Showing papers on "Mycelium published in 1992"
TL;DR: It is suggested that nitrogen deposition from the atmosphere may damage the function of mycorrhiza even before root tip studies reveal any decline in the symbiotic state, and moderate nitrogen fertilization of forest land unaffected by nitrogen pollution is likely to have only passing effects on my Corrhizal development.
Abstract: summary
The effect of excess nitrogen alone, and in combination with phosphorus and magnesium starvation, on the production of extramatrical mycelium was studied in Scots pine seedlings ectomycorrhizal with Laccaria bicolor (R. Mre.) Orton, Hebeloma crustuliniforme (Bull, ex St-Amans) Quel. and Suillus bovinus (L. ex Fr.) O. Kuntze. Seedlings were grown in a semi-hydroponic cultivation system and the ergosterol assay was used to estimate fungal biomass. The mycelial biomass increased rapidly when N was kept low (10–20 mg l−1) and in balance with other nutrients, but no extramatrical mycelium was produced when the N concentration was raised to 200 mg l−1. The growth of the extramatrical mycelium resumed when the excess N treatment was terminated and the seedlings were returned to a low nutrient regime, Laccaria showing more complete resumption of growth than Suillus, while Hebeloma had a low production of extramatrical mycelium in all treatments. Compared with the external mycelium, the amount of fungal tissue on the mycorrhizal roots (mantle and Hartig net) was much less affected by the high N treatment. P starvation increased the production of extramatrical mycelium tenfold, with almost no difference between high and low N nutrient regimes, while Mg starvation had no effect on the fungal biomass. The high N treatment lowered P and particularly Mg concentration of the needles, regardless of the mycorrhizal status of the plant.
It is suggested that nitrogen deposition from the atmosphere may damage the function of mycorrhiza even before root tip studies reveal any decline in the symbiotic state. On the other hand, moderate nitrogen fertilization of forest land unaffected by nitrogen pollution is likely to have only passing effects on mycorrhizal development.
230 citations
TL;DR: The extent of internal root colonization by G. intraradix was relatively limited, but it was sufficient to permit the in vitro formation of hundreds of new spores free of contaminants, which were viable and capable of colonizing host roots.
Abstract: The entire vegetative life cycle of the vesicular-arbuscular mycorrhizal fungus Glomus intraradix was followed in a simple monoxenic culture system using Ri T DNA-transformed carrot roots and nontransformed tomato roots as plant partners. Fungal development, from the growth of initial germ tubes to the formation of an external mycelium network and spore production, was observed nondestructively using light microscopy. Surface-sterilized spores isolated from pot culture constituted an excellent source of fungal inoculum. These spores germinated readily on the nutrient medium and only a low rate of contamination was recorded. Germ tubes approaching the surface of isolated roots changed their growth pattern and branched profusely in response to root factors. Throughout the growth process it was possible to observe directly the formation of terminal and intercalary secondary spores, numerous hyphal anastomoses and arbuscle-like structures, intracellular vesicles and spores. The extent of internal root colonization by G. intraradix was relatively limited, but it was sufficient to permit the in vitro formation of hundreds of new spores free of contaminants, which were viable and capable of colonizing host roots.
200 citations
TL;DR: Sclerotia are loosely described as morphologically variable, nutrient-rich, multihyphal structures which can remain dormant or quiescent when their environment is adverse and then, when conditions improve, germinate to reproduce the fungus.
170 citations
TL;DR: C. minitans will survive and spread in soil for at least 2 yr and continue to give some control of disease but details of its ecology are still uncertain, and the reasons for the lack of commercial interest in this biological control agent are discussed.
156 citations
TL;DR: The possibility that on Zn-polluted soils ectomycorrhizal species and strains are selected that are ZN-tolerant and, in addition, are able to protect their own energy source, the autobiont, from toxicity is discussed.
