Succession of microfungal assemblages in decomposing peatland plants

We investigated the microfungal assemblages in the decomposing tissues of dominant plant species in two peatlands in southern boreal Alberta, Canada, to determine if distinct patterns of succession of microfungi occurred throughout the first two years of decomposition. These plant species were Sphagnum fuscum from a bog and Carex aquatilis leaves and rhizomes and Salix planifolia leaves and roots from a riverine, sedge-dominated fen. Canonical correspondence analyses, a multivariate statistical analysis used infrequently in mycological research, revealed distinct patterns of fungal species succession in two of the five litters (S. fuscum and C. aquatilis leaves). Furthermore, our analyses showed that substantially different microfungal assemblages were associated with these litters within the first two years of decomposition. Litter quality variables, such as total nitrogen, total phosphorus, and total carbon tissue nutrient concentrations, explained most of the succession patterns and differences in the microfungal assemblages of these five litters. Our data did not reveal the classical taxonomic zygomycete – ascomycete/fungi imperfecti – basidiomycete pattern of succession during organic matter decomposition. Similarly, a succession of functional groups of microfungi, i.e., cellulose-degraders preceding lignin-degraders, generally was not apparent. Instead, microfungi with broad spectra of enzymatic abilities co-existed over the first two years of decomposition in these peatland plant litters. These microfungi have a limited ability to decompose complex phenolic polymers, such as lignin, resulting in the accumulation of peat in these ecosystems. Some microfungal taxa were not affected by changes in litter quality, environmental variables, or surface water chemistry and were present at all stages of decomposition.     

Vertical Divergence of Cultured Microfungal Communities Through the Depth in Different Soil Formations at Nahal Nizzana,Western Negev Desert,Israel

We examined the depth-wise distribution of microfungi through 0–50-cm crusted sandy and playa profiles at the Nizzana research site, the Negev desert, Israel. A total of 188 species from 77 genera was isolated using the soil dilution plate method. Density of microfungal isolates sharply decreased with depth highly positively correlating with organic matter content at the sandy profiles. High load of solar radiation (at the surface) as well as strongly limited aeration, water infiltration, and increased salinity (at the playa depth) led to dominance of melanin-containing species with large, multicellular conidia both in the topsoil of all profiles and in the deep playa layers, while at 1–30 cm, species producing light-colored small one-celled conidia mostly prevailed. In that way, the above vertical variations resemble differences in the composition of topsoil microfungal communities found between the sites located in the Negev desert and in the Mediterranean region of Israel.     

Microfungal diversity associated with Kindbergia oregana in successional forests of British Columbia

Species richness and species composition of microfungi associated with Oregon beaked moss (Kindbergia oregana) were studied at two forest chronosequences on southeast Vancouver Island, British Columbia, Canada. The purposes were to investigate the effects of clear-cutting and the transformation of old-growth forests into secondary forests on microfungi and the succession of microfungi in relation to long-term stand development. Green and brown parts of moss were collected from the forest floor of Douglas-fir (Pseudotsuga menziesii) stands of four age classes: post-harvest regeneration (13–14 years), immature (50–51 years), and mature (85–101 years) stands, and a control old-growth (296–324 years) stand, and used for the isolation of microfungi. A total of 49 microfungal species were recorded. Study site, stand age, and moss parts significantly affected the species richness and species composition of microfungi. The species richness of microfungi was significantly greater on brown than on green moss parts and lower in post-harvest regenerations than in forest stands of the other age classes. The species composition of major microfungal species changed gradually along the seral stages. Possible environmental and biological factors that could account for the succession of microfungi were discussed.     

An association-analysis of montane grasslands of Sri Lanka

Association-analyses were made of montane grasslands (patanas) of Sri Lanka using higher plant and soil microfungal data. Stand classifications derived from higher plants and microfungi were remarkably parallel and were in complete agreement with the tentative division of patanas into five major types. The ecological distinctiveness of the five patanas was further evident from the phytosociological affinities of species indicated by classifications of higher plants and microfungi. Multivariate analyses of higher plants and fungi from the same ecosystem are regarded as alternative approaches which provide more information together than alone.     

