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Extraradical Mycelium (extraradical + mycelium)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Mycoparasitism of arbuscular mycorrhizal fungi: a pathway for the entry of saprotrophic fungi into roots

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2010
Nathalie De Jaeger
Abstract Within the rhizosphere, arbuscular mycorrhizal (AM) fungi interact with a cohort of microorganisms, among which is the biological control agent, Trichoderma spp. This fungus parasitizes a wide range of phytopathogenic fungi, a phenomenon also reported in the extraradical mycelium (ERM) of AM fungi. Here, we question whether the mycoparasitism of the ERM could be extended to the intraradical mycelium (IRM), thus representing a pathway for the entry of Trichoderma harzianum within the root. Microcosm experiments allowing interactions between Glomus sp. MUCL 41833 placed in a clade that contains the recently described species Glomus irregulare and T. harzianum were set up under in vitro autotrophic culture conditions using potato as a host. A microscope camera-imaging system, coupled with succinate dehydrogenase staining, was used to assess the mycoparasitism in the ERM and IRM. Trichoderma harzianum colonized the ERM of the AM fungus and spread into the IRM, before exiting into the root cells. Intrahyphal growth of T. harzianum caused protoplasm degradation, decreasing the ERM and IRM viability. ERM of the AM fungus represented a pathway for the entry of T. harzianum into the roots of potato. It further sets off the debate on the susceptibility of the AM fungi of being infected by microorganisms from the rhizosphere. [source]

Influence of arbuscular mycorrhizal mycelial exudates on soil bacterial growth and community structure

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2007
Jonas F. Toljander
Abstract Plant root systems colonized by arbuscular mycorrhizal (AM) fungi have previously been shown to influence soil bacterial populations; however, the direct influence of the AM extraradical mycelium itself on bacterial growth and community composition is not well understood. In this study, we investigated the effects of exudates produced by AM extraradical mycelia on the growth and development of an extracted soil bacterial community in vitro. The chemical composition of the mycelial exudates was analysed using proton nuclear magnetic resonance spectrometry. Following the addition of exudates to a bacterial community extracted from soil, bacterial growth and vitality were determined using a bacterial vitality stain and fluorescence microscopy. Changes in community composition were also analysed at various times over the course of 3 days by terminal restriction fragment length polymorphism analysis, in combination with cloning and sequencing of 16S rRNA genes. Mycelial exudates increased bacterial growth and vitality and changed bacterial community composition. Several Gammaproteobacteria, including a taxon within the Enterobacteriaceae, increased in frequency of occurrence in response to AM mycelial exudates. This study is the first attempt to identify carbohydrates from the extraradical mycelium of an AM fungus, and demonstrates the direct effects of mycelial exudates on a soil bacterial community. [source]

Allocation of plant carbon to foraging and storage in arbuscular mycorrhizal fungi

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2003
Mayra E Gavito
Abstract Foraging strategies, the cost,benefit associated with the search for new resources, have only begun to be explored in arbuscular mycorrhizal fungi (AMF). We show the use of 13C-labelling, via shoot photosynthesis, of the 16:1,5 fatty acid biomarker (the dominant and rather specific fatty acid in AMF storage lipids) to study the immediate patterns of carbon allocation to fungal lipids in response to inorganic and organic nutrient amendments. Signature fatty acid measurements, the incorporation of the label and complementary hyphal length density measurements showed that the extraradical mycelium of AMF proliferated in response to all the amendments provided whereas its development into unamended sand was minor in all treatments. We demonstrate the foraging capacity of AMF, linked to plant carbon, through their hyphal proliferation and accumulation of energy reserves. [source]

The sugar porter gene family of Laccaria bicolor: function in ectomycorrhizal symbiosis and soil-growing hyphae

NEW PHYTOLOGIST, Issue 2 2008
Mónica Fajardo López
Summary ,,Formation of ectomycorrhizas, a symbiosis with fine roots of woody plants, is one way for soil fungi to overcome carbohydrate limitation in forest ecosystems. ,,Fifteen potential hexose transporter proteins, of which 10 group within three clusters, are encoded in the genome of the ectomycorrhizal model fungus Laccaria bicolor. For 14 of them, transcripts were detectable. ,,When grown in liquid culture, carbon starvation resulted in at least twofold higher transcript abundances for seven genes. Temporarily elevated transcript abundance after sugar addition was observed for three genes. Compared with the extraradical mycelium, ectomycorrhiza formation resulted in a strongly enhanced expression of six genes, of which four revealed their highest observed transcript abundances in symbiosis. A function as hexose importer was proven for three of them. Only three genes, of which just one was expressed at a considerable level, revealed a reduced transcript content in mycorrhizas. ,,From gene expression patterns and import kinetics, the L. bicolor hexose transporters could be divided into two groups: those responsible for uptake of carbohydrates by soil-growing hyphae, for improved carbon nutrition, and to reduce nutrient uptake competition by other soil microorganisms; and those responsible for efficient hexose uptake at the plant,fungus interface. [source]

Arbuscular mycorrhizal fungi respond to the substrate pH of their extraradical mycelium by altered growth and root colonization

NEW PHYTOLOGIST, Issue 1 2002
Ingrid M. Van Aarle
Summary ,,To test the response of arbuscular mycorrhizal (AM) fungi to a difference in soil pH, the extraradical mycelium of Scutellospora calospora or Glomus intraradices, in association with Plantago lanceolata, was exposed to two different pH treatments, while the root substrate pH was left unchanged. ,,Seedlings of P. lanceolata, colonized by one or other of the fungal symbionts, and nonmycorrhizal controls, were grown in mesh bags placed in pots containing pH-buffered sand (pH around 5 or 6). The systems were harvested at approximately 2-wk intervals between 20 and 80 d. ,,Both fungi formed more extraradical mycelium at the higher pH. Glomus intraradices formed almost no detectable extraradical mycelium at lower pH. The extraradical mycelium of S. calospora had higher acid phosphatase activity than that of G. intraradices. Total AM root colonization decreased for both fungi at the higher pH, and high pH also reduced arbuscule and vesicle formation in G. intraradices. ,,In conclusion, soil pH influences AM root colonization as well as the growth and phosphatase activities of extraradical mycelium, although the two fungi responded differently. [source]