Mycelium

About: Mycelium is a research topic. Over the lifetime, 8923 publications have been published within this topic receiving 170993 citations.

Inhibitory Effects of Linear Lipopeptides From a Marine Bacillus subtilis on the Wheat Blast Fungus Magnaporthe oryzae Triticum.

Abstract: Wheat blast is a devastating fungal disease caused by a filamentous fungus, Magnaporthe oryzae Triticum (MoT) pathotype, which poses a serious threat to food security of South America and South Asia. In the course of screening novel bioactive secondary metabolites, we found that some secondary metabolites from a marine Bacillus subtilis strain 109GGC020 remarkably inhibited the growth of M. oryzae Triticum in vitro at 20 μg/disk. We tested a number of natural compounds derived from microorganisms and plants and found that five recently discovered linear non-cytotoxic lipopeptides, gageopeptides A-D (1-4) and gageotetrin B (5) from the strain 109GGC020 inhibited the growth of MoT mycelia in a dose-dependent manner. Among the five compounds studied, gageotetrin B (5) displayed the highest mycelial growth inhibition of MoT followed by gageopeptide C (3), gageopeptide D (4), gageopeptide A (1), and gageopeptide B (2) with minimum inhibitory concentrations (MICs) of 1.5, 2.5, 2.5, 10.0, and 10.0 μg/disk, respectively. Application of these natural compounds has also completely blocked formation of conidia in the MoT fungal mycelia in the agar medium. Further bioassay revealed that these compounds (1-5) inhibited the germination of MoT conidia and, if germinated, induced deformation of germ tube and/or abnormal appressoria. Interestingly, application of these linear lipopeptides (1-5) significantly suppressed wheat blast disease on detached wheat leaves. This is the first report of the inhibition of mycelial growth, conidiogenesis, conidial germination, and morphological alterations in the germinated conidia and suppression of wheat blast disease by linear lipopeptides from the strain of B. subtilis. A further study is needed to evaluate the mode of action of these natural compounds for considering them as biopesticides for managing this notorious cereal killer.

Effect of Fungal Hyphae on the Access of Bacteria to Phenanthrene in Soil

Abstract: The effect of fungal hyphae on the mobilization of soil-dwelling bacteria and their access to hydrophobic phenanthrene in soil was tested in columns containing air-filled agricultural soil. The experimental design included a spatial separation between zones of bacterial inoculation and contamination. Motile Pseudomonas putida PpG7 (NAH7) and fast-growing, hydrophilic Pythium ultimum were used as the model phenanthrene-degrading and vector organisms, respectively. Efficient translocation of strain PpG7 in the range of centimetres in presence of P. ultimum indicated that the fungal mycelia bridged air-filled pores and thereby provided a continuous network of water-paths that enabled bacteria to spread in the soil. Biodegradation of the soil-associated phenanthrene was found only in the presence of the fungal mycelia, hence proving that the fungal network facilitated the access of the bacteria to the contaminant. Our data suggest that the specific stimulation of indigenous fungi is a promising method to mobilize pollutant degrading bacteria and thereby improve soil bioremediation in-situ.

Carbon transfer between plants and its control in networks of arbuscular mycorrhizas

Abstract: 1. Two studies using the stable-isotope 13C have shown that large amounts of carbon can move between plants linked by arbuscular mycorrhizal fungi. Quantities comparable to the carbon cost of the symbiosis for an individual plant may be transferred. 2. We measured C transfer between linked plants of the grass Cynodon dactylon (C4, δ13C ≈– 14‰) and the herb Plantago lanceolata (C3, δ13C ~ – 28‰). To test the hypothesis that the carbon transferred between plants remained in fungal structures at all times, plants were grown for two harvests; at the first harvest they were clipped to ground level, so that shoot re-growth required the transport of carbon from the roots. We also tested the influence of the direction of growth of the fungus, to determine whether C was transported out of or into a newly colonized root, and of growing plants in elevated CO2, to increase the availability of carbon compounds in the roots. 3. Large amounts of C were transferred between linked plants, more so into Plantago than into Cynodon roots. Transfer occurred whether root systems were separated by a 20 μm mesh, that excluded roots but not hyphae, or a 0·45 μm mesh, intended to act as a barrier to hyphae as well. We believe that the high root densities achieved in the experiment allowed hyphae to cross the finer mesh between the two dense root mats. 4. Clipping the plants did not result in any movement of C from roots to shoots, thus confirming the prediction that all C transferred remains in fungal structures. 5. The direction of growth of the fungus did not affect the direction of transfer, nor did the CO2 concentration in which the plants were grown. 6. The amount of C transferred was a positive correlate of the frequency of vesicles in the roots but a negative correlate of the frequency of hyphae. If C were moving into developing colonization units, thus effectively giving the plant a ‘free’ symbiosis, the correlation with internal hyphae should be positive. The positive correlation with vesicles suggests that C is moving into fungal storage structures. 7. We propose a mycocentric view of the phenomenon of interplant C transfer, in which the fungal colonies within roots are seen as parts of an extended mycelium between which the fungus moves resources depending on the dynamics of its own growth. We do not believe that the transfer has an impact on plant C budgets or fitness, but that it may be a major element in the understanding of fungal C budgets.

Truffles Regulate Plant Root Morphogenesis via the Production of Auxin and Ethylene

Abstract: Truffles are symbiotic fungi that form ectomycorrhizas with plant roots. Here we present evidence that at an early stage of the interaction, i.e. prior to physical contact, mycelia of the white truffle Tuber borchii and the black truffle Tuber melanopsorum induce alterations in root morphology of the host Cistus incanus and the nonhost Arabidopsis (Arabidopsis thaliana; i.e. primary root shortening, lateral root formation, root hair stimulation). This was most likely due to the production of indole-3-acetic acid (IAA) and ethylene by the mycelium. Application of a mixture of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and IAA fully mimicked the root morphology induced by the mycelium for both host and nonhost plants. Application of the single hormones only partially mimicked it. Furthermore, primary root growth was not inhibited in the Arabidopsis auxin transport mutant aux1-7 by truffle metabolites while root branching was less effected in the ethylene-insensitive mutant ein2-LH. The double mutant aux1-7;ein2-LH displayed reduced sensitivity to fungus-induced primary root shortening and branching. In agreement with the signaling nature of truffle metabolites, increased expression of the auxin response reporter DR5∷GFP in Arabidopsis root meristems subjected to the mycelium could be observed, confirming that truffles modify the endogenous hormonal balance of plants. Last, we demonstrate that truffles synthesize ethylene from l-methionine probably through the α-keto-γ-(methylthio)butyric acid pathway. Taken together, these results establish the central role of IAA and ethylene as signal molecules in truffle/plant interactions.