Microfungal “Weeds” in the Leafcutter Ant Symbiosis

Leafcutter ants (Formicidae: tribe Attini) are well-known insects that cultivate basidiomycete fungi (Agaricales: Lepiotaceae) as their principal food. Fungus gardens are monocultures of a single cultivar strain, but they also harbor a diverse assemblage of additional microbes with largely unknown roles in the symbiosis. Cultivar-attacking microfungi in the genus Escovopsis are specialized parasites found only in association with attine gardens. Evolutionary theory predicts that the low genetic diversity in monocultures should render ant gardens susceptible to a wide range of diseases, and additional parasites with roles similar to that of Escovopsis are expected to exist. We profiled the diversity of cultivable microfungi found in 37 nests from ten Acromyrmex species from Southern Brazil and compared this diversity to published surveys. Our study revealed a total of 85 microfungal strains. Fusarium oxysporum and Escovopsis were the predominant species in the surveyed gardens, infecting 40.5% and 27% of the nests, respectively. No specific relationship existed regarding microfungal species and ant-host species, ant substrate preference (dicot versus grass) or nesting habit. Molecular data indicated high genetic diversity among Escovopsis isolates. In contrast to the garden parasite, F. oxysporum strains are not specific parasites of the cultivated fungus because strains isolated from attine gardens have similar counterparts found in the environment. Overall, the survey indicates that saprophytic microfungi are prevalent in South American leafcutter ants. We discuss the antagonistic potential of these microorganisms as “weeds” in the ant–fungus symbiosis.     

Microfunghi del suolo di aree floristicamente omogenee di tre cenosi boschive delle Prealpi bellunesi

Abstract

Soil microfungi in homogeneous areas of three plant communities of North Italy.—The soil microfungi associated with three different community types in Prealpine region of North Italy were investigated. Frequency values for the taxonomic entities isolated were calculated, based on occurrence at sampling sites, in each community. Most of the entities were quantitatively rare. The microfungal communities associated with Acer pseudoplatanus and Fraxinus excelsior, with Ostrya carpinifolia and with Fagus sylvatica appeared to be a distinctive group, even if many of them contained a substantial number of species wich are common with other vegetation types.     

Cultivable microscopic fungi from an underground chemosynthesis-based ecosystem: a preliminary study

Movile Cave, a unique groundwater ecosystem in southern Romania, was discovered in 1986. This chemoautotrophic cave contains an abundant and diverse fauna with terrestrial and aquatic invertebrate communities, including 33 endemic species. Since its discovery, studies have focused mainly on cave chemoautotrophic bacteria, while the microfungal community has been largely neglected. In this study, we determined the microfungal species living on various substrates in Movile Cave and compared this spectrum with the mycobiota detected outside the cave (outside air-borne and soil-borne microfungi). To investigate all of the niches, we collected samples for two consecutive years from the dry part of the cave (cave air and sediment, corroded limestone walls, isopod feces, and isopod and spider cadavers) and from the post-siphon part of the cave, i.e., Airbell II (sediment and floating microbial mat). A total of 123 microfungal species were identified from among several hundred isolates. Of these, 96 species were only detected in the cave environment and not outside of the cave, while 90 species were from the dry part of the cave and 28 were from Airbell II. The most diverse genera were Penicillium (at least 18 species) and Aspergillus (14 species), followed by Cladosporium (9 species). Surprisingly, high CFU counts of air-borne microfungi were found inside the cave; they were even higher than outside the cave during the first year of investigation.     

Plant community influences on soil microfungal assemblages in boreal mixed-wood forests

We studied the relationships between assemblages of soil microfungi and plant communities in the southern boreal mixed-wood forests of Quebec. Sampling took place in 18,100 m2 plots from an existing research site. Plots were separated into three categories based on dominant overstory tree species: (i) trembling aspen, (ii) white birch and (iii) a mixture of white spruce and balsam fir. Within each plot a 1 m2 subplot was established in which the understory herbaceous layer was surveyed and soil cores were collected. Microfungi were isolated from soil cores with the soil-washing technique and isolates were identified morphologically. To support our morphological identifications DNA sequences were obtained for the most abundant microfungi. The most frequently occurring microfungal species were Penicillium thomii, P. spinulosum, P. janthinellum, Penicillium sp., P. melinii, Trichoderma polysporum, T. viride, T. hamatum, Mortierella ramanniana, Geomyces pannorum, Cylindrocarpon didymum, Mortierella sp. and Mucor hiemalis. Multivariate analyses (redundancy analysis followed by variance partitioning) revealed that most of the variation in microfungal communities was explained by understory plant species composition as opposed to soil chemistry or overstory tree species. In this floristically diverse system saprophytic microfungal assemblages were not correlated with the overstory tree species but were significantly correlated with the main understory herbs, thereby reflecting differences at a smaller spatial scale.     

