Colonization ofRetama raetam seeds by fungi and their significance in seed germination

Examination by scanning electron microscopy and incubation on potato-dextrose agar medium showed that dry seeds ofRetama raetam were externally free of fungi. When planted in sandy loam soil, the seeds become colonized with eleven soil-borne fungal species. The fungi were isolated on cellulose agar, pectin agar and lignin agar media.Aspergillus flavus, A. niger, A. fumigatus, Penicillium capsolatum andFusarium oxysporum had broad occurrence and were recovered on all the three media. The production of hydrolytic enzymes by the isolated fungi depends on the substrate and species.Penicillium capsolatum, P. spinulosum andA. niger had wide enzymatic amplitude and they were able to produce cellulolytic, pectolytic and lignolytic activities on corresponding substrates as well as on seed-coat-containing media. The lignolytic activities of the isolated species exceptChaetomium bostrychodes andTrichoderma viride were enhanced by applying the seed-coat materials as C- source rather than lignin. SoakingR. raetam seeds in culture filtrates of most of the fungi grown on seed-coat-supplemented media induced a pronounced and distinct stimulating effect on seed germination. The most effective filtrates were those ofP. capsolatum, P. spinulosum andSporotrichum pulverulentum.     

Extracellular mannanases and galactanases from selected fungi

Summary Eight thermophilic fungi were tested for production of mannanases and galactanases. Highest mannanase activities were produced byTalaromyces byssochlamydoides andTalaromyces emersonii. Mannanases from all strains tested were induced by locust bean gum except in the case ofThermoascus aurantiacus, where mannose had a greater inducing effect. Locust bean gum was also the best inducer of -mannosidase and galactanase except in the case ofT. emersonii where galactose was a better inducer of both these enzymes. Highest mannanase activity was produced byTalaromyces species when peptone was used as nitrogen source whereas sodium nitrate promoted maximum production of this enzyme byThielavia terrestris andT. aurantiacus. The pH optima of mannanases from the thermophilic fungi were in the range 5.0–6.6 and contrasted with the low pH optimum (3.2) of the enzyme fromAspergillus niger. Galactanases had pH optima in the range 4.3–5.8. The mannanase fromT. emersonii and the galactanase fromT. terrestris were most thermostable, each retaining 100% activity for 3 h at 60°C.     

Cellulose-decomposing fungi of salt marshes in Egypt

Seventy-five species and three varieties which belong to thirty-four genera were identified from 74 soil samples collected from salt marshes in Egypt. The most frequent fungi wereAspergillus fumigatus, Aspergillus niger, Cladosporium herbarum andAlternatia alternata, followed byAspergillus terreus,Curvularia spicifera andPenicillium notatum. Six genera were of moderate occurrence:Penicillium, Futarium, Curvularia, Rhizopus, Stachybotrys, andChaetomium. Five genera were of low occurrence:Paecilomyces, Oephalosporium, Epicoccum, Mucor andMyrothecium.     

Decomposition of organic matter by fungi in saline soils

The object of the present investigation was to study the fungal decomposition of organic matter from different sources, added to the saline soils. The organic matter added was in the form of fresh cuttings of two salt tolerant harbaceous plants namelyDiplachne fusca (Kallar grass) andSesbania aculeata (Dhancha). In addition to these treatments, farm yard manure and press mud (waste of sugar industry) were also used as a source of organic matter. Twelve combinations of these treatments were studied. A number of fungi were isolated from differently treated saline soils incubated at 30 °C. Among the fungi isolatedAspergillus spp. andFusarium solani had the highest frequency of occurrence. The relative cellulolytic ability of 10 fungal species was also estimated.Alternaria humicola andNigrospora sp. were found to be the most cellulolytic among the fungi isolated. The decrease in organic matter due to microbial decomposition was found to be most rapid during first two weeks of incubation. Among the treatments with one organic matter source, press mud produced maximum humus equal to 0.28 %. The pH and electrical conductivity increased slightly due to the closed system where no leaching took place.     

