The structure of micromycete communities and their synecologic interactions with basidiomycetes during decomposition of plant debris

We investigated the interactions between micromycetes and basidiomycete mycelium on plant substrates in the course of their 3-year incubation in the litter of ecologically intact spruce forests of the Central State Biosphere Forest Sanctuary (Nelidovo District, Tver oblast). Only 40-60% of the micromycetes were involved in direct antagonistic interactions with basidiomycetous fungi. In terms of the ratio between physiologically active strains and those which did not interact with basidiomycete mycelium, we revealed differences in the structure of micromycete communities developing on various types of substrates (xylem, bark, sphagnum, leaves, needles, litter, and cotton grass). The micromycetes tested belonged to 49 species. At the end of the observation period, the fraction of microscopic fungi that actively influenced basidiomycete mycelium was four times lower in the inactive litter fraction (lignin-containing xylem debris) than in the active fraction (grass substrates). The mechanisms of indirect regulation of the structure and functions of micromycete communities are discussed, which may be based on the accumulation of phenolic compounds in the medium and changes in the enzyme activities of basidiomycete mycelium.     

Simulated nitrogen deposition affects wood decomposition by cord-forming fungi

Anthropogenic nitrogen (N) deposition affects many natural processes, including forest litter decomposition. Saprotrophic fungi are the only organisms capable of completely decomposing lignocellulosic (woody) litter in temperate ecosystems, and therefore the responses of fungi to N deposition are critical in understanding the effects of global change on the forest carbon cycle. Plant litter decomposition under elevated N has been intensively studied, with varying results. The complexity of forest floor biota and variability in litter quality have obscured N-elevation effects on decomposers. Field experiments often utilize standardized substrates and N-levels, but few studies have controlled the decay organisms. Decomposition of beech (Fagus sylvatica) blocks inoculated with two cord-forming basidiomycete fungi, Hypholoma fasciculare and Phanerochaete velutina, was compared experimentally under realistic levels of simulated N deposition at Wytham Wood, Oxfordshire, UK. Mass loss was greater with P. velutina than with H. fasciculare, and with N treatment than in the control. Decomposition was accompanied by growth of the fungal mycelium and increasing N concentration in the remaining wood. We attribute the N effect on wood decay to the response of cord-forming wood decay fungi to N availability. Previous studies demonstrated the capacity of these fungi to scavenge and import N to decaying wood via a translocating network of mycelium. This study shows that small increases in N availability can increase wood decomposition by these organisms. Dead wood is an important carbon store and habitat. The responses of wood decomposers to anthropogenic N deposition should be considered in models of forest carbon dynamics.     

Survival of Micromycetes and Actinobacteria under Conditions of Long-Term Natural Cryopreservation

Almost all of the investigated samples of the Arctic and Antarctic permafrost sediments of different genesis with ages from 5–10 thousand to 2–3 million years were found to contain viable micromycete and bacterial cells. The maximum amounts of viable cells of fungi (up to 10⁴CFU/g air-dried sample) and bacteria (up to 10⁷–10⁹CFU/g air-dried sample) were present in fine peaty sediment samples taken from different depths. The identified micromycetes belonged to more than 20 genera of the divisions Basidiomycota, Ascomycota, and Zygomycota, and some represented mitosporic fungi. Thawing the samples at 35 and 52°C allowed the number of detected fungal genera to be increased by more than 30%. Aerobic heterotrophic prokaryotes were dominated by coryneform, nocardioform, and spore-forming microorganisms of the order Actinomycetales.Analysis of the isolated fungi and actinomycetes showed that most of them originated from the microbial communities of ancient terrestrial biocenoses.     

A comparison of dinitrogen fixation rates in wood litter decayed by white-rot and brown-rot fungi

Nitrogen fixation rates, as estimated by the acetylene reduction technique, were determined in conifer wood litter being decayed by brown- and white-rot fungi. Average ethylene production rates were significantly higher in white-rotted wood (15.1 nmol g^–1 day^–1) than in brown-rotted wood (2.3 nmol g^–1 day^–1). This difference may be related to a higher soluble sugar content in white-versus brown-rotted wood. The nitrogen-fixing bacteriumAzospirillum was not detected in any of the decaying wood samples examined. Greater nitrogen additions from nitrogen-fixing bacteria may be a factor in the more rapid white-rot decay of hardwood litter, as compared to the slower brown-rot decay of conifer wood.     