Abstract: Six strains of ectomycorrhizal fungi were compared for their ability to increase zinc tolerance in Pinus sylvestris L. seedlings. Pioneer and ‘late-stage’ fungi as well as one strain collected from a Zn-polluted site were included in the study. The accumulation of zinc in the host plants was determined at two different sublethal substrate Zn concentrations. The mycobionts varied considerably in their protection of the autobionts against zinc toxicity. Several fungal species reduced zinc accumulation in the pine seedlings. A Thelephora terrestris (Ehrh.) Fr. Strain, however, increased the Zn concentration in its host plants. Specific zinc-retaining capacity of the mycelium and density of the extramatrical mycelium were important features determining the effectiveness of the zinc retention in the fungal symbiont.
142 citations
TL;DR: The existence of an important negative correlation between the extent of the fungal development and the growth of the host plants is demonstrated and it is suggested that also nitrogen acquisition by the plants might be altered by the fungus.
Abstract: SUMMARY Nine ectomycorrhizal fungi have been studied for their effect on the growth of Pinus sylvestris L. seedlings. The plants were kept growing for six months in root chambers with a changeable volume. All seedlings were cultivated under conditions of low substrate nutrient concentrations and they became strongly infected within a short time. We demonstrated the existence of an important negative correlation between the extent of the fungal development and the growth of the host plants. In most studies this reduced growth is attributed to an energy drain by the fungus. Fungi producing large amounts of fungal tissue are more energy consuming than species which only develop a sparse mycelium. However we suggest that also nitrogen acquisition by the plants might be altered by the fungus. Certain fungi probably retain a considerable amount of nitrogen for their own growth, thus reducing the amount transported to the host plant. A decreased N transport finally results in a slower growth. In this study the extramatrical mycelium in the rooting substrate was determined by wet oxidation and by nitrogen determination. This component of the fungal biomass showed the biggest variation among the different mycobiont species. The results are discussed in relation to the culture technique employed.
133 citations
TL;DR: Fumiquinazolines A, B and C, exhibiting moderate cytotoxicity, were isolated from the mycelium of a strain of Aspergillus fumigatus which existed in the gastrointestinal tract of the saltwater fish Pseudolabrus japonicus.
107 citations
TL;DR: A lichen-specific secondary pathway was consistently induced in a lichen fungus (Cladonia grayi) grown in the absence of the alga and secondary productivity was comparable to that of some nonlichen fungi.
101 citations
TL;DR: The effects of mutations in the FBF and THN genes indicate that these differentially regulated hydrophobins may play a key role in the emergence of aerial structures while different hydrophOBins may determine specific hyphal-surface properties.
86 citations
TL;DR: The edible basidiomycete, Agaricus bisporus, produces extracellular endoglucanase, which is differentially regulated by the carbon source of the culture medium, and a strong bias against codons ending with G and A was observed.
77 citations
TL;DR: Six saprophytic fungi belonging to different genera and isolated from three organic substrates were tested under controlled in vitro conditions for their effect on the germination of Glomus mosseae and the development of vesicular-arbuscular mycorrhizal fungal (VAMF) mycelium.
Abstract: Six saprophytic fungi belonging to different genera and isolated from three organic substrates were tested under controlled in vitro conditions for their effect on the germination of Glomus mosseae (Nicol & Gerd) Gerd & Trappe resting spores and on the development of vesicular-arbuscular mycorrhizal fungal (VAMF) mycelium The development of G mosseae was stimulated by sterile water extracts from organic substrates and by the presence of Trichoderma spp isolated from these substrates Microbial inoculation did not affect the percentage of spore germination, which reached 90–95% after 26 days' incubation, but the germination rate was hastened and the development of VAM mycelium from germinated spores was enhanced by the presence of Trichoderma spp Stimulation caused by Trichoderma might be attributed to the production of volatile compounds more than to non-volatile compounds released to the growing media No hyphal contact between both types of fungi was necessary to detect stimulation in dual inoculation treatments The other saprophytes tested inhibited spore germination
TL;DR: This chapter describes isozyme methods for the analysis of vesiculararbuscular and ectomycorrhizal fungi and for the identification and quantification of mycorrhIZal fungi within plant roots and highlights standardization of extracts.