Responses of barley,pea, and maize to inoculation with different vesicular-arbuscular mycorrhizal fungi in irradiated soil

Summary The efficiency of different VAM fungi was investigated by inoculating barley, pea, and maize with different VAM fungi in irradiated soil in pots buried in the field. VAM frequency, growth and nutrient uptake were measured. In barleyGlomus epigaeus (CA) andG. macrocarpus (CA) were the most efficient out of 11 tested species and increased yield of grain by 24% and 21%, though they were not significant according to oneway analysis of variance. In pea, yield of grain was significantly increased from 46% to 104% (mean=68%) by 7 out of 10 tested species and by 105% by application of P fertilizer. The most efficient species wereG. epigaeus (CA),G. mosseae (GB), andG. etunicatus (CA). In maizeG. mosseae (GB) andG. caledonius (DK) increased total yield significantly by 59% and 47% in one experiment and in another experiment yield of cob was increased by 68% byG. mosseae (GB), 72% byG. caledonius (DK), and by 153% by application of P fertilizer. This experiment demonstrated that responsiveness to inoculation by VAM fungi differed among plant species, and that efficiency of different VAM fungi differed.     

Enhancing the mineralization of [U-14C]dibenzo-p-dioxin in three different soils by addition of organic substrate or inoculation with white-rot fungi

The potential for aerobic mineralization of [U-¹⁴C]dibenzo-p-dioxin (DD) was investigated in samples of three different agricultural soils already contaminated with polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) by industrial activities. The influence of amendments, i.e. wheat straw and compost, and of soil treatment by inoculation with lignolytic fungi, grown on wheat straw substrate, was tested. All the soils tested contained an indigenous DD-mineralizing microflora. The soil characterized by the highest organic matter content and the highest content of soil microbial biomass displayed the best DD mineralization of 36.6% within 70 days, compared with the two organic-matter-poor soils with an endogenous DD mineralization of 19.5% and 23.3% respectively. Amendments with compost increased DD mineralization up to 28% in both soils with low organic matter and microbial biomass content, but did not affect mineralization in the organic-matter-rich soil. Addition of wheat straw had no constant influence on DD mineralization in the soils tested. The best DD mineralization resulted from inoculation with lignolytic white-rot fungi (Phanerochaete chrysosporium, Pleurotus sp. Florida, Dichomitus squalens) and with an unidentified lignolytic fungus, which was isolated originally from a long-term PCDD/F-contaminated soil. A mineralization of up to 50% within 70 days was reached by this treatment. The influence of inoculated fungi on mineralization differed between the soils investigated. Received: 14 April 1997 / Received revision: 24 June 1997 / Accepted: 29 June 1997     

Effect of pH and organic matter on the toxicity of heavy metals to growth of some fungi

Increasing the pH from 5 to 9 decreased the toxicity of mercuric chloride, zinc sulfate, lead nitrate, copper sulfate and nickel chloride toward the growth ofAspergillus flavus, Penicillium chrysogenum, Cunninghamella echinulata, Myrothecium verrucaria andPhoma humicola. On the other hand, the toxicity of cadmium chloride was increased by the increasing pH. Also increasing the concentration of organic matter (peptone and yeast extract) from 0.5 to 1.5% induced a significant reduction in the toxicity of all heavy metals toward the growth of all test fungi.     

Associative effect of cellulolytic fungi andAzospirillum lipoferum on yield and nitrogen uptake by wheat

The associative effect of cellulolytic fungi, such asAspergillus awamori andA. niger, with the nitrogen fixer,Azospirillum lipoferum was studied in a soil amended with rice straw. All the inoculants gave significantly higher grain and straw yield and nitrogen uptake by wheat crop than did the uninoculated treatment. The doubling of chemical nitrogen dose significantly increased the yield and nitrogen uptake. It was observed thatA awamori performed significantly better followed byA. niger andA. lipoferum. The maximum benefit was obtained with combined inoculation ofA. awamori andA. lipoferum. Another experiment was conducted in the subsequent year in soil amended with and without rice straw using cellulolytic culture eitherA. awamori orSclerotium rolfsii, andA. lipoferum. Application of straw in soil significantly reduced the yield and N-uptake by wheat crop as compared to the controls. All the inoculants exceptS. rolfsii gave significantly higher grain yield. However, N-uptake by grain was significantly increased only by combined inoculation ofA. lipoferum and either one of the cellulolytic fungi. Similar trends on yield and N-uptake of straw due to inoculants were observed. The maximum benefit was obtained with combined inoculation ofA. awamori andA. lipoferum followed byA. awamori alone on grain yield and only combined inoculants on N-uptake by the crop.     