Enzyme Immunoassay of Herbicide Decomposition by Soil and Wood Decay Fungi

The effect of herbicide atrazine was studied on the growth and development of a number of soil and wood decay fungi: white-rot basidiomycetes (Cerrena maxima, Coriolopsis fulvocenerea, and Coriolus hirsutus), thermophilic micromycetes from self-heating grass composts (cellulolytic fungus Penicilliumsp. 13 and noncellulolytic ones Humicola lanuginosaspp. 5 and 12), and mesophilic phenol oxidase-producing micromycete Mycelia sterilia INBI 2-26. Detection of atrazine in liquid fungal cultures was performed by using the enzyme immune assay technique. Both stimulation (Humicola lanuginosa 5) and suppression (Humicola lanuginosa 12 and Penicillium sp. 13) of fungal growth with atrazine were observed on solid agar media. HyphomyceteMycelia sterilia INBI 2-26 was almost insensitive to the presence of atrazine. Neither of the thermophilic strains was capable of atrazine consumption in three-week cultivation. In contrast with that, active laccase producers Cerrena maxima, Coriolopsis fulvocenerea, and Coriolus hirsutus consumed up to 50% atrazine in 5-day cultivation in the presence of the xenobiotic and at least 80–92% in 40 days. Mycelia steriliaINBI 2-26, which also forms extracellular laccase, also consumed up to 70% atrazine in 17 days. The degree of atrazine consumption depended on the term of its addition to the fungal culture medium.     

Effect of Oil on the Population,Biomass, and Viability of Fungi in Highmoor Peats

Some microbiological parameters, such as the fungal mycelium length, the number of fungal spores, the distribution profiles of micromycetes, the viability of fungal propagules, the length distribution of micromycete hyphae, and the ratio between fungal spores and yeastlike cells, can be used to determine the degree of soil contamination with oil and the concentration that is inhibitory to micromycete complexes of highmoor peats.     

Mites as Selective Fungal Carriers in Stored Grain Habitats

Mites are well documented as vectors of micromycetes in stored products. Since their vectoring capacity is low due to their small size, they can be serious vectors only where there is selective transfer of a high load of specific fungal species. Therefore the aim of our work was to find out whether the transfer of fungi is selective. Four kinds of stored seeds (wheat, poppy, lettuce, mustard) infested by storage mites were subjected to mycological analysis. We compared the spectrum of micromycete species isolated from different species of mites (Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, Caloglyphus rhizoglyphoides and Cheyletus malaccensis) and various kinds of stored seeds. Fungi were separately isolated from (a) the surface of mites, (b) the mites' digestive tract (= faeces), and (c) stored seeds and were then cultivated and determined. The fungal transport via mites is selective. This conclusion is supported by (i) lower numbers of isolated fungal species from mites than from seeds; (ii) lower Shannon–Weaver diversity index in the fungal communities isolated from mites than from seeds; (iii) significant effect of mites/seeds as environmental variables on fungal presence in a redundancy analysis (RDA); (iv) differences in composition of isolated fungi between mite species shown by RDA. The results of our work support the hypothesis that mite–fungal interactions are dependent on mite species. The fungi attractive to mites seem to be dispersed more than others. The selectivity of fungal transport via mites enhances their pest importance.     

Application of Bacillus-antagonists for biocontrol of fungi degrading raw wood

Species composition of micromycete complexes colonizing aspen, birch, and pine wood was studied. Calculation of the Sorens-Tchekanovsky similarity coefficients showed that these complexes shared a high degree of similarity. They were dominated by the representatives of the genera Penicillium, Paecilomyces, Trichoderma, and Rhizopus. Some antagonistic bacilli inhibited growth and development of wood-decay fungi in vitro and led to the formation of spheroplasts on growing hyphae. A study of possible involvement of bacillary mycolytic enzymes in the inhibition of wood-decay fungi demonstrated selectivity of their lytic effect, which was determined by the genus and species of micromycetes and did not correlate with their relative resistance to antagonists.     