Abstract: Publisher Summary This chapter describes isozyme methods for the analysis of vesiculararbuscular and ectomycorrhizal fungi and for the identification and quantification of mycorrhizal fungi within plant roots Present areas of application are reviewed briefly As vesicular-arbuscular mycorrhizal fungi cannot be cultured axenically, fungal material in the form of resting spores or external and/or internal root mycelium, together with surface-cleaned infected root systems, are routinely analyzed The chapter further highlights standardization of extracts To standardize the amount of extracts for quantitative studies, two methods should be considered: dry weight and protein content Unlike the fungi forming vesicular-arbuscular mycorrhizal associations, it is possible to culture many of the ectomycorrhizal fungi, particularly members of many Ascomycete and Basidiomycete families The production of taxonomically recognizable fruiting structures (also a source of extractable tissue) makes it possible to isolate dikaryotic and, in certain cases, monokaryotic mycelium from individuals of the same species The chapter also explains ectomycorrhizal sample preparation
TL;DR: A clear relation between Cd tolerance and site origin of the isolates did not exist, although such a relationship was found when strains are compared within one species, and wide differential response to Cd was obtained between the individual species.
Abstract: Eleven strains of ectomycorrhizal fungi belonging to seven species have been cultured on a cadmium-contaminated growth medium in order to determine their in vitro cadmium tolerance. Four strains were collected from a zinc and cadmium-polluted soil. Radial growth rate was a sensitive parameter to detect Cd toxicity. A wide differential response to Cd was obtained between the individual species. A clear relation between Cd tolerance and site origin of the isolates did not exist, although such a relationship was found when strains are compared within one species. Cd-sensitive and Cd-tolerant strains of Suillus bovinus were studied in more detail. Two isolates were grown on media with combinations of two non-toxic zinc concentrations and three cadmium levels. Adding a higher Zn concentration to the medium resulted in a reduction of the toxic effect of Cd. This antagonistic effect also resulted in a lowered Cd concentration in the mycelium.
TL;DR: Analysis of the haemagglutinating activity in various cell fractions indicated that the protein was associated with extracellular polymer layers and with the cell wall of the fungus.
Abstract: Several studies have indicated that the capture of nematodes by the nematophagous fungus Arthrobotrys oligospora is mediated by a lectin on the fungal surface. One of the major surface proteins of this fungus showed haemagglutinating activity and was isolated by affinity chromatography using a mucin Sepharose column. Biochemical analysis showed that the protein was a dimeric glycoprotein with a molecular mass of 36 kDa and an isoelectric point of pH 6.5, and contained no sulphur amino acids. The protein was N-terminally blocked; four internal peptides were sequenced, and showed no significant similarity to sequences in the Swiss-Prot or PIR databases. The haemagglutinating activity of the isolated protein was not inhibited by any of the mono- or disaccharides tested, but it was inhibited by the glycoproteins fetuin and mucin. The haemagglutinating activity changed after incubating the protein in buffers of different pH, with maximal activity at pH 11.0 and no activity at pH 2.8. The lectin was tested for different enzymic activities but none were detected. Analysis of the haemagglutinating activity in various cell fractions indicated that the protein was associated with extracellular polymer layers and with the cell wall of the fungus. About the same amount of the haemagglutinating protein was recovered from samples of vegetative mycelium and of mycelium containing nematode-trapping cells.
TL;DR: The results are discussed in relation to phosphate accumulation and translocation by the extramatrical mycelium of ectomycorrhizas in soil.
TL;DR: Conditions promoting a well-dispersed mycelium suitable for studying the physiological control of secondary metabolism also supported the formation of 5-hydroxy-4-oxonorvaline by S. akiyoshiensis.
