Rapid method for the determination of ochratoxin A in urine by immunoaffinity column clean-up and high-performance liquid chromatography

Buildings with poor indoor air quality (IAQ) frequently have many areas with surface fungal contamination. Studies have demonstrated that certain fungal genera (e.g., Cladosporium, Penicillium, and Stachybotrys) are able to grow on building materials such as wallpaper, drywall, and ceiling tiles, particularly after water damage has occurred. Due to the increasing awareness of sick building syndrome (SBS), it has become essential to identify building materials that prevent the interior growth of fungi. The objective of this study was to identify building materials that would not support the growth of certain fungal genera, regardless of whether an external food source was made available. The growth of three fungal genera (Cladosporium, Penicillium, and Stachybotrys) was evaluated on cellulose-containing ceiling tile (CCT) and inorganic ceiling tile (ICT). Both types of ceiling tile were exposed to environmental conditions which can occur inside a building. Our results show that ICT did not support the growth of these three fungal genera while CCT did. Our data demonstrate that ICT could serve as an ideal replacement for CCT. This revised version was published online in June 2006 with corrections to the Cover Date.     

The rich and the sensitive: diverse fungal communities change functionally with the warming Arctic

Fungi are very abundant and functionally pivotal in Arctic terrestrial ecosystems. Yet, our understanding of their community composition, diversity and particularly their environmental drivers is superficial at the very best. In this issue of Molecular Ecology, Timling et al. ( 2014 ) describe perhaps one of the most comprehensive and geographically ambitious molecular studies on Arctic fungal communities to date. The results highlight the potential sensitivity of the fungal communities to plant communities, environmental conditions and therefore to environmental change. Thus, these studies lay a foundation to educated speculation on the fungal community migration northwards as a result of predicted climate change.     

Contrasted ecological niches shape fungal and prokaryotic community structure in mangroves sediments

Mangroves are forest ecosystems located at the interface between land and sea where sediments presented a variety of contrasted environmental conditions (i.e. oxic/anoxic, non-sulfidic/sulfidic, organic matter content) providing an ideal ecosystem to study microbial communities with niche differentiation and distinct community structures. In this work, prokaryotic and fungal compositions were investigated during both wet and dry seasons in New Caledonian mangrove sediments, from the surface to deeper horizons under the two most common tree species in this region (Avicennia marina and Rhizophora stylosa), using high-throughput sequencing. Our results showed that Bacteria and Archaea communities were mainly shaped by sediment depth while the fungal community was almost evenly distributed according to sediment depth, vegetation cover and season. A detailed analysis of prokaryotic and fungal phyla showed a dominance of Ascomycota over Basidiomycota whatever the compartment, while there was a clear shift in prokaryotic composition. Some prokaryotic phyla were enriched in surface layers such as Proteobacteria, Euryarchaeota while others were mostly associated with deeper layers as Chloroflexi, Bathyarchaeota, Aminicenantes. Our results highlight the importance of considering fungal and prokaryotic counterparts for a better understanding of the microbial succession involved in plant organic matter decomposition in tropical coastal sediments.     

Bioaerosol assessment in the library of Istanbul University and fungal flora associated with paper deterioration

Health problems in people who are in indoor environments with poor ventilation have resulted in an increase in the number of studies regarding air quality. Microorganisms and inferior indoor air-climatic conditions not only affect human health but also cause decay of invaluable materials present in libraries. Therefore, this study aimed to assess the culturable bioaerosol composition and concentration in the library of Istanbul University. The culturable fungal flora, a biodeterioration agent, of the damaged archival materials was also examined. The air was sampled for a year, as were the surfaces of 207 biologically damaged books. The fungal colonies’ range was between 235 and 1850 CFU/m³, and the bacterial colonies range between 270 and 1920 CFU/m³. This is the first volumetric record in Turkey. Although the microbial contamination was not very high, molds such as Aspergillus versicolor, Cladosporium sphaerospermum, Penicillium chrysogenum, Alternaria alternata, Chaetomium globosum, Aspergillus flavus, and Aspergillus ochraceus might cause harm to human beings or to books as biodeterioration agents. The highest amount of fungus was determined in Archive 3, which contained damaged books. The fungal species isolated from the air and books were essentially the same. Therefore, it is important to determine not only the numeric values but also the microbiological composition of fungal colonies because the variety of fungal species is indicative of a deterioration process in effect over a long period. The deterioration of books must be remedied.     

An Antarctic Hot Spot for Fungi at Shackleton's Historic Hut on Cape Royds

The historic expedition huts located in the Ross Sea Region of the Antarctic and the thousands of artifacts left behind by the early explorers represent important cultural heritage from the “Heroic Era” of Polar exploration. The hut at Cape Royds built by Ernest Shackleton and members of the 1907–1908 British Antarctic Expedition has survived the extreme Antarctic environment for over 100 years, but recent studies have shown many forms of deterioration are causing serious problems, and microbial degradation is evident in the historic wood. Conservation work to reduce moisture at the hut required removal of fodder, wood, and many different types of organic materials from the stables area on the north side of the structure allowing large numbers of samples to be obtained for these investigations. In addition, wood from historic food storage boxes exposed in a ravine adjacent to the hut were also sampled. Fungi were cultured on several different media, and pure cultures were obtained and identified by sequencing of the internal transcribed spacer region of rDNA. From the 69 cultures of filamentous fungi obtained, the most predominant genera were Cadophora (44%) followed by Thielavia (17%) and Geomyces (15%). Other fungi found included Cladosporium, Chaetomium, and isolates identified as being in Pezizomycotina, Onygenales, Nectriaceae, and others. No filamentous basidiomycetes were found. Phylogenetic analyses of the Cadophora species showed great species diversity present revealing Cadophora malorum, Cadophora luteo-olivacea, Cadophora fastigiata, as well as Cadophora sp. 4E71-1, a C. malorum-like species, and Cadophora sp. 7R16-1, a C. fastigiata-like species. Scanning electron microscopy showed extensive decay was present in the wood samples with type 1 and type 2 forms of soft rot evident in pine and birch wood, respectively. Fungi causing decay in the historic wooden structures and artifacts are of great concern, and this investigation provides insight into the identity and species diversity of fungi found at the site. The historic woods and other organic materials at this site represent a large input of carbon into the Antarctic environment. This as well as nutrient additions from the nearby Adélie penguin (Pygoscelis adeliae) colony and favorable conditions for fungal growth at Cape Royds appear responsible for the significant fungal diversity, and where extensive decay is taking place in wood in contact with the ground.     