Use of antagonistic bacilli for biocontrol of fungi degrading fresh wood

The species composition of micromycete complexes colonizing aspen, birch, and pine wood was studied. Calculation of the Sorens-Tchekanovsky similarity coefficients showed that these complexes shared a high degree of similarity. They were dominated by representatives of the genera Penicillium, Paecilomyces, Trichoderma, and Rhizopus. Some antagonistic bacilli inhibited growth and development of wood-decay fungi in vitro and led to the formation of spheroplasts on growing hyphae. A study of possible involvement of bacillary mycolytic enzymes in the inhibition of wood-decay fungi demonstrated selectivity of their lytic effect, which was determined by the genus and species of micromycetes and did not correlate with their relative resistance to antagonists.     

Biosynthesis of Hydrolytic Enzymes during Cocultivation of Macro- and Micromycetes

Effects of cocultivation of higher basidiomycetes and zygomycetes on biosynthesis of cellulases, amylases, and proteases were studied. Four optimal pairs of cultures of fungi were selected. Of these, three pairs belonged to higher fungi and one pair was constituted by fungi of distinct ecological groups, a macromycete and a micromycete. The activities of amylase and protease were 1.5–2 times higher and the activity of cellulase was lower during the growth of associations of higher fungi. The mixed association of the macromycete Schizophyllum commune and the micromycete Mucor sp. was the most active producer of hydrolytic enzymes. During the growth of this mixed association, increases of 4 and 1.5 times were observed in the activity of endoglucanase and protease, respectively, paralleled by stimulation of amylase formation.     

The Structure of the Micromycete Complexes of Oligotrophic Peat Deposits in the Southern Taiga Subzone of West Siberia

The analysis of the micromycete complexes of oligotrophic peat deposits in the Vasyugan Marsh by direct count and culture methods showed that micromycete carbon comprises no more than 3% of the total peat carbon and that the microscopic fungal biomass varies from 2 to 13 tons/hectare, depending on the season and the peat deposit thickness. Fungal spores were found in all layers of the peat deposits, whereas the mycelium was found only in the active peat layer. The high abundance of eukaryotic cells in the peats was due to the presence of yeastlike cells rather than fungal spores. Analyses by culture methods showed that micromycetes were present in all peat layers and that their abundance tended to decrease with depth, except for yeasts, which were uniformly distributed in a vertical direction. The micromycete complexes of the peat deposits were similar in their diversity and abundance of dominant species but differed in the composition of minor species. Peat yeasts were dominated by ascomycetes.     

The structure of the micromycete complexes of oligotrophic peat deposits in the southern taiga subzone of West Siberia

The analysis of the micromycete complexes of oligotrophic peat deposits in the Vasyugan Marsh by direct count and culture methods showed that the micromycete carbon comprises no more than 3% of the total peat carbon and that the microscopic fungal biomass varies from 2 to 13 tons/hectare, depending on the season and the peat deposit thickness. Fungal spores were found in all layers of the peat deposits, whereas the mycelium was found only in the active peat layer. The high abundance of eukaryotic cells in the peats was due to the presence of yeastlike cells rather than fungal spores. Analyses by culture methods showed that micromycetes were present in all peat layers and that their abundance tended to decrease with depth, except for yeasts, which were uniformly distributed in a vertical direction. The micromycete complexes of the peat deposits were similar in the diversity and abundance of dominant species but differed in the composition of minor species. Peat yeasts were dominated by ascomycetes.     

Immunoenzyme analysis of decomposition of herbicides by soil and wood-rot fungi

The effect of herbicide atrazine was studied on the growth and development of a number of soil and wood decay fungi: white-rot basidiomycetes (Cerrena maxima, Coriolopsis fulvocenerea, and Coriolus hirsutus), thermophilic micromycetes from self-heating grass composts (cellulolytic fungus Penicillium sp. 13 and noncellulolytic ones Humicola lanuginosa spp. 5 and 12), and mesophilic phenol oxidase-producing micromycete Mycelia sterilia INBI 2-26. Detection of atrazine in liquid fungal cultures was performed by using enzyme immunoassay technique. Both stimulation (Humicola lanuginosa 5) and suppression (Humicola lanuginosa 12 and Penicillium sp. 13) of fungal growth with atrazine were observed on solid agar media. Hyphomycete Mycelia sterilia INBI 2-26 was almost insensitive to the presence of atrazine. Neither of thermophilic strains was capable of atrazine consumption in three-week cultivation. In contrast with that, active laccase producers Cerrena maxima, Coriolopsis fulvocenerea, and Coriolus hirsutus consumed up to 50% atrazine in 5-day cultivation in the presence of the xenobiotic and at least 80-90% in 40 days. Mycelia sterilia INBI 2-26, which also forms extracellular laccase, also consumed up to 70% atrazine in 17 days. The degree of atrazine consumption depended on the term of its addition to the fungal culture medium.     