Abstract: Most media in which the growth of shaken submerged cultures of Streptomyces akiyoshiensis was examined did not support the formation of well-dispersed mycelial suspensions. Investigation of the culture conditions promoting dispersed growth showed the pH of the culture medium to be of critical importance; an initial value of 5.5 minimized aggregation of the mycelium while supporting adequate biomass production. In cultures started at this pH, spore inocula gave better mycelial dispersal than did vegetative inocula; with spore inocula, growth morphology was also less affected by inoculum size. The composition of the nutrient solution influenced the extent of mycelial dispersal; slow growth was often associated with clumping but no clear correlation was observed between pellet formation and the ability of carbon or nitrogen sources to support rapid growth. Increasing the phosphate concentration from 0.5 to 15 mM caused a modest decrease in mycelial aggregation. Conditions promoting a well-dispersed mycelium suitable for studying the physiological control of secondary metabolism also supported the formation of 5-hydroxy-4-oxonorvaline by S. akiyoshiensis.
TL;DR: These reported effects either are specific for the Eucalyptus-Pisolithus symbiosis or simply represent artifacts, which is suggested by a comparison of the experimental approaches.
Abstract: Fungal mycelium of the fly agaric (Amanita muscaria [L. ex Fr.] Hooker), and inoculated or noninoculated seedlings of Norway spruce (Picea abies [L.] Karst.) were grown aseptically under controlled conditions. In order to detect symbiosis-specific polypeptides (‘ectomycorrhizins’, see Hubert and Martin, 1988, New Phytol.110, 339–346) the protein patterns of (i) fungal mycelium, (ii) mycorrhizal, and (iii) non-mycorrhizal root tips were compared by means of one- and twodimensional electrophoresis on a microscale. Because of the sensitivity of these micromethods (50 and 200 ng of protein, respectively), single mycorrhizal root tips and even the minute quantities of extramatrical mycelium growing between the roots of inoculated plants could be analysed. Differences in the protein patterns of root tips could be shown within the root system of an individual plant (mycorrhizal as well as non-mycorrhizal). In addition, the protein pattern of fungal mycelium grown on a complex medium (malt extract and casein hydrolysate) differed from that of extramatrical mycelium collected from the mycorrhiza culture (pure mineral medium). Such differences in protein patterns are obviously due to the composition of the media and/or different developmental stages. Consequently, conventional analyses which use extracts of a large number of root tips, are not suitable for differentiating between these effects and symbiosis-specific differences in protein patterns. In order to detect ectomycorrhizins, it is suggested that roots and mycelium from individual, inoculated plants should be analysed. This approach eliminates the influence of differing media, and at the same time allows a correct discrimination between developmental and symbiosisspecific changes. In our gels we could only detect changes in spot intensity but could not detect any ectomycorrhizins or the phenomenon of polypeptide ‘cleansing’, which both characterize theEucalyptus-Pisolithus symbiosis (Martin and Hubert, 1991, Experientia47, 321–331). We thus suggest that these reported effects either are specific for theEucalyptus-Pisolithus symbiosis or simply represent artifacts. The latter point of view is strengthened by a comparison of the experimental approaches.
TL;DR: Some of the cellulase activities detected in VAM roots were attributed to the fungus, since endoglucanase activity found in the external mycelium of G. mosseae and in mycorrhizal root extracts showed the same electrophoretic mobility.
Abstract: summary
Production of endoglucanase (EC 3.2.1.4) and exoglucanase (EC 3.2.1.91) enzymes was studied during penetration of the host and development of the vesicular-arbuscular mycorrhizal (VAM) fungus, Glomus mosseae, in roots of lettuce (Lactuca sativa) and onion (Allium cepa). Endo- and exoglucanase activities increase in VAM plants at the beginning of entry-point formation and arbuscule development. No relationship was found between the number of vesicles and endo- and exoglucanase activities. Extracts from spores and external mycelium of G. mosseae had endo- and exoglucanase activities. Some of the cellulase activities detected in VAM roots were attributed to the fungus, since endoglucanase activity found in the external mycelium of G. mosseae and in mycorrhizal root extracts showed the same electrophoretic mobility.
TL;DR: The most suitable conditions for protoplasting were as follows: age of the organism in slant, 3 days; mycelium age, 20 h; volume of lytic enzymes, 190 ml;Mycelial weight (dry equivalent), 1.66 g; time of contact with lytic enzyme, 2 h; temperature of protoplasts, 30°C; phosphate buffer, 25 m m , pH 6.5; KCl as osmotic stabilizer, 0.7 m
TL;DR: A mucilaginous polysaccharide (N-PS) prepared from the liquid cultured mycelial broth of the fungus, consisted of (1→6)-;(1→3)-β-D-glucopyranan as discussed by the authors.
Abstract: Some polysaccharides extracted from ningyotake, the fruiting body of Polyporous confluens, with hot water (100°C, FI), 1% ammonium oxalate solution (100°C, FII), and 5% sodium hydroxide solution (80°C, FIII) in that order. These polysaccharide fractions were further fractionated by ethanol precipitation and gel filtration on the column of Toyopearl HW-65F with 0.3 M sodium hydroxide solution.A strong antitumor activity were found in five xyloglucan-protein complexes, FI-2-a, -b, -c; FII-2-a, and FIII-2-a.Analyses of physico-chemical properties and IR- and NMR-spectra of these active fractions showed that their main components were (1→3)-;(1→6)-β-D-glucopyranans containing a small amount of xylose residues and 2–3% of protein.A mucilaginous polysaccharide (N-PS) prepared from the liquid cultured mycelial broth of the fungus, consisted of (1→6)-;(1→3)-β-D-glucopyranan. Antitumor activities were also found in a subfraction that was purified from N-PS by gel filtration.Also, a strong antitumor activity was fo...
TL;DR: The yeast-mycelium dimorphism in Ceratocystis ulmi, the causative agent of Dutch elm disease, was switched by gossypol, nordihydroguaiaretic acid, and propylgallate.
Abstract: The yeast-mycelium dimorphism in Ceratocystis ulmi, the causative agent of Dutch elm disease, was switched by gossypol, nordihydroguaiaretic acid, and propylgallate. In each case the mycelial form was converted to the yeast form. These compounds are recognized lipoxygenase inhibitors. Inhibitors of cyclooxygenase and thromboxane synthetase did not cause mycelia to shift to the yeast form. We suggest the following two-part hypothesis: (i) that lipoxygenase is a target for antifungal antibiotics and (ii) that many phytoalexins (antimicrobial compounds of plant origin) are targeted toward fungal lipoxygenases. In addition, in a study to determine potential lipoxygenase substrates, a fatty acid analysis indicated that C. ulmi conidiospores contained high levels of oleic, linoleic, and linolenic acids but no arachidonic acid.
TL;DR: The range of morphological forms of actinomycetes in shaken flask culture and fermenters is reviewed and the relationship between morphology and production of antibiotics and other metabolites is examined.
Abstract: The range of morphological forms of actinomycetes in shaken flask culture and fermenters is reviewed. Some of the factors that influence pellet formation and its prevention are discussed. The relationship between morphology and production of antibiotics and other metabolites is also examined.
TL;DR: Methods for measuring populations and understanding the behavior of vesicular-arbuscular mycorrhizal fungi growing in association with plants and soil in field-based, glasshouse or laboratory studies are emphasized.
Abstract: Publisher Summary This chapter emphasizes methods for measuring populations and understanding the behavior of vesicular-arbuscular mycorrhizal fungi growing in association with plants and soil in field-based, glasshouse or laboratory studies. The methods are a basis for developing procedures for each set of circumstances for vesicular-arbuscular mycorrhizal fungi to affect a role contributing to the production of crops. Plants on revegetation sites or to species abundance and speciation of natural plant populations, they must influence the survival, growth or reproductive output of their hosts. The effects of mycorrhiza on plant development are greatly influenced by the timing and amount of mycorrhiza formation. The chapter further describes propagule phase. An individual mycelium arising from a discrete propagule such as a spore can be distinguished at an early stage in colonization of roots. At later stages, all the colonization by a fungus in a root or roots of a plant would have to be regarded as a unit if there are no markers to distinguish the mycelium. The same reasoning applies to extraradical (extramatrical) hyphae. This is a necessary simplification of differentiating individuals for some life-history stages of fungi for the present. Propagule germination or regrowth and interception of roots and colony formation are also illustrated.
