while its relation to Cl fitted to a negative power function. Vesicle transects showed that P and K were present in central parts, while Ca was present mainly near the vesicle surfaces. The results showed that P is an important part (0.5% of the dry weight) of the vesicle content and that the distribution of some elements, within mycelia, may be strongly correlated.
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| 8. |
- Olsson, Pål Axel, et al.
(författare)
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Phosphorus Availability Influences Elemental Uptake in the Mycorrhizal Fungus Glomus intraradices, as Revealed by PIXE Analysis.
- 2008
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 74:13, s. 4144-4148
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Tidskriftsartikel (refereegranskat)abstract
- We investigated element accumulation in the arbuscular mycorrhizal fungus Glomus intraradices. Fungal spores and mycelium growing in monoxenic cultures were analyzed. The elemental composition was quantified using particle-induced X-ray emission (PIXE) in combination with scanning transmission ion microscopy. In the spores, Ca and Fe were mainly associated with the spore wall; while P and K showed patchy distributions and their concentrations were correlated. Excess of P in the hyphal growth medium increased the P and Si concentration in spores, and increased the K:Ca ratio in spores. Increased P availability decreased the concentration of Zn and Mn in spores. We conclude that the availability of P influences the uptake and accumulation of several elements in spores. It is demonstrated that PIXE analysis is a powerful tool for quantitative analysis of elemental accumulation in fungal mycelia.
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| 9. |
- Pallon, Jan, et al.
(författare)
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Symbiotic fungi that are essential for plant nutrient uptake investigated with NMP
- 2007
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 260:1, s. 149-152
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear microprobe (NMP) technique using PIXE for elemental analysis and STIM on/off axis for parallel mass density normalization has proven successful to investigate possible interactions between minerals and ectomycorrhizal (EM) mycelia that form symbiotic associations with forest trees. The ability for the EM to make elements biologically available from minerals and soil were compared in field studies and in laboratory experiments, and molecular analysis (PCR-RFLP) was used to identify ectomycorrhizal species from the field samplings. EM rhizomorphs associated with apatite in laboratory systems and in mesh bags incubated in forest ecosystems contained larger amounts of Ca than similar rhizomorphs connected to acid-washed sand. EM mycelium produced in mesh bags had a capacity to mobilize P from apatite-amended sand and a high concentration of K in some rhizomorphs suggests that these fungi are good accumulators of K and may have a significant role in transporting K to trees. Spores formed by arbuscular mycorrhizal (AM) fungi in laboratory cultures were compared with spores formed in saline soils in Tunisia in Northern Africa. We found lower concentrations of P and higher concentrations of Cl in the spores collected from the field than in the spores collected from laboratory cultures. For the case of laboratory cultures, the distribution of e.g. P and K was found to be clearly correlated.
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| 10. |
- Tømmerås, Karin, et al.
(författare)
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Immunolocalization of Cholecystokinin-2 Receptors in Rat Gastric Mucosa
- 2002
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 37:9, s. 1017-1024
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Gastrin exerts trophic effects on the gastric mucosa by mechanisms not yet completely elucidated. Our aim was to localize the cholecystokinin-2 (CCK2) receptor in epithelial cells of foetal and adult rat stomachs in order to determine the cell types that are directly affected by gastrin.METHODS: Gastric tissue was subjected to indirect double immunofluorescence staining with antiserum against the C-terminal decapeptide of the CCK2 receptor and antibodies against 5' bromo-2-deoxyuridine, which had been injected into the rats I h before they were killed, the acid pump H,K-ATPase, the membrane-cytoskeletal linker ezrin, pepsin/pepsinogen or histidine decarboxylase.RESULTS: Undifferentiated foetal gastric epithelial cells expressed CCK2 receptors, whereas stem cells of adult gastric glands did not exhibit immunoreactivity. However, other epithelial cells in the progenitor zone of adult gastric glands did express CCK2 receptors. Some of these cells were faintly stained for H,K-ATPase; pepsin/pepsinogen was also detected in this region. Parietal cells in the isthmus/pit region of the glands contained ezrin, and some showed weak immunoreactivity for the CCK2 receptor. As expected, enterochromaffin-like cells also expressed CCK2 receptors.CONCLUSION: Our findings are consistent with the hypothesis that a CCK2 receptor mediates direct effects of gastrin on gastric epithelial cells during both stomach organogenesis and adult life.
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