Ligninolytic properties of different white-rot fungi

Summary Seven white-rot fungi were examined for the production of ligninase, manganese peroxidase and laccase. All these enzymes were found inTrametes gibbosa andTrametes hirsuta. Only manganese peroxidase and laccase were produced byPycnoporus cinnabarinus,Coriolopsis polyzona,Stereum hirsutum,Dichomitus squalens andGanoderma valesiacum. All fungi decolorized Poly B-411 and Indulin AT plates with low-N medium. The differences in enzyme pattern indicate that different species of fungi may employ different modes of lignin metabolism.     

Isolation of keratinolytic fungi from a coal mine dump

During the study of fungal succesion in the coal mine dump in Brzezinka (Poland), soil samples were examined for keratinolytic fungi. These micro-organisms were rather poorly represented in the area studied. Out of 300 soil samples examined, only 48 (16%) were positive for keratinolytic fungi.Trichophyton ajelloi andArthroderma curreyi were the prevailing species. These species occurred practically at two locations, i.e. on the naked carbon rocks inhabited by algae crops (chiefly byCyanophyta) and in the pine litter. It can be supposed that the occurrence of keratinolytic fungi was more dependent on the favourable general conditions such as increasing organic matter content, microflora, and humidity than on the presence of keratin remains in the soil. Because of the lack of potentially pathogenic fungi, the coal mine dump examined cannot be considered as an important source of fungal infection.     

Degradation and oligomerization of syringic acid by distinctive ecological groups of fungi

Forty-four terrestrial and aeroaquatic and aquatic fungi, including fifteen species causing white-rot, four species causing brown-rot, and some species causing soft-rot of wood, were tested for their ability to degrade the monomer syringic acid, which is released during decay of angiosperm lignin. None of the white- or brown-rot species caused any detectable degradation of syringic acid under the test conditions; however, six typical white-rot fungi strongly oligomerized syringic acid, both with and without cosubstrate. The main polymerization product was identified as a 1,3-dimethylpyrogallol oligomer by¹³C-NMR. Other minor metabolic products were methylated and hydroxylated derivatives. Oligomerization depended on the presence of 1 or 2 methoxy groups in ortho position to the hydroxy group of the substrate. Among the remaining fungi,Exophiala jeanselmei, Fusarium eumartii, andPaecilomyces variotii completely and rapidly degraded syringic acid (5 g/liter) within 48 to 100 hours. A further seven species were able to degrade syringic acid to some extent when glucose was added. Methylated and demethylated metabolic intermediates were identified by GC/MS.     

Field response of wheat to arbuscular mycorrhizal fungi and drought stress

Mycorrhizal plants often have greater tolerance to drought than nonmycorrhizal plants. This study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi inoculation on growth, grain yield and mineral acquisition of two winter wheat (Triticum aestivum L.) cultivars grown in the field under well-watered and water-stressed conditions. Wheat seeds were planted in furrows after treatment with or without the AM fungi Glomus mosseae or G. etunicatum. Roots were sampled at four growth stages (leaf, tillering, heading and grain-filling) to quantify AM fungi. There was negligible AM fungi colonization during winter months following seeding (leaf sampling in February), when soil temperature was low. During the spring, AM fungi colonization increased gradually. Mycorrhizal colonization was higher in well-watered plants colonized with AM fungi isolates than water-stressed plants. Plants inoculated with G. etunicatum generally had higher colonization than plants colonized with G. mosseae under both soil moisture conditions. Biomass and grain yields were higher in mycorrhizal than nonmycorrhizal plots irrespective of soil moisture, and G. etunicatum inoculated plants generally had higher biomass and grain yields than those colonized by G. mosseae under either soil moisture condition. The mycorrhizal plants had higher shoot P and Fe concentrations than nonmycorrhizal plants at all samplings regardless of soil moisture conditions. The improved growth, yield and nutrient uptake in wheat plants reported here demonstrate the potential of mycorrhizal inoculation to reduce the effects of drought stress on wheat grown under field conditions in semiarid areas of the world.     