Interactions between bacteria and fungi in macrophyte leaf litter decomposition

Microbes play an important role in decomposition of macrophytes in shallow lakes, and the process can be greatly affected by bacteria–fungi interactions in response to material composition and environmental conditions. In this study, microbes involved in the decomposition of leaf litter from three macrophyte species, Zizania latifolia, Hydrilla verticillata and Nymphoides peltata, were analysed at temperatures of 5, 15 and 25 °C. Results indicate that the decomposition rate was affected by temperature. Bacterial alpha diversity increased significantly along the time, while both temperature and plant species had a significant impact on the bacterial community, and plant type was shown to be the most important driving factor for the fungal community. The cosmopolitan bacterial taxa affiliated with Gammaproteobacteria, Bacteroidetes, Deltaproteobacteria, Firmicutes and Spirochaetes were key species in the investigated ecological networks, demonstrating significant co-occurrence or co-exclusion relationships with Basidiomycota and Ascomycota, according to different macrophyte species. This study indicates that bacteria involved in the decomposition of macrophyte leaf litter are more sensitive to temperature variance, and that fungi have a higher specificity to the composition of plant materials. The nutrient content of Hydrilla verticillata promoted a positive bacteria–fungi interaction, thereby accelerating the decomposition and re-circulation of leaf litter.     

Impacts of abiotic factors on the fungal communities of ‘Honeycrisp’ apples in Canada

The maintenance of the beneficial plant microbiome to control plant pathogens is an emerging concept of disease management, and necessitates a clear understanding of these microbial communities and the environmental factors that affect their diversity and compositional structure. As such, studies investigating the microbiome of economically significant cultivars within each growing region are necessary to develop adequate disease management strategies. Here, we assessed the relative impacts of growing season, management strategy, and geographical location on the fungal microbiome of ‘Honeycrisp’ apples from seven different orchard locations in the Atlantic Maritime Ecozone for two consecutive growing years. Though apple fruit tissue was dominated by relatively few fungal genera, significant changes in their fungal communities were observed as a result of environmental factors, including shifts in genera with plant-associated lifestyles (symbionts and pathogens), such as Aureobasidium, Alternaria, Penicillium, Diplodia, and Mycosphaerella. Variation in fungal composition between different tissues of fruit was also observed. We demonstrate that growing season is the most significant factor affecting fungal community structure and diversity of apple fruit, suggesting that future microbiome studies should take place for multiple growing seasons to better represent the host–microbiome of perennial crops under different environmental conditions.     

Soil Fungal Diversity and Community Composition in Response to Continuous Sweet Potato Cropping Practices

Soil fungi are extremely important for maintaining soil health and plant production in agricultural systems. Currently, the effect of continuous cropping of sweet potato on soil fungal communities and physiochemical parameters has not been well documented. In the present study, four sweet potato fields consecutively monocultured for 1, 2, 3, and 4 years were selected to investigate the effect of monoculture on soil fungal communities through Illumina MiSeq sequencing. Continuous cropping of sweet potatoes dramatically altered the fungal community composition, whereas fungal diversity was almost unchanged. Ascomycota and Basidiomycota were the most abundant phyla in all soil samples, accounting for 32.59% and 21.14% of the average relative abundance, respectively. The abundance of some potential pathogens, such as Ascobolus spp, specifically Ascobolus stercorarius, and some unknown fungi increased significantly as the sweet potato monoculture period increased, and their presence were highly positively correlated with disease incidence. In contrast, Basidiomycota, Bullera, Fusarium and Trichocladium most likely play roles as antagonists of sweet potato disease development, as their relative abundance decreased significantly over time and were negatively correlated with disease incidence. Redundancy and correlation analyses revealed that soil pH and organic carbon content were the most important factors driving these changes. Our findings provided a dynamic overview of the fungal community and presented a clear scope for screening beneficial fungi and pathogens of sweet potato.     

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.     

Study of airborne fungal spores in Madrid, Spain

The concentration of fungal spores in the atmosphere of Madrid was recorded and analyzed for the year 2003. Airborne spores were sampled continuously with a Hirst-type spore trap located on the roof of a building of the School of Pharmacy, at about 8 m above ground level. Correlation between the mean daily spore concentrations and meteorological variables were explored by means of Spearman’s correlation analyses. Seventy spore types were identified, of which the most numerous were Cladosporium, Aspergillaceae (conidia), Coprinus, Agaricales (basidiospores), Ustilago (teliospores) and Pleospora (ascospores). These six types of spores represented more than 70% of the total. Cladosporium represented 41% of the total fungal spores, while Ustilago spores, the concentrations of which in May and June exceeded 47% of the monthly total spore count, constituted the second most important group. Spores reached their highest concentrations in the spring months, and in the autumn, mainly in October. A␣positive significant correlation was found between airborne spore counts and temperature and relative humidity. The results provide a picture of the spectrum of airborne fungal spores present in the atmