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The cellulolytic activity of some soil fungi isolated from soil and decomposing pieces of plant material was observed to depend upon the genera of fungi, the nature of substrate and the temperature. The cellulase produced in the presence of cellulose powder was active against CMC and vice versa.
Ramihyphin A at subfungistatic concentrations stimulates ramification of hyphae of filamentous fungi. Stimulation of terminal ramification of hyphae that can be observed particularly in phytopathogenic fungi is most frequent. Hyphae of Microsporon canis, Trichophyton mentagrophytes, Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum ramify intensively laterally. Stimulation of the lateral ramification was observed in Monilia fructigena, Penicillium marneffei and Penicillium chrysogenum. The antibiotic induces also formation of vesicular structures in phytopathogens. Due to the substantial ramification of hyphae, both terminal and lateral, the growth of colonies is interrupted. The addition of the antibiotic to a growing colony of Botrytis cinerea induces dichotomic ramification of terminal hyphae after 3 h of growth. Lateral hyphae begin to grow later and further ramify dichotomically. Dense bundles of ramified hyphae are formed after 24 h due to the unbalanced ramification and the colony no longer increases its size.
A simple method of isolation and purification of cultures of higher fungi, mainly wood-rotting fungi, without special requirements for the presence of nitrogencontaining nutrients is described. Parts of fruiting bodies, spores or infected wood is inoculated on Petri dishes with an agar medium of the following composition: 1.0 g KH2PO4, 0.2 g MgSO4 - 7 H2O, 0.1 g caSO4, 0.01 g Fe2(SO4)3, 10.0 g glucose, tap water to 1 litre; 20.0 g agar. This medium does not suit most of the contaminants but fungal hyphae overgrow the whole surface of the dish so that a purified culture can be obtained from parts distant from the inoculation site.
Nickel (Ni) uptake capability from aqueous solutions was studied in a filamentous fungi strains group of Rhizopus sp., Penicillium sp. Aspergillus sp., Trichoderma sp., Byschoclamyss sp., and Mucor sp. The metal uptake of a Rhizopus sp. strain, which has the highest uptake capacity, was corroborated by electron microscopy; no Ni deposits were observed on the cell wall, but rather a homogeneous accumulation was seen on the cell surface. The influence on the capacity of metal uptake by environmental parameters such as pH, temperature, time, and the interference of other ions in the solution, was also studied. Nickel accumulation by the selected strains is fast, occurring in less than 30 min, and does not require a microorganism's active metabolism to take place. The sorption isotherms were established for the selected fungi, in order to determine the maximum metal uptake capacity. The sorption isotherms were fixed to the mathematical models of Freundlich and Langmuir, obtaining better performance on the Langmuir model.
Bacteria Pseudomonas striata, Bacillus polymyxa, B. megaterium and B. pulvifaciens, and fungi Aspergillus awamori, A. niger and Penicillium digitatum dissolve tricalcium phosphate and, much less, Mussorie and Udaipur rock phosphate. The solubilizing power of fungi was higher than that of bacteria, the highest being with A. awamori and A. niger, and with P. striata. Electron microscopy of the various cultures showed an electron-dense layer on the bacterial surface after negative staining. The size of phosphate particles decreased by the microbial action, with tricalcium phosphate from 140--250 to 30--90 nm after three weeks of incubation.
The amylolytic activity and especially the production of alpha-amylase (EC 3.2.1.1) and alpha-glucosidase (EC 3.2.1.20) was screened in imperfect fungi, mucoral fungi and some ascomycetes. The character of the polysaccharide system, which is responsible for the utilization of alpha (1 to 4) glucan, was specified with a concomitant screening of growth on soluble starch. The amylolytic activity was found in 29 strains out of the 49 tested.
A survey of the filamentous fungi other than the symbiotic one found in association with Atta sexdens rubropilosa colonies was carried out. Different fungal species (27 taxa) were isolated a few days after treating the workers with toxic baits (sulfluramid; Mirex-S), from 40 laboratory and 20 field nests. Syncephalastrum racemosum (54%) and Escovopsis weberi (21%), Trichoderma harzianum (38%) and Fusarium oxysporum (23%) were the prevalent species in laboratory and field nests, respectively. Acremonium kiliense, Acremonium strictum, E. weberi, F. oxysporum, Fusarium solani, Moniliella suaveolens and T. harzianum were found in both nests' groups. We revealed that many filamentous fungi can co-exist in a dormant state inside the nests of these insects and some of them appear to be tightly associated with this environment.
Microscopic fungi of 47 species and 24 genera isolated from radioactive soil and other radioactive substrates of a 10-km alienation zone from Chernobyl Nuclear Power Plant were investigated. Only 19 % of such fungi showed toward the ionizing irradiation source positive radiotropism. Strains with best-defended radiotropism responded to the influence of weak white light. Both of these responses (radiotropism and photostimulation) were of an adaptive nature, were found in both dark-colored and light-colored micromycetes and were probably a strain-related feature.
Various wild-type yeasts and fungi were screened to evaluate their ability to ferment L-arabinose under oxygen-limited conditions when grown in defined minimal media containing mixtures of L-arabinose, D-xylose, and D-glucose. Although all of the yeasts and some of the fungi consumed arabinose, arabinose was not fermented to ethanol by any of the strains tested. Arabitol was the only major product other than cell mass formed from L-arabinose; yeasts converted arabinose to arabitol at high yield. The inability to ferment L-arabinose appears to be a consequence of inefficient or incomplete assimilation pathways for this pentose sugar.
Antifungal activities of the compounds isolated from Kalopanax pictus against representative fungi of dermatomycosis were investigated using paper disc diffusion method. It was found that kalopanaxsaponins A and I were effective in inhibiting the growth of Candida albicans KCTC 1940 and Cryptococcus neoformans KCTC 7224 with minimum inhibitory concentration (MIC) of 25 micrograms/ml. It showed that antifungal activity of both compounds have strong selectivity against the fungi of dermatomycosis.
In co-ordination with the Umweltbundesamt Berlin, the Landesgesundheitsamt Baden-Wurttemberg (LGA) initiated external quality assurance in the diagnosis of indoor fungi in autumn 2001. Four of six fungal strains commonly found indoors have to be fully identified (on the genus and species level). There are two distributions per year; the six distributions hitherto carried out resulted in correct identification by 46-89% of laboratories (40-71 participants, total 148). It is clear from the results that repeat participants were more successful. In addition to the pure cultures sent out we offered actual samples (two air samples, one wood material, one sample of house dust, hitherto); 43- 69% of participating laboratories also took part in this facultative investigation of actual samples and 29-62% were successful. Results that differed considerably revealed problems while treating and evaluating actual samples. Therefore, activities in this field should be enhanced. In conclusion, external quality assurance in the diagnosis of indoor fungi is a useful management aid in the maintenance and improvement of laboratory performance.
Airborne fungal contaminants are increasingly gaining importance in view of health hazards caused by the spores themselves or by microbial metabolites. In addition to the risk for infection, the allergenic and toxigenic properties, as well as the inflammatory effects are discussed in this review as possible health impacts of bioaerosols. A major problem is the lack of threshold values for pathogenic and non-pathogenic fungi, both in the workplace and in outdoor air. While the relevance of mycotoxins has been intensely studied in connection with contamination of food and feed, the possible respiratory uptake of mycotoxins from the air has so far not been sufficiently taken into account. Toxic secondary metabolites are expected to be present in airborne spores, and may thus occur in airborne dust and bioaerosols. Potential health risks cannot be estimated reliably unless exposure to mycotoxins is determined qualitatively and quantitatively. Microbial volatile organic compounds (MVOC) have been suggested to affect human health, causing lethargy, headache, and irritation of the eyes and mucous membranes of the nose and throat. The production of MVOC by fungi has been discussed in connection with domestic indoor microbial pollution, but the relevance of fungal metabolites in working environments remains insufficiently studied.