Successional Patterns of Microfungi in Fallen Leaves of Ficus pleurocarpa (Moraceae) in an Australian Tropical Rain Forest1

Successional patterns of microfungi on decaying leaves of Ficus pleurocarpa were assessed as part of a study to enumerate microfungi in tropical rain forest leaf litter. Leaves degraded into fragments over a period of 3 mo. Two methods were applied, a direct observational method and a particle filtration protocol. Using a direct method, 104 species were observed, while 53 sporulating taxa and 100 sterile morphotaxa were isolated by particle filtration. Overall patterns of succession were confirmed by both methods, but the relative abundance of species detected differed between the two methods. Nonmetric Multidimensional Scaling identified at least four successional stages and suggested that microfungal communities increased in similarity with advancing decay. Data collected by the direct method indicated a slow but steady decline of diversity with advancing decay, whereas an increase in diversity was detected by particle filtration. Synecological succession studies provide a useful tool to identify patterns and generate hypotheses. Understanding the underlying causes of successional patterns will require further autecological studies.     

Ecology of microfungal communities in gardens of fungus-growing ants (Hymenoptera: Formicidae): a year-long survey of three species of attine ants in Central Texas

We profiled the microfungal communities in gardens of fungus-growing ants to evaluate possible species-specific ant-microfungal associations and to assess the potential dependencies of microfungal diversity on ant foraging behavior. In a 1-year survey, we isolated microfungi from nests of Cyphomyrmex wheeleri, Trachymyrmex septentrionalis and Atta texana in Central Texas. Microfungal prevalence was higher in gardens of C. wheeleri (57%) than in the gardens of T. septentrionalis (46%) and A. texana (35%). Culture-dependent methods coupled with a polyphasic approach of species identification revealed diverse and changing microfungal communities in all the sampling periods. Diversity analyses showed no obvious correlations between the number of observed microfungal species, ant species, or the ants' changing foraging behavior across the seasons. However, both correspondence analysis and 5.8S-rRNA gene unifrac analyses suggested structuring of microfungal communities by ant host. These host-specific differences may reflect in part the three different environments where ants were collected. Most interestingly, the specialized fungal parasite Escovopsis was not isolated from any attine garden in this study near the northernmost limit of the range of attine ants, contrasting with previous studies that indicated a significant incidence of this parasite in ant gardens from Central and South America. The observed differences of microfungal communities in attine gardens suggest that the ants are continuously in contact with a diverse microfungal species assemblage.     

Succession of microfungi in Phillyrea angustifolia litter in a Mediterranean maquis in Sardinia

ABSTRACT

The colonisation of microfungi in litter bags with Phillyrea angustifolia L. leaf litter was followed for two years; the succession of microfungal communities was analysed. Two main groups of fungi were identified, whose presence is correlated with the successive decomposition stages of the substrate and with seasonal variations.     

A new microfungal isolate, Embellisia sp., associated with the Antarctic moss Bryum argenteum

A microfungal isolate of Embellisia sp. (Simmons), assigned Embellisia sp2, not previously described from the Antarctic, has been identified by morphological means and internal transcribed spacer (ITS) region sequencing. Embellisia sp2 was shown to be associated with the bryophyte Bryum argenteum, collected from Marble Point in Southern Victoria Land, Antarctica, and grew only in samples plated from crushed moss tissue and surface-sterilized leafy stems. Two other types of microfungi, Penicillium sp. and Trichoderma sp., were cultivated from a surface rinse of the moss. Accepted: 6 May 2000     

Influence of mineral and organic fertilization on soil fungi,enzyme activities and humic substances in a long-term field experiment

Changes in microfungal communities, fungal activities and humic substances (HS) in agricultural soils kept under different fertilization regimes were observed and their causal relationships were investigated in a long-term field experiment. Fertilization did not change the abundance of HS-utilizing microfungi and, except for organic amendment alone, total culturable microfungi were also unaffected by this factor. Organic fertilization increased activities of manganese peroxidase (MnP) and proteinase, but decreased endo-1,4-beta-glucanase activity compared to the corresponding control without organic fertilization. In soils treated with mineral fertilizers, the activities of MnP, endo-1,4-beta-glucanase and proteinase were higher than in control without any mineral treatment. Both the aromaticity of fulvic acid and the molar mass of humic acid was lower in soil with organic fertilization, which may be a result of oxidative degradation mediated by higher MnP activity observed in treatments with organic fertilization.     

