Characteristics of fungal flora in onion farmlands with potential link to human mycotic keratitis

Acquisition of mycotic keratitis has been linked to agricultural activities. Although fungi were identified in injured eyes, data derived directly from farmlands are limited. Following five cases of fungal corneal ulcers in onion harvesters in the monsoon area of Taiwan, the present study further determined fungi genera and their concentrations in onion crops and surface soils of onion farmlands. In total, 52, 100 and 100 samples of soils, onion leaves and bulb scales, respectively, were collected from three monsoon and one non-monsoon farmlands. Fungal colonies were counted and microscopically examined after incubation at 25°C for 4–7 days on malt extract agar with 40?g?mL^?1 chloramphenicol. Results showed the peak fungi levels were mostly observed at harvest time. Among keratitis-related fungi, Aspergillus predominated in soils as well as in onion bulb scales, while Alternaria in onion leaves. Cladosporium was also prevalent in soils, onion leaves and scales. Other keratitis-related fungi included Acremonium, Curvalaria, Fusarium, Mycelia, Penicillium, Rhizoctonia and Rhizopus. The present study provides an exposure link between onion harvesters and presence of keratitis-related fungi from onion crops and soils, which may account for mycotic ocular infection via hand-to-eye contact and airborne transmission during the monsoon season.     

Cytotoxic and proinflammatory response of RAW 264.7 cells to differentially fractionated fungal fragments

Although significant research has been carried out for studying the impacts of pure mycotoxins on human cell, little information is known about the direct effects of fungal submicron particles. In this report, murine macrophage RAW 264.7 cells were exposed to fungal extracts from Stachybotrys chartarum RTI 5802 and Aspergillus versicolor RTI 3843 as well as mixtures from both fungi with fragment sizes ranging from 0.25 to 1?µm. Cell viability was found to be unaffected by all extracts except fragments in the 0.5–1?µm size range from A. versicolor RTI 3843, which decreased cell viability by approximately 60%. IL-1β expression was generally upregulated following exposure to fungal extracts from either S. chartarum RTI 5802 or A. versicolor RTI 3843. However, when extracts from the mixture of both fungi were introduced, IL-1β expression was downregulated. IL-6 and IL-10 expression were also generally upregulated. In comparison to the findings in the literature about the effects of pure mycotoxins on RAW 264.7 cells, the results presented herein show different patterns on mRNA expression which may be a result of the complex composition of the extract in terms of both mycotoxins and other fungal materials in addition to the potential interplay of the different components.     

菌根类型对森林树木净初级生产力的影响

菌根是土壤真菌与植物根系形成的共生体,存在于绝大多数植物（90%）的根系和生境中。菌根共有7种类型,在生态系统的过程和功能方面都扮演着十分重要的角色。为了增强对菌根在森林生态系统中重要功能的理解,文章基于全球森林数据库,在全球尺度上研究了不同菌根类型对森林树木净初级生产力（NPP）的影响。结果表明,森林树木NPP随菌根类型的不同而不同,AM类型菌根森林的NPP[679.49 g.m-2.a-1（以C计）]要显著高于含ECM类型菌根的森林[479.00 g.m-2.a-1（以C计）];菌根类型的不同对森林树木地上和地下及其各组分NPP的影响和贡献也存在着显著的不同,AM类型菌根对地下NPP的贡献要高于ECM菌根,而ECM菌根对地上NPP的贡献则较大。菌根类型对地上、地下NPP组分的影响分析则表明,AM类型的菌根对树叶和细根NPP的贡献较大,而ECM类型菌根则对树木主干和枝NPP的贡献较大。可见,森林树木总体NPP及其各组分NPP都随着菌根类型的不同而存在显著的差异。     

Studies on the influence of mycorrhiza on the growth and physiology of Vigna unguiculata and Abelmoschus esculentus

Diverse forms of microorganisms present in the soil and near the roots of plants, which play a vital role in numerous physiological processes, have attracted the attention of scientists. The dynamic microbial associations may be saprophytic, pathogenic, or symbiotic. The most widespread symbiosis of plants is the mycorrhizal association between root-inhabiting fungi and the feeder roots of plants. The present study was conducted to study the effects of arbuscular mycorrhizal fungi on mineral nutrition of Vigna unguiculata and Abelmoschus esculentus. The experiment comprised of uninoculated seedlings and seedlings inoculated with Glomus mosseae. The chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein, nitrate, nitrogen, and phosphorus content showed an increase in vesicular arbuscular mycorrhiza fungus-treated seedlings compared to non-mycorrhizal plants. The total soluble sugars and soluble starch content in leaves of all selected plant species in the present study showed a decrease in mycorrhizal seedlings compared to non-mycorrhizal seedlings.     