The cAMP signal transduction pathway controls a wide variety of processes in fungi. For example, considerable progress has been made in describing the involvement of cAMP pathway components in the control of morphogenesis in Saccharomyces cerevisiae, Ustilago maydis, and Magnaporthe grisea. These morphological processes include the establishment of filamentous growth in S. cerevisiae and U. maydis, and the differentiation of an appressorial infection structure in M. grisea. The discovery that appressorium formation requires cAMP signaling provides an immediate connection to fungal virulence. This connection may have broader implications among fungal pathogens because recent work indicates that cAMP signaling controls the expression of virulence traits in the human pathogen Cryptococcus neoformans. In this fungus, cAMP also influences mating, as has been found for Schizosaccharomyces pombe and as may occur in U. maydis. Finally, cAMP and mitogen-activated protein kinase pathways appear to function coordinately to control the response of certain fungi, e.g., Saccharomyces cerevisiae and Schizosaccharomyces pombe, to environmental stress. There are clues that interconnections between these pathways may be common in the control of many fungal processes.
Fungi (Cunninghamella elegans ATCC 9245, Mucor ramannianus R-56, Aspergillus niger VKMF-1119, and Phanerochaete chrysosporium BKMF-1767) were tested to elucidate the biologic fate of the topical insect repellent N,N-diethyl-m-toluamide (DEET). The elution profile obtained from analysis by high-pressure liquid chromatography equipped with a reverse-phase C-18 column, showed that three peaks occurred after incubation of C. elegans, with which 1 mM DEET was combined as a final concentration. The peaks were not detected in the control experiments with either DEET alone or tested fungus alone. The metabolites produced by C. elegans exhibited a molecular mass of 207 with a fragment ion (m/z) at 135, a molecular mass of 179 with an m/z at 135, and a molecular mass of 163 with an m/z at 119, all of which correspond to N,N-diethyl-m-toluamide-N-oxide, N-ethyl-m-toluamide-N-oxide, and N-ethyl-m-toluamide, respectively. M. ramannianus R-56 also produced N, N-diethyl-m-toluamide-N-oxide and N-ethyl-m-toluamide but did not produce N-ethyl-m-toluamide-N-oxide. For the biologic toxicity test with DEET and its metabolites, the freshwater zooplankton Daphnia magna was used. The biologic sensitivity in decreasing order was DEET > N-ethyl-m-toluamide > N,N-diethyl-m-toluamide-N-oxide. Although DEET and its fungal metabolites showed relatively low mortality compared with other insecticides, the toxicity was increased at longer exposure periods. These are the first reports of the metabolism of DEET by fungi and of the biologic toxicity of DEET and its fungal metabolites to the freshwater zooplankton D. magna.
Fungi colonizing fine roots of containerized Picea glauca seedlings were assessed in four large conifer nurseries in northern Alberta. PCR amplification of fungal rDNA (internal transcribed spacer and a portion of the 5' end of the large subunit gene) from random samples of fine feeder roots gave between 1 and 4 amplicons per seedling. Amplicons were either separated by electrophoresis and sequenced directly, or cloned and sequenced. The resulting sequences were compared to sequences obtained from cultures established from seedling roots and from GenBank by maximum parsimony analysis. ITS sequences formed 11 distinct clades, each including at least one reference sequence. The ectomycorrhizal basidiomycetes Thelephora americana and Amphinema byssoides were dominant, whereas ascomycetes were less common. Fungi with sequences similar to members of the Heleotiales which form ericoid mycorrhizas were also present. Correspondence analysis revealed strong positive and negative associations among fungal taxa as well as an influence of applied fertilizer level on fungal diversity and species composition.