Biodegradation of pentachlorophenol by white rot fungi under ligninolytic and nonligninolytic conditions

The roles of lignin peroxidase, manganese peroxidase, and laccase were investigated in the biodegradation of pentachlorophenol (PCP) by several white rot fungi. The disappearance of pentachlorophenol from cultures of wild type strains,P. chrysosporium, Trametes sp. andPleurotus sp., was observed. The activities of manganese peroxidase and laccase were detected inTiametes sp. andPleurotus sp. cultures. However, the activities of ligninolytic enzymes were not detected inP. chrysosporium cultures. Therefore, our results showed that PCP was degraded under ligninolytic as well as nonligninolytic conditions. Indicating that lignin peroxidase, manganese peroxidase, and laccase are not essential in the biodegradation of PCP by white rot fungi.     

Effect of Wood Modification on Lignin Consumption and Synthesis of Lignolytic Enzymes by the Fungus Panus (Lentinus) tigrinus

Lignin consumption and synthesis of lignolytic enzymes by the fungus Panus (Lentinus) tigrinuscultivated on solid phase (modified and unmodified birch and pine sawdusts) were studied. The fungus grew better on and consumed more readily the birch lignin than the pine wood. Peroxidase activity was higher in the case of pine sawdust; laccase and lignolytic activities, in the case of birth sawdust. Treatment with ammonia or sulfuric acid decreased lignin consumption by this fungus cultivated on either medium. Modification of sawdust by ultrasound increased lignin consumption and may be recommended for accelerating biodegradation of lignocellulose substrates.     

Keratinophilic fungi from soil of Brittany,France

The Present work reports the study of the distribution of keratinophilic fungi isolated from 39 samples of soil collected in Brittany, France. Keratinophilic fungi were isolated from 35 (92.3%) of the samples studied. The most frequently found species wereFusarium moniliforme, Penicillium viridicatum and an unidentified species ofAcremonium. The other fungi isolated were members of the generaChrysosporium, Gliocladium, Mucor, Trichoderma andTrichophyton.     

Some characteristics of ammonia fungi 1. In relation to their ligninolytic enzyme activities

Twenty-six species of ammonia fungi comprising 71 strains were screened for ligninolytic activity using agar plate tests. The tests comprised a wood powder plate test, the Bavendamm reactions, and a Remazol Brilliant blue R (RBBR) decolorization test. The wood powder plate test detected phenol oxidases of Coprinus spp., whereas this method obviously detected no activities from facultative mycorrhizal fungi, such as Hebeloma radicosoides and ectomycorrhiza: H. spoliatum and H. vinosophyllum. With quantitative assays of ligninolytic activity, Coprinus phlyctidosporus, C. echinosporus, Lyophyllum tylicolor, Lepista nuda, L. tarda, Calocybe leucocephala, and Crucispora rhombisperma, which grow on oak-leaf litter, the major phenol-oxidizing enzyme was a laccase. The concentration of urea affected laccase activity; however, urea was not the obligate nitrogen source for the laccase production.     