Marine fungi (Ascomycetes) within and on tests of Foraminifera

Fruiting bodies of higher marine fungi occur within and on tests of foraminiferans on tropical beaches of the Pacific (Australia, Hawaii) and Atlantic Ocean (Belize, Mexico). Ascocarps (fruiting bodies ) of five intertidal species or varieties of the genera Arenariomyces, Corollospora and Lindra colonize foraminiferans in the natural habitat and may contribute to the eventual breakup of the tests. Fungal fruiting structures, which are normally subglobose when developing in other substrates, adjust to the shape of the foraminiferan chambers when growing within the tests. Pure cultures of L. thalassiae var. crassa yielded the same type of irregular fruiting bodies when grown at 30° C on foraminiferan tests as the sole source of nutrients.Smithsonian Contribution No. 174 (Investigations of Marine Shallow-Water Ecosystems Program, Reef and Mangrove Study-Belize)     

Carbon allocation to ectomycorrhizal fungi correlates with belowground allocation in culture studies

Ectomycorrhizal fungi form symbioses with most temperate and boreal tree species, but difficulties in measuring carbon allocation to these symbionts have prevented the assessment of their importance in forest ecosystems. Here, I surveyed allocation patterns in 14 culture studies and five field studies of ectomycorrhizal plants. In culture studies, allocation to ectomycorrhizal fungi (NPPf) was linearly related to total belowground net primary production (NPPb) by the equation NPPf = 41.5% x NPPb - 11.3% (r2 = 0.55, P < 0.001) and ranged from 1% to 21% of total net primary production. As a percentage of NPP, allocation to ectomycorrhizal fungi was highest at lowest plant growth rates and lowest nutrient availabilities. Because total belowground allocation can be estimated using carbon balance techniques, these relationships should allow ecologists to incorporate mycorrhizal fungi into existing ecosystem models. In field studies, allocation to ectomycorrhizal fungi ranged from 0% to 22% of total allocation, but wide differences in measurement techniques made intercomparisons difficult. Techniques such as fungal in-growth cores, root branching-order studies, and isotopic analyses could refine our estimates of turnover rates of fine roots, mycorrhizae, and extraradical hyphae. Together with ecosystem modeling, such techniques could soon provide good estimates of the relative importance of root vs. fungal allocation in belowground carbon budgets.     

Impact of deltamethrin on the endophytic fungal community of a Chinese cabbage,Brassica chinensis

Endophytic fungi, being closely associated with their host plants, are an important part of the ecosystem and food web. In modern agriculture, pesticides are widely used. The impact of pesticides on the endophytic fungal community of crops remains poorly understood. In this paper, Chinese cabbage Brassica chinensis, a popular leafy vegetable consumed worldwide, was selected for evaluating the potential effects of a pesticide, deltamethrin, on the endophytic fungal community. By culture method, 195 endophytic fungal strains classified into 39 taxa and 186 strains classified into 30 taxa, respectively, were isolated from the pesticide-treated and untreated B. chinensis samples. Sirodesmium spp. were the predominant endophytic fungi from both samples. The colonisation rates of endophytic fungi of the treated and the untreated samples were not significantly different, as determined by one-way analysis of variance (p?>?.05). The Shannon diversity indexes (H′) were close, being 2.216 and 2.152, respectively. However, the endophyte compositions of the treated and the untreated samples were significantly different (p?B. chinensis.     