The filamentous fungi have dynamic and variable hyphal structures within which cytoplasm can be moved, synthesized, and degraded, in response to changes in environmental conditions, resource availability, and resource distribution. Their study has gone through several phases. In the first phase, direct observation was emphasized without undue concern for interior structures or in the presence of cytoplasm. By the mid-1970s, single biochemical proxies (ergosterol, marker fatty acids, chitin derivatives, etc.) were being used increasingly. The use of these surrogate single measurements continues, in spite of their inability to provide information on the physical structure of the filamentous fungi. Molecular approaches also are being used, primarily through the use of bulk nucleic acid extraction and cloning. Because the sources of the nucleic acids used in such studies usually are not known, taxonomic and phylogenetic information derived by this approach cannot be linked to specific fungal structures. Recently, a greater emphasis has been placed on assessing physical aspects of indeterminate fungal growth, involving the assessment of cytoplasm-filled and evacuated (empty) hyphae. Both of these parameters are important for describing filamentous fungal growth and function. The use of phase contrast microscopy and varied general stains, as well as fluorogenic substrates with observation by epifluorescence microscopy, has made it possible to provide estimates of cytoplasm-filled hyphal lengths. Using this approach, it has been possible to evaluate the responses of the indeterminate fungal community to changes in environmental conditions, including soil management. It is now possible to obtain molecular information from individual bacteria and fungal structures (hyphae, spores, fruiting bodies) recovered from environments, making it possible to link individual fungal structures with their taxonomic and phylogenetic information. In addition, this information can be considered in the context of the indeterminate filamentous fungal lifestyle, involving the dynamics of resource allocation to hyphal structural development and synthesis of cytoplasm. Use of this approach should make it possible to gain a greater appreciation of the indeterminate filamentous fungal lifestyle, particularly in the context of microbial ecology.
The effect of zinc on leaf decomposition by aquatic fungi was studied in microcosms. Alder leaf disks were precolonized for 15 days at the source of the Este River and exposed to different zinc concentrations during 25 days. Leaf mass loss, fungal biomass (based on ergosterol concentration), fungal production (rates of [1-14C]acetate incorporation into ergosterol), sporulation rates, and species richness of aquatic hyphomycetes were determined. At the source of the Este River decomposition of alder leaves was fast and 50% of the initial mass was lost in 25 days. A total of 18 aquatic hyphomycete species were recorded during 42 days of leaf immersion. Articulospora tetracladia was the dominant species, followed by Lunulospora curvula and two unidentified species with sigmoid conidia. Cluster analysis suggested that zinc concentration and exposure time affected the structure of aquatic hyphomycete assemblages, even though richness had not been severely affected. Both zinc concentration and exposure time significantly affected leaf mass loss, fungal production and sporulation, but not fungal biomass. Zinc exposure reduced leaf mass loss, inhibited fungal production and affected fungal reproduction by either stimulating or inhibiting sporulation rates. The results of this work suggested zinc pollution might depress leaf decomposition in streams due to changes in the structure and activity of aquatic fungi.
The effects of exudates from uncolonized and from partly decayed beech wood on the extension rates of 16 later stage decay fungi were investigated. The partly decayed wood had been colonized by the pyrenomycete Eutypa spinosa, or the basidiomycetes Fomes fomentarius, Stereum hirsutum, and Trametes versicolor, all known as common early decay agents in European beech forests. Sterilized wood pieces were placed onto 0.5% malt agar, opposite to small agar plugs containing the test fungi. The latter showed very variable and species-specific growth responses to the various wood types. The presence of uncolonized wood stimulated extension rates in many species, whereas the four previously decayed wood types had variable stimulatory or inhibitory effects. Wood decayed by S. hirsutum resulted in reduced extension rate, delayed growth, or total inhibition in the majority of species, thus it is suggested that this species uses secondary metabolites in a defensive strategy. A single species was, however, stimulated in the presence of S. hirsutum-decayed wood. In contrast, the presence of wood decayed by F. fomentarius was stimulatory to 45% of the species. The other previously decayed wood types generally resulted in more variable responses, depending upon species. The results are discussed in an ecological context and it is suggested that the exudates from the partly decayed wood that are responsible for the reported effects may function as infochemicals, structuring microbial communities in wood.