Contrasting Effects of Elevated Temperature and Invertebrate Grazing Regulate Multispecies Interactions between Decomposer Fungi

Predicting the influence of biotic and abiotic factors on species interactions and ecosystem processes is among the primary aims of community ecologists. The composition of saprotrophic fungal communities is a consequence of competitive mycelial interactions, and a major determinant of woodland decomposition and nutrient cycling rates. Elevation of atmospheric temperature is predicted to drive changes in fungal community development. Top-down regulation of mycelial growth is an important determinant of, and moderator of temperature-driven changes to, two-species interaction outcomes. This study explores the interactive effects of a 4 °C temperature increase and soil invertebrate (collembola or woodlice) grazing on multispecies interactions between cord-forming basidiomycete fungi emerging from colonised beech (Fagus sylvatica) wood blocks. The fungal dominance hierarchy at ambient temperature (16 °C; Phanerochaete velutina > Resinicium bicolor > Hypholoma fasciculare) was altered by elevated temperature (20 °C; R. bicolor > P. velutina > H. fasciculare) in ungrazed systems. Warming promoted the competitive ability of the fungal species (R. bicolor) that was preferentially grazed by all invertebrate species. As a consequence, grazing prevented the effect of temperature on fungal community development and maintained a multispecies assemblage. Decomposition of fungal-colonised wood was stimulated by warming, with implications for increased CO₂ efflux from woodland soil. Analogous to aboveground plant communities, increasing complexity of biotic and abiotic interactions appears to be important in buffering climate change effects on soil decomposers.     

Comparison of Fungal Activities on Wood and Leaf Litter in Unaltered and Nutrient-Enriched Headwater Streams

Fungi are the dominant organisms decomposing leaf litter in streams and mediating energy transfer to other trophic levels. However, less is known about their role in decomposing submerged wood. This study provides the first estimates of fungal production on wood and compares the importance of fungi in the decomposition of submerged wood versus that of leaves at the ecosystem scale. We determined fungal biomass (ergosterol) and activity associated with randomly collected small wood (<40 mm diameter) and leaves in two southern Appalachian streams (reference and nutrient enriched) over an annual cycle. Fungal production (from rates of radiolabeled acetate incorporation into ergosterol) and microbial respiration on wood (per gram of detrital C) were about an order of magnitude lower than those on leaves. Microbial activity (per gram of C) was significantly higher in the nutrient-enriched stream. Despite a standing crop of wood two to three times higher than that of leaves in both streams, fungal production on an areal basis was lower on wood than on leaves (4.3 and 15.8 g C m⁻² year⁻¹ in the reference stream; 5.5 and 33.1 g C m⁻² year⁻¹ in the enriched stream). However, since the annual input of wood was five times lower than that of leaves, the proportion of organic matter input directly assimilated by fungi was comparable for these substrates (15.4 [wood] and 11.3% [leaves] in the reference stream; 20.0 [wood] and 20.2% [leaves] in the enriched stream). Despite a significantly lower fungal activity on wood than on leaves (per gram of detrital C), fungi can be equally important in processing both leaves and wood in streams.     

Behavioral ecology and natural history of Blepharidatta brasiliensis (Formicidae, Blepharidattini)

Fungus-growing ants (Attini, Formicidae) originated about 45–65 million years ago when forging a mutualistic association with basidiomycete fungi (Lepiotaceae). Here we use information on the biology of the non-leafcutting fungus-growing ants and their close relatives in the genus Blepharidatta to evaluate hypotheses for the evolutionary origin of fungus-growing behavior in attine ants. Observations on the natural history, ecology, and behavior of the Amazonian species Blepharidatta brasiliensis are reported here for the first time. Like most attine species, B. brasiliensis and the great majority of species in the tribe Blepharidattini are inhabitants of moist tropical rainforest, suggesting a rainforest habitat also for the ancestral attine ant. The ancestral attine was probably a leaf litter dweller, building small to medium sized nests (e.g., 20–200 workers) either between leaves in the litter or in decaying wood on the rainforest floor. Received 20 December 2005; revised 1 March 2006; accepted 7 March 2006.     