Mycorrhizal benefit differs among the sexes in a gynodioecious species

Both plant sex and arbuscular mycorrhizal (AM) symbiosis influence resource acquisition and allocation in plants, but the interaction between these two components is not well established. As the different plant sexes differ in their resource needs and allocation patterns, it is logical to presume that they might differ in their relationship with AM as well. We investigate whether the association with AM symbiosis is different according to the host plant sex in the gynodioecious Geranium sylvaticum, of which, besides female and hermaphrodite plants, intermediate plants are also recognized. Specifically, we examine the effects of two different AM fungi in plant mass allocation and phosphorus acquisition using a factorial greenhouse/common garden experiment. Cloned G. sylvaticum material was grown in symbiosis with AM fungi or in non-mycorrhizal condition. We evaluated both the symbiotic plant benefit in terms of plant mass and plant P content and the fungal benefit in terms of AM colonization intensity in the plant roots and spore production. Our results suggest that G. sylvaticum plants benefit from the symbiosis with both AM fungal species tested but that the benefits gained from the symbiosis depend on the sex of the plant and on the trait investigated. Hermaphrodites suffered most from the lack of AM symbiosis as the proportion of flowering plants was dramatically reduced by the absence of AM fungi. However, females and intermediates benefited from the symbiosis relatively more than hermaphrodites in terms of higher P acquisition. The two AM fungal species differed in the amount of resources accumulated, and the fungal benefit was also dependent on the sex of the host plant. This study provides the first evidence of sex-specific benefits from mycorrhizal symbiosis in a gynodioecious plant species.     

Antifungal activity of volatile metabolites emitted by mycelial cultures of saprophytic fungi

The antifungal activity of molecular identified Chilean saprobiontic fungi, Trichoderma viride, Schizophyllum commune and Trametes versicolor, on the fungal plant pathogens Botrytis cinerea and Fusarium oxysporum, and the saprotrophic mould Mucor miehei was investigated using two types of inhibition bioassay: (1) bi-compartmented Petri dishes and (2) two Erlenmeyer flasks connected by their upper parts. The chemical composition of volatile organic compounds (VOCs) released by saprobiontic fungi was also investigated using headspace solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC-MS) analysis. Of the saprobiontic fungi evaluated, one isolate of S. commune showed the highest inhibitory activity against B. cinerea and M. miehei, 86.0±5.4 and 99.5±0.5% respectively. The volatile profiles of fungal isolates were shown to contain a different class of compounds. The major components in the headspace of mycelial cultures were 6-pentyl-α -pyrone (T. viride), ethanol and β -bisabolol (S. commune), and a sesquiterpene alcohol (Tr. versicolor). This is the first study reported on the release of VOCs by Chilean native fungi and their antifungal activity wrt. plant pathogenic fungi.     

Orchid-fungus fidelity: a marriage meant to last?

The characteristics of plant-mycorrhizae associations are known to vary in both time and space, but the ecological consequences of variation in the dynamics of plant-fungus interactions are poorly understood. For example, do plants associate with single fungi or multiple fungi simultaneously, and do the associations persist through a plant's lifetime or do plants support a succession of different fungi? We investigated these and other questions related to plant-fungus interactions in Goodyera pubescens, an evergreen terrestrial orchid of the eastern United States, that interacts with closely related fungi in the genus Tulasnella. Unlike the mycorrhizal associations of other plants, orchid-mycorrhizal associations only benefit the orchid, based on current evidence. Many terrestrial orchids have been found to associate with specific groups of fungi. This characteristic could potentially limit orchids to relatively narrow ranges of environmental conditions and may be a contributing factor in the decline of many orchids in the face of changing environmental conditions. We found that G. pubescens protocorms (developing embryos prior to leaf production) and adults associated with only one fungal individual at a time. The orchid-fungus association persists for years, but during a drought period that was associated with the death of many plants, surviving plants were able to switch to new fungal individuals. These results suggest that G. pubescens interacts with the same fungal partner during periods of modest environmental variation but is able to switch to a different fungal partner. We hypothesize that the ability to switch fungi allows G. pubescens to survive more extreme environmental perturbations. However, laboratory experiments suggest that switching fungi has potential costs, as it increases the risk of mortality, especially for smaller individuals. Our findings indicate that it is unlikely that switching fungi is a common way to improve tolerance of less severe environmental fluctuations and disturbances. These findings may have important implications for plant responses to severe climatic events or to more gradual environmental changes such as global warming.     

Distinct mycorrhizal communities on new and established hosts in a transitional tropical plant community

The extent to which interspecific plants share mycorrhizal fungal communities depends on the specificity of the symbiosis. For tropical forest tree seedlings, colonization by mycorrhizal fungi associated with established vegetation could have important consequences for survival and growth. I used a novel molecular technique to assess the potential for sharing of mycorrhizas in forest and pasture in southern Costa Rica, by identifying arbuscular mycorrhizal (AM) fungi in roots of the forest canopy tree species Terminalia amazonia, pasture grasses Urochloa ruziziensis and U. decumbens, and seedlings of T. amazonia planted into experimental reforestation plots. I tested the hypotheses that experimental seedlings were colonized either by the AM fungal community of the forest T. amazonia (suggesting host specificity) or of Urochloa (suggesting absence of specificity/importance of local environment). After two years, pasture-grown T. amazonia seedlings were colonized by neither community, but rather by a species of Glomus that was rarely observed on the other plants. These results suggest that conspecific seedlings planted into existing vegetation generate a distinct mycorrhizal community that may influence competitive interactions and the relative costs and benefits of the AM fungal symbiosis at early stages in the life cycle of tropical trees.     

Ozone‐induced xeromorphism of beech leaves (Fagus sylvatica L.)

The influence of different concentrations of ozone under different light intensities on young trees of European beech (Fagus sylvatica L.) is studied. Young beeches were exposed continuously for 5 months in fumigation chambers, located outdoors, with 131±30/μg/m³O₃, and for 2 months in fumigation chambers, located in air‐conditioned greenhoouses, with 100±10, 200±20 and 300±30/μg/m³O₃, respectively. The observed symptoms point towards an increased xeromorphism in beech leaves, positively influenced by high light intensities. Ozone‐induced water stress may be the cause of xeromorphic tissue changes. On the ultrastructural level chloroplasts have become senescent.     

Role of arbuscular mycorrhizal fungi on the performance of floodplain Phragmites japonica under nutrient stress condition

A pot experiment was conducted to evaluate the potential effects of arbuscular mycorrhizal fungi (AMF) on growth, nutrient uptake, and inoculation effectiveness on Phragmites japonica. Spores of AMF strains (Gigaspora margarita Becker &; Hall) were collected from the commercial product ‘Serakinkon’. Four treatments, namely, natural soil (NS), natural soil inoculated by AM fungi, sterilised soil (SS) inoculated by AM fungi, and SS without AM fungi inoculation were selected to determine the effects of applied and indigenous AMF on P. japonica. The average colonisation level of P. japonica was 24–33%, whereas no colonisation was found in the SS. AMF colonisation increased the chlorophyll content (r?=?0.84, p?r?=?0.89, p?相似文献   

Screening for plants and rhizospheral fungi with bioremediation potency of petroleum-polluted soils in a Tehran oil refinery area

The contamination of soils by toxic and/or hazardous organic pollutants, especially with crude oil, is a widespread problem. This study was conducted in a petroleum-contaminated area in a Tehran oil refinery to find petroleum-resistant plants and their rhizospheral fungal strains with bioremediation potency. The plants growing in the oil-polluted area were collected and determined taxonomically. Root samples of the plant species were collected from a polluted area and fungal strains determined by laboratory methods and taxonomical keys. The growth ability of the isolated fungal strains was studied in media containing 1%–15% crude oil. Results showed that seven plant species were of the highest density in the contaminated area: Alhagi persarum, Hordeum marinum, Peganum harmala, Phragmites australis, Prosopis farcta, Salsola kali, and Senecio glaucus. The root-associated fungi were isolated and showed that the fungal variation in the oil-polluted area is higher than that in a non-polluted area. The growth assay of isolated fungal strains showed that all studied fungal strains were able to form colonies at the applied concentrations but Alternaria sp. and Rhizopus sp. were the most resistant ones. Some plants were resistant to oil pollution, which also had positive effects on the fungal strains.     