Journal Article•
TL;DR: It is demonstrated that sublethal concentrations of propionic acid stimulated aflatoxin production considerably in submerged shaken culture and solid substrate culture of Aspergillus flavus and in liquid conditions a flatoxin formation was significantly influenced by the time of addition of Propionic acid.
Abstract: The present experiments demonstrate that sublethal concentrations of propionic acid stimulated aflatoxin production considerably in submerged shaken culture and solid substrate culture of Aspergillus flavus. In liquid conditions aflatoxin formation was significantly influenced by the time of addition of propionic acid. The spores initially swelled into large spherical cells, and the resultant hyphae developed into a swollen, stunted, and excessively branched mycelium.
TL;DR: In permissive media, with nitrogen sources that permitted relatively high growth rates, sporulation was conditioned to the consumption of ammonium in the medium, but not to that of other nitrogen sources, such as asparagine.
Abstract: Streptomyces antibioticus ETHZ 7451 formed spores in cultures grown in a liquid medium from either a spore or a mycelium inoculum. The spores formed were similar to those formed on surface-grown cu...
TL;DR: Self-fertile isolates of Phytophthora infestans would appear to be intimate mixtures of A1 and A2 hyphae, however, results also indicate that heterokaryons/heteroplasmons occurred at a low frequency.
TL;DR: It is found that in the presence of host plant cells or some antagonistic fungi, the highly forest-pathogenic basidiomycete Armillaria ostoyae is strongly stimulated to produce a series of toxic secondary metabolites which are capable of inhibiting the growth of the antagonist or of killing the plant cells still before cell contact.
Abstract: We found that in the presence of host plant cells or some antagonistic fungi, the highly forest-pathogenic basidiomycete Armillaria ostoyae is strongly stimulated to produce a series of toxic secondary metabolites which are capable of inhibiting the growth of the antagonist or of killing the plant cells still before cell contact. The chemical structures of the metabolites have been identified, of which two of them are new compounds. The time dependence and sites of synthesis in the mycelium have been determined in order to lay the foundation for future studies concerning the induction mechanism for the synthesis of the toxins.
TL;DR: Pseudomonas cepacia, a common soil and rhizosphere inhabitant, showed strong antagonism against several fungal plant pathogens, and in dual cultures it greatly restricted the growth and conidial formation in several of these fungi.
Abstract: Pseudomonas cepacia, a common soil and rhizosphere inhabitant, showed strong antagonism against several fungal plant pathogens. In dual cultures it greatly restricted the growth and conidial formation in several of these fungi. Growth restriction was associated with the frequent induction of a variety of morphological abnormalities such as chlamydoconidium formation, hyphal swellings, vacuolation and granulation of the mycelial contents, as well as lysis of hyphae and conidia. The induction of these deleterious morphological changes in fungi and inhibition of conidial formation were also found with a crude preparation of an antifungal compound fromP. cepacia. Mutants, defective in the production of this antifungal compound, failed to induce these morphological changes; this suggests that the antifungal compound is responsible for these abnormalities.
TL;DR: The growth-promoting effect of the thermophilic fungus Scytalidium thermophilum in mushroom compost on the mycelium of the edible mushroom Agaricus bisporus was investigated but it was demonstrated that hyphal extension rates were not clearly related to mushroom biomass increase rates.
Abstract: The growth-promoting effect of the thermophilic fungus Scytalidium thermophilum in mushroom compost on the mycelium of the edible mushroom Agaricus bisporus was investigated. Results obtained by others were confirmed by showing that S. thermophilum leads to an increased hyphal extension rate of the mushroom mycelium. However, it was demonstrated that hyphal extension rates were not clearly related to mushroom biomass increase rates. A number of experiments pointed strongly towards CO2 as the determinant of hyphal extension rates. In compost, CO2 is produced mainly by thermophilic fungi. Several experiments did not reveal any other specific compound produced by S. thermophilum that increases the hyphal extension rate of the mushroom mycelium.