Dry matter and nutrient inputs through litter fall in a dry tropical forest of India

The present paper elucidates the pattern of leaf and non-leaf fall and quantifies of the total annual input of litter in a dry tropical forest of India. In addition, concentration of selected nutrients in various litter species and their annual return to the forest floor are examined. Total annual input of litter measured in litter traps ranged between 488.0–671.0 g m^-2 of which 65–72% was leaf litter fall and 28–35% wood litter fall. 73–81% leaves fall during the winter season. Herbaceous litter fall ranged between 80.0–110.0 g m^-2 yr^-1. The annual nutrient return through litter fall amounted (kg ha^-1): 51.6–69.6 N, 3.1–4.3 P, 31.0–40.0 Ca, 14.0–19.0 K and 3.7–5.0 Na, of which 71–77% and 23–29% were contributed by leaf and wood litter fall, respectively for different nutrients. Input of nutrients through herbaceous litter was: 13.0–16.6 for N, 1.0–1.4 for P, 4.0–5.0 for Ca, 7.9–10.5 for K and 0.8–1.0 kg ha^-1 yr^-1 for Na.     

Respiration from coarse wood litter in central Amazon forests

Respiration from coarse litter (trunks and large branches >10 cm diameter) was studied in central Amazon forests. Respiration ratesvaried over almost two orders of magnitude (1.003–0.014 µg Cg^–1 C min^–1, n = 61), and weresignificantly correlated with wood density (r² _adj= 0.42), and moisture content (r² _adj= 0.39). Additional samples taken from a nearby pasture indicatedthat wood moisture content was the most important factor controllingrespiration rates across sites (r² _adj =0.65). Based on average coarse litter wood density and moisture content,the mean long-term carbon loss rate due to respiration was estimated tobe 0.13 yr^–1 (range of 95% prediction interval(PI) = 0.11–0.15 yr^–1). Comparing meanrespiration rate with mean mass loss (decomposition) rate from aprevious study, respiratory emissions to the atmosphere from coarselitter were predicted to be 76% (95% PI =65–88%) of total carbon loss, or about 1.9 (95% PI= 1.6–2.2) Mg C ha^–1yr^–1. Optimum respiration activity corresponded toabout 2.5 g H₂O g^–1 dry wood, and severelyrestricted respiration to < 0.5 g H₂O g^–1dry wood. Respiration from coarse litter in central Amazon forests iscomparable in magnitude to decomposing fine surface litter (e.g. leaves,twigs) and is an important carbon cycling component when characterizingheterotrophic respiration budgets and net ecosystem exchange(NEE).     

Micromycetes and actinobacteria under conditions of many years of natural cryopreservation]

Almost all of the investigated samples of the Arctic and Antarctic permafrost sediments of different genesis with ages from 5-10 thousand to 2-3 million years were found to contain viable micromycete and bacterial cells. The maximum amounts of viable cells of fungi (up to 10(4) CFU/g air-dried sample) and bacteria (up to 10(7)-10(9) CFU/g air-dried sample) were present in fine peaty sediment samples taken from different depths. The identified micromycetes belonged to more than 20 genera of the divisions Basidiomycota, Ascomycota, and Zygomycota, and some represented mitosporic fungi. Thawing the samples at 35 and 52 degrees C allowed the number of detected fungal genera to be increased by more than 30%. Aerobic heterotrophic prokaryotes were dominated by coryneform, nocardioform, and spore-forming microorganisms of the order Actinomycetales. Analysis of the isolated fungi and actinomycetes showed that most of them originated from the microbial communities of ancient terrestrial biocenoses.     

Biodelignification of Lemon Grass and Citronella Bagasse by White-Rot Fungi

Twelve white-rot fungi were grown in solid-state culture on lemon grass (Cymbopogon citratus) and citronella (Cymbopogon winterianus) bagasse. The two lignocellulosic substrates had 11% permanganate lignin and a holocellulose fraction of 58%. After 5 to 6 weeks at 20°C, nine fungi produced a solid residue from lemon grass with a higher in vitro dry matter enzyme digestibility than the original bagasse; seven did the same for citronella. The best fungus for both substrates was Bondarzewia berkeleyi; it increased the in vitro dry matter enzyme digestibility to 22 and 24% for lemon grass and citronella, respectively. The increases were correlated with weight loss and lignin loss. All fungi decreased lignin contents: 36% of the original value for lemon grass and 28% for citronella. Practically all fungi showed a preference for hemicellulose over cellulose.