Mycelium

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

Selection of Streptomyces against soil borne fungal pathogens by a standardized dual culture assay and evaluation of their effects on seed germination and plant growth

Abstract: In the search for new natural resources for crop protection, streptomycetes are gaining interest in agriculture as plant growth promoting bacteria and/or biological control agents. Because of their peculiar life cycle, in which the production of secondary metabolites is synchronized with the development of aerial hyphae and sporulation, the commonly used methods to screen for bacterial antagonists need to be adapted. The dual culture assay was standardized in terms of inoculation timing of Streptomyces antagonist and pathogen, and growth rate of different fungal pathogens. In case of fast-growing fungi, inoculation of the antagonist 2 or 3 days prior to the pathogen resulted in significantly stronger inhibition of mycelium growth. One hundred and thirty Streptomyces strains were evaluated against six destructive soil borne pathogens. The activity of strains varied from broad-spectrum to highly specific inhibition of individual pathogens. All strains inhibited at least one tested pathogen. Three strains, which combined the largest broad-spectrum with the highest inhibition activity, were selected for further characterization with four vegetable species. All of them were able to colonize seed surface of all tested vegetable crops. They mostly improved radicle and hypocotyl growth in vitro, although no statistically significant enhancement of biomass weight was observed in vivo. Occasionally, transient negative effects on germination and plant growth were observed. The adapted dual culture assay allowed us to compare the inhibition of individual Streptomyces strains against six fungal soil borne pathogens. The best selected strains were able to colonize the four vegetable crops and have a potential to be developed into biocontrol products. Although they occasionally negatively influenced plant growth, these effects did not persist during the further development. Additional in vivo studies are needed to confirm their potential as biological control or plant growth promoting agents.

Direct observation of fungal aggregates in sand dune soil.

Abstract: The mycorrhizal fungus Glomus in association with bean hosts, Phaseolus vulgaris L., growing in pot cultures and grass hosts, Calamovilfa longiflora (Hook.) Scribn and Andropogon sp. growing on Lake Huron sand dunes produced extensive external mycelium. This mycelium was the dominant factor in the aggregation of soil particles. Light and scanning electron microscope studies indicated that the sand grains were attached to the hyphae. An amorphous deposit was often present at the interfaces of sand grains and hyphae. It appeared to act as an adhesive. Staining procedures indicated that this material contained polysaccharide. Other microorganisms were observed in association with the Glomus hyphae and the amorphous deposits.

Antitumor Active Protein-containing Glycans from the Chinese Mushroom Songshan Lingzhi, Ganoderma tsugae Mycelium

Abstract: A water-soluble polysaccharide, FI, extracted from the mycelium of Granoderma tsugae, was fractionated and purified by ion-exchange chromatography, gel filtration, and affinity chromatography. Sixteen polysaccharides obtained were examined for antitumor effects on Sarcoma 180 in mice. The three active polysaccharides obtained were as follows: FIo-a: A glycan-protein complex containing 9.3% protein, and having a hetero-glyco-chain of mannose and xylose. FIo-b-alpha: Molecular weight 10,000, glucan-protein complex containing 25.8% protein. The inhibition ratio was 61.8% against the solid cancer Sarcoma 180/mice; the survival ratio was more than 194% of the control group (100). FA-1-b-alpha: Molecular weight 16,000, a complex of glycan:protein = 42:58 w/w, consisting of glucose as a main component, and associated with arabinose, mannose, xylose, and galactose. This had a tumor inhibition ratio of 56% and a survival ratio of more than 182%. Comparison of active glycan with the fruiting body and mycelium: Among water-soluble polysaccharides of fruiting body, FIo-a and FA-1, with antitumor activity, were both glucogalactan-protein complexes of molecular weight 10,000, but that of mycelium was a homoglucan protein complex in FIo-b-alpha and heteroglucan protein in both FA-1-a and FA-1-b-alpha. The heteroglucan had a low tumor inhibition ratio, but caused a high survival ratio in mice.

Role of antibiosis in suppression of charcoal rot disease by soybean endophyte Paenibacillus sp. HKA-15.

Abstract: Four defective (AFM−) mutants of Paenibacillus sp. HKA-15 that no longer produced the peptide antifungal metabolites were developed through ethyl methane sulfonate (EMS) mutagenesis and used for in vivo experimentation. Reduced percentage of seed germination by mutants DM1 and DM2 (22.5% and 25%, respectively) and a high percent of disease incidence (69.3% and 67%, respectively) compared to wild-strain HKA-15 (80% seed germination and 27% disease incidence) indirectly indicated the role of peptide metabolite on disease suppression. Plants treated with AFM− clones showed stunted growth and the presence of pepperlike microsclerotia in the stem tissues. Light and scanning electron microscopic studies clearly showed the effect of peptide antibiosis on hyphal morphology. Exposure to crude extracts of antibiotics produced abnormal contraction of fungal cytoplasm, granulation, and fragmentation of hyphal mycelia and cell lysis. The presence of bacterial cells in the lumen of degrading fungal mycelium suggested a direct involvement of Paenibacillus sp. HKA-15 in the lysis of Rhizoctonia bataticola.