Microfungal Contaminants on Mobile Phones of Health Services Vocational School Students in Marmaris,Turkey

In this study, it was aimed to determine microfungi on mobile phones. Totally, 50 mobile phones were used belonging to Health Services Vocational School students. The samples were taken by swabbing the screen and keys of mobile phones using moistened sterile swab sticks. A total of 24 different microfungal species were obtained belonging to Alternaria, Aspergillus, Cladosporium, Geotrichum, Penicillium, Phoma, Rhinocladiella, Scopulariopsis, Trichoderma, and Trichophyton genera. The genera of microfungi most abundant in terms of the number of species on the mobile phones were Aspergillus, Cladosporium, and Penicillium. Numerically, Cladosporium was found as the most abundant on the mobile phones. Cladosporium herbarum colonies were highest in number, followed by Cladosporium sphaerospermum, and Penicillium verrucosum var. cyclopium. When percentages of each species present on the mobile phones were considered, C. herbarum and C. sphaerospermum were the most common. There was a great similarity between the dominant microfungi isolated from mobile phones and dominant microfungi obtained from studies of atmospheric microfungi in Turkey.     

Fluorescence spectroscopy: a tool to characterize humic substances in soil colonized by microorganisms?

The ability of eight soil microfungal species, Alternaria alternata, Clonostachys rosea f. rosea, Exophiala cf. salmonis, Fusarium cf. coeruleum, Fusarium redolens, Paecilomyces lilacinus, Penicillium canescens and Phoma sp., and two known basidiomycete humic acid (HA) degraders, Trametes versicolor and Phanerochaete chrysosporium, to modify fluorescence properties of fulvic acids (FA) and/or HAs was determined. Effects of minerals and/or glucose on the modifications were examined. FA purified on polyvinyl-polypyrrolidone (PVPP) chromatography column was used. Purification of FA on PVPP column removed the low-molar-mass FA-structural components and excess of extractant (NaOH) used during FA preparation. Excitation spectra of FA entering the purification, purified FA and the removal solution indicate that organic compounds rich in carboxylic groups dominate in the removal solution and higher content of phenolic groups is a characteristic of purified FA. Many microfungal species shifted the emission maximum (measured at 470 and 468 nm of excitation wavelength) of FA, and also HA to longer wavelengths. The opposite effect (shift of the HA emission maximum to shorter wavelengths) of microfungi was observed for HA complemented by glucose. Depending on the presence of glucose in the medium, most microfungi changed also the shape of the emission spectra of HA and FA and the excitation spectra of FA. HA excitation spectrum measured at 590 nm of emission wavelength was significantly affected by the presence of glucose. Mineral ions caused a minor shift in the position of excitation maximum (measured at 590 nm of emission wavelength) toward longer wavelengths.     

Microfungi associated with Abies needles and Betula leaf litter in a subalpine coniferous forest

We investigated microfungal assemblages on leaf litter within a subalpine forest in central Japan and their variation with season, litter depth, and litter species. Microfungal assemblages were compared for Abies needles and Betula leaf litter collected from litter and fermentation layers of the forest floor during the growing season in spring, summer, and autumn. A total of 35 and 42 species were isolated from Abies needles and Betula leaf litter, respectively. The observed variation in microfungal assemblages was primarily attributable to seasonal differences. The frequencies of Trichoderma viride, Volutella ciliata, Mucor sp., and Umbelopsis ramanniana increased in summer, leading to a high degree of similarity of microfungal assemblages in different litter depths and litter species. Microfungal assemblages on Abies needles in spring and autumn and those on Betula leaves in spring were characterized by Trichoderma viride, V. ciliata, Thysanophora penicillioides, Trichoderma polysporum, and (or) Mortierella alpina. Microfungal assemblages on Betula leaves in autumn were characterized by the absence of these species and the occurrence of Cladosporium cladosporioides. The results were discussed with an emphasis on the role of microfungi in decomposition processes and the impact on fungi of predicted future increases in global temperature.     

Studies of pathogenic and antagonistic microfungal populations and their potential interactions in the mycorrhizoplane of Norway spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) on acidified and limed plots

Recent tree decline was hypothesized to be connected to root damage caused by soil acidification and increased frequency of pathogenic root colonizing fungi. The rhizoplane is constituted by the mycorrhizal sheath and a high diversity of microfungi, some of which are known to behave antagonistically against pathogens. Disturbance of the balance between pathogens and antagonists by soil acidification may endanger the health of tree roots. Liming may stabilize the interactions. The microfungal populations connected to the mycorrhizoplane of Norway spruce (Picea abies) and beech (Fagus sylvatica) were, therefore, investigated on experimental Norway spruce plots that had been treated with acidified water or were limed. Beech presented the original forest and was left untreated. Eight microfungal species known as either pathogenic or antagonistic, Trichoderma viride, T. hamatum, T. polysporum, Cylindrocarpon destructans, Sesquicillium candelabrum, Mycelium radicis atrovirens, Tolyplocladium geodes and Oidiodendron maius, were isolated from the mycorrhizoplanes and their abundance in the five different plots compared. Acidification enhanced the frequency of Mycelium radicis atrovirens and Oidiodendron maius but reduced Trichoderma viride. Liming promoted Sesquicillium candelabrum and Cylindrocarpon destructans. Detailed analysis of the population patterns indicated that changes in the frequency of a particular fungal species may not only be caused by shift of chemical soil factors but also by antagonistic interactions between the microfungi, thus reducing pathogenic attacks on rootlets.     

The Role of Soil Seed Banks in Natural Restoration of the Degraded Hunshandak Sandlands, Northern China

The density of seeds in soil seed banks and the species composition of both seed banks and aboveground vegetation were examined in naturally restored sites (NRS) and aerially seeded sites (ASS) in the Hunshandak sandlands of northern China. Five sites were naturally restored 1, 2, 4, 8, and 15 years ago and four sites were aerially seeded 1, 2, 5, and 7 years ago. In total, 36 species were recorded in the seed bank and 41 species in the aboveground vegetation for all NRS, whereas the numbers were 17 and 19, respectively, for ASS, indicating that the NRS can support higher diversity of species than the ASS. During the initial 2 years of restoration, introduced alien shrubs by aerial seeding dominated the vegetation of ASS, although there were indigenous pioneer species in the seed bank which failed to establish in the community. In contrast, indigenous species were dominant components in both the seed bank and the vegetation at the NRS. These findings suggest that the establishment of introduced species might have restricted the germination of certain indigenous pioneer species. Seed bank density of NRS significantly increased with time from 459 ± 76 seeds m⁻² at NRS2 to 3,351 ± 694 seeds m⁻² at NRS15, showing that the seed bank in degraded grassland is large enough to allow natural restoration. It is not always necessary to actively introduce seeds to enhance vegetation diversity.     

On the Potential Contribution of Microfungi to the Decomposition of Reed Leaf Detritus in a Coastal Lagoon: A Laboratory and Field Experiment

The potential contribution of microfungi to reed decomposition in a coastal habitat (Le Cesine Lagoon, Italy) was investigated under laboratory and field conditions. Leaf pack mass and surface loss, ergosterol content and O₂ uptake were used to construct carbon budgets and an empirical ergosterol‐to‐O₂ uptake relationship based on literature data was used to estimate the contribution of microfungi. Under laboratory conditions, reed carbon loss was entirely due to leaching and microbial respiration. In contrast, C losses observed in the field were accounted for by microbial respiration and macroinvertebrate shredding almost equally. Microfungi were estimated to account for 98% and 69% of microbially‐respired carbon under laboratory and field conditions, respectively. Our results provide a preliminary, quantitative assessment of microfungal contribution to reed decomposition in brackish habitats. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Diversity of saprobic microfungi

The data needed to derive an accurate estimate of saprobic microfungi are insufficient, incomplete and contradictory. We therefore address issues that will ultimately reveal whether there are 1.5 million global fungal species, which is the generally accepted working estimate. Our data indicates that large numbers of fungi occur on host families, such as Musaceae, host genera such as Nothofagus and individual host species such as Eucalyptus globulus, and that fungi may be specific or recurrent on different plant groups. Recent studies have shown that fungal numbers on hosts may be larger than originally thought as saprobes are organ-specific/-recurrent and changes in fungal communities occur as substrata decays. Other issues, such as the impact of geography, of methodology and of taxonomy are also addressed. There is evidence that fungi on the same host at different locations also differs; site-specific factors and geographic distance may be more important than host/substrate in shaping fungal assemblages. Methodology impacts on estimates of species diversity with many more taxa observed using indirect isolation protocols as compared to direct isolations from leaves. Our understanding of fungal species numbers in speciose genera is important. In some fungal groups accepted species have been reduced to a few species, while in other groups many cryptic species are being uncovered. While we make a number of generalisations from the studies reported here, this review also highlights some of the limitations mycologists currently have to contend with. A large body of knowledge exists for certain groups of microfungi or for microfungi occurring on certain substrata/hosts. However, it is likely that we are drawing conclusions from data that are somewhat biased toward fungi and host/substrata that are of interest to human endeavours. The discrepancy between the numbers of fungi described from only one economically important genus, Eucalyptus, and all the other members of the Myrtaceae is but one example of this bias. By incorporating the large body of work that is already available and adding appropriate complementary studies, we can accelerate our understanding of microfungal diversity and this will eventually lead us to a realistic estimate of global fungal species numbers.