丛枝菌根真菌对内蒙古草原大针茅群落的影响

使用真菌抑制剂在内蒙古草原开展原位试验,人为创造菌根受抑制和正常两种环境,通过分析菌根侵染率,测定大针茅群落的物种组成、丰富度和多样性等结构指标,分析丛枝菌根真菌对群落结构和净初级生产力的影响。试验结果表明,两种处理群落的菌根侵染率不同,苯菌灵有效地降低了植株的菌根侵染率。丛枝菌根真菌短期内未能对植物群落的物种丰富度、多样性产生影响,未能改变植物群落的结构和净初级生产力。但丛枝菌根真菌的存在,会对植物群落内不同植物种的地上部生物量实现再分配,降低了优势种垄断资源的能力,使群落内物种的生物量和营养元素含量趋于均匀,有利于保护关键种,有利于植被的恢复与重建。因此,研究结论为内蒙古退化草原生态系统的恢复和重建提供了重要的理论依据和参考价值。     

Disrupting mycorrhizal mutualisms: a potential mechanism by which exotic tamarisk outcompetes native cottonwoods

The disruption of mutualisms between plants and mycorrhizal fungi is a potentially powerful mechanism by which invasives can negatively impact native species, yet our understanding of this mechanism's role in exotic species invasion is still in its infancy. Here, we provide several lines of evidence indicating that invasive tamarisk (Tamarix sp.) negatively affects native cottonwoods (Populus fremontii) by disrupting their associations with arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi. At a field site in the early stages of tamarisk invasion, cottonwoods with tamarisk neighbors had reduced EM colonization and altered EM fungal community composition relative to cottonwoods with native neighbors, leading to reductions in EM propagule abundance in the soil beneath tamarisk. Similarly, AM colonization of cottonwoods was reduced with a tamarisk neighbor, but there were no significant changes in AM fungal spore communities or propagule abundance. Root colonization by nonmycorrhizal fungi, including potential pathogens, was higher in cottonwoods with tamarisk neighbors. A greenhouse experiment in which AM and EM inoculation and plant neighbor were manipulated in a fully factorial design showed that cottonwoods benefited from mycorrhizas, especially EM, in terms of shoot biomass when grown with a conspecific, but shoot biomass was similar to that of nonmycorrhizal controls when cottonwoods were grown with a tamarisk neighbor. These results are partially explained by a reduction in EM but not AM colonization of cottonwoods by a tamarisk neighbor. Tamarisk neighbors negatively affected cottonwood specific leaf area, but not chlorophyll content, in the field. To pinpoint a mechanism for these changes, we measured soil chemistry in the field and the growth response of an EM fungus (Hebeloma crustuliniforme) to salt-amended media in the laboratory. Tamarisk increased both NO3- concentrations and electrical conductivity 2.5-fold beneath neighboring cottonwoods in the field. Salt-amended media did not affect the growth of H. crustuliniforme. Our findings demonstrate that a nonnative species, even in the early stages of invasion, can negatively affect a native species by disrupting its mycorrhizal symbioses. Some of these changes in mycorrhizal fungal communities may remain as legacy effects of invasives, even after their removal, and should be considered in management and restoration efforts.     

Removal,adsorption and desorption of pentachlorophenol (PCP) by filamentous fungi: Rhizopusarrhizus and Cunninghamella elegans in batch system

PCP was, and in some countries still is, one of the most frequently used fungicides and pesticides, specially in wood preservation. The extensive use is correlated with contamination of water and soil and it is detected in several compartments of the food chain.

Some Micromycetes are able to adsorb and degrade PCP, with two mechanisms involved: biosorption (including both adsorption and absorption) and biodegradation.

Our work is focused on the biosorption alone and biodegradation‐biosorption of PCP by respectively denatured and living R.arrhizus and C.elegans fungi.

Living fungi are cultivated in batch system and denaturation is obtained by drying (70°C) and grinding the fungi to a calibrated powder (200–400 μm). Kinetic studies are performed with 10 mg/1 PCP initial concentration. Adsorption capacity is measured at equilibrium concentration as high as about 400 mg/1 PCP.

The results show that: PCP adsorption, for the two fungi, follows a two steps process. R. arrhizus dead and living biomasses are able to bind respectively, 75 and 55% of a 10 mg/1 PCP initial concentration in 1 hour contact time and then 75 and 100% in 96 hours. For C.elegans, 70 and 28% in 1 hour and in 96 hours 70 and 90%, respectively.

The PCP binding by living fungi is higher than non living ones, but with a slower rate.

The maximum PCP adsorption capacity is about 24 mg/g of R.arrhizus dried biomasses and 16 mg/g for C.elegans ones, in 48 hours contact time. Isotherm curves follow the Langmuir model.