Variation in aluminum resistance among arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi mediate interactions between plants and soils, and are important where nutrient or metal concentrations limit plant growth. Variation in fungal response to edaphic conditions may influence the effectiveness of the plant-mycorrhizal association in some soil environments. Andropogon virginicus (broomsedge) colonizes disturbed sites in the eastern United States, including acidic mine soils where aluminum (Al) is phytotoxic, and Al resistance in broomsedge has been associated with colonization by the AM fungus Glomus clarum. In the present study, inter- and intra-specific variation to confer Al resistance to broomsedge was assessed among selected species of AM fungi. Broomsedge seeds were grown in sand culture inoculated with one of five isolates of three species of fungi (G. clarum, Acaulospora morrowiae, and Scutellospora heterogama). Plants were exposed to 0 or 400 µM Al in nutrient solution and harvested after 4 or 9 weeks of growth. Mean infection percentage, plant biomass, and plant tissue Al and phosphorus (P) concentrations were measured. G. clarum conferred the greatest Al resistance to broomsedge, with the lowest variability among isolates for colonization and growth inhibition by Al [tolerance indices (TI) between 22.4 and 92.7%]. Broomsedge plants colonized by A. morrowiae were consistently the most sensitive to Al, with little variation among isolates (TI between 1.6 and 12.1%). Al resistance by S. heterogama isolates was intermediate and wide-ranging (TI between 3.9 and 40.0%). Across all AM fungal isolates, resistance was associated with high rates of colonization and low tissue Al concentrations of broomsedge plants. The functional diversity in Al resistance displayed by these AM fungi reflect variation in acclimation mechanisms operating in the mycorrhizal symbiosis under environmental stress.     

Lignin degradation andIn vitro digestibility of wheat straw treated with Brazilian tropical species of white rot fungi

Brazilian tropical fungi were screened for lignin degradation, and the ability to increase or decrease thein vitro digestibility and pH of wheat straw used as a substrate (at 25 and 30 °C after 30 and 60 d of incubation). Out of 72 species and strains ofAgrocybe, Antrodiella, Auricularia, Coriolopsis, Cymatoderma, Fomitopsis, Ganoderma, Gerronema, Gloeophyllum, Gymnopilus, Irpex, Lentinus, Melanoporia, Oligoporus, Oudemansiella, Panaeolus, Peniophora, Phellinus, Pherotus, Psathyrella, Psilocybe, Pycnoporus, Rigidoporus, Schizophyllum, Trametes, Trichaptum andTyromyces, 22 decomposed more than 50% of lignin and 10 increased thein vitro substrate digestibility by more than 30 U. The highest degradation of lignin was observed withLentinus crinitus (80 %, 60 d) and the highest increase inin vitro substrate digestibility was caused byPeniophora utriculosa (36 U, 30 d).     

Interrelationship betweenCoprinus lagopus andFusarium udum in soil in relation to competitive saprophytic ability and microbial antagonism

Summary The interrelationship between the growth ofCoprinus lagopus andFusarium udum on pigeon pea substrates in soil was studied at 22-2°C and 30±2°C in relation to their competitive saprophytic ability and antagonism.C. lagopus was observed to be a potent and frequent colonizer of pigeon pea substrates in soil along withF. udum. Saprophytic colonization of pigeon pea substrate byF. udum precolonized byC. lagopus was inhibited in all inoculum soil mixtures. Saprophytic colonization of the substrate byF. udum was better at 22°C than at 30°C and that byC. lagopus better at 30°C than at 22°C. The colonization of substrate by each fungus was suppressed by the other fungus depending upon the temperature used. Hyphal parasitism and colony interactions between these fungi and also with a number of other saprophytic fungi were investigated. No antagonistic reaction was observed betweenF. udum andC. lagopus. However, these fungi were observed to be potent antagonists against other microfungi tested. The formation of fruiting bodies ofC. lagopus was also observed in the laboratory on nutrient media but more frequently on pigeon pea substrates.     

Studies on the methylation of mercuric chloride by pure cultures of bacteria and fungi

Small amounts of methylmercury were produced during 7 days aerobic growth in the presence of sublethal amounts of mercuric chloride by the following bacterial species studied:Pseudomonas fluorescens, Mycobacterium phlei, Escherichia coli, Aerobacter aerogenes, Bacillus megaterium. Under the same conditions methylmercury was also formed by mycelium of the fungi investigated:Aspergillus niger, Scopulariopsis brevicaulis andSaccharomyces cerevisiae. The concentration of the methylmercury produced by the various organisms did not vary much and was of the same order of magnitude as that found in Swedish experiments with lake sediments. In bacteria most of the methylmercury formed was present in the culture liquid, whereas the remainder was in or on the cells. In contrast, methylmercury formed by fungi was for the greater part present in the mycelium. The production of methylmercury byE. coli andA. aerogenes was lower under anaerobic conditions than under aerobic conditions.