Desorption studies with methanol (to reuse biomasses) shows that it is a rapid phenomenon (about 100% in 24 hours for the two fungi).

An industrial and economical process to depollute contaminated water by PCP is possible by using cheap fungal by‐products from fermentation industries.     

丛枝菌根真菌与重金属的相互作用对玉米根际微生物数量和磷酸酶活性的影响

以玉米为供试植物 ,研究了砂培条件下不同丛枝菌根真菌 (Acaulosporalaevis,Glomuscaledonium ,Glomusmanihotis)与不同浓度重金属 (铜和镉 )的相互作用对菌根侵染率、孢子数、根际微生物数量和磷酸酶活性的影响 .在不同浓度的铜和镉中 ,G .caledonium的侵染率均最高 ,且随重金属浓度的增加而变化较小 ,而它的孢子数在这 3种接种处理中最低 .低量的铜 (0 .0 5mg/kg)可显著地减少不接种、接种A .laevis和G .manihotis的细菌数量 ,却能显著地增加接种处理的真菌数量 .当溶液中铜的浓度大于 0 .2mg/kg时 ,接种处理的真菌数量小于不接种处理的真菌数量 .铜或镉的浓度不同时放线菌数量均有接种远大于不接种 ,其中接种之间放线菌数量相差不大 ,且随重金属浓度增大而变化较小 .无论是不同浓度的铜还是不同浓度的镉的接种处理常有利于增加磷酸酶活性 .重金属浓度低时 ,细菌和真菌数量、磷酸酶活性变化较大 ,高浓度时变化较小 .图 7参 15     

Mutualistic stability in the arbuscular mycorrhizal symbiosis: exploring hypotheses of evolutionary cooperation

The 450-million-year-old symbiosis between the majority of land plants and arbuscular mycorrhizal fungi (AMF) is one of the most ancient, abundant, and ecologically important mutualisms on Earth. Yet, the evolutionary stability of mycorrhizal associations is still poorly understood, as it follows none of the constraints thought to stabilize cooperation in other well-known mutualisms. The capacity of both host and symbiont to simultaneously interact with several partners introduces a unique dilemma; detecting and punishing those exploiting the mutualism becomes increasingly difficult if these individuals can continue to access resources from alternative sources. Here, we explore four hypotheses to explain evolutionary cooperation in the arbuscular mycorrhizal symbiosis: (1) pseudo-vertical transmission and spatial structuring of plant and fungal populations leading to local adaptation of partners; (2) luxury resource exchange in which plants trade surplus carbon for excess fungal nutrients; (3) partner choice allowing partners to associate with better cooperators; and (4) host and symbiont sanctions which actively reward good partners and punish less cooperative ones. We propose that mycorrhizal cooperation is promoted by an exchange of surplus resources between partners and enforced through sanctions by one or both partners. These mechanisms may allow plant and fungal genotypes to discriminate against individuals employing exploitative strategies, promoting patterns of partner choice. Together these selection pressures provide a framework for understanding the stabilization of mycorrhizal cooperation over evolutionary time.     

Cellular damage of plant pathogenic fungi by antifungal compounds produced by Bacillus spp. isolates

The use of microorganisms as biological control agents (BCAs) has become an effective alternative to chemical means of controlling plant pathogens. The antagonistic and inhibitory activity of 71 Bacillus spp. strains, which were isolated from different Mexican sites, were tested against several phytopathogen fungi, Fusarium oxysporum, Fusarium equiseti, Fusarium avenaceum, Bipolaris spp. and Alternaria spp. From the antagonism study, the strain ELI149 showed a marked inhibition of growth against all tested fungi; therefore crude metabolites from this strain were extracted using ethyl acetate and amberlite resin and probed against the same fungi as well as strains of Mucor sp., Penicillium spp. and Paecilomyces spp. The results indicated that amberlite was more suitable for extraction of secondary metabolites with antifungal activity. Finally, observation of cell damage in the tested pathogenic fungi showed marked morphological changes on reproductive structures in all tested fungi indicating that antibiosis was the mechanism of the antagonistic effect. These results suggest that metabolites from the Bacillus strains have a wide spectrum of antibiotic activities, which can be used as biocontrol agents for controlling fungal plant diseases of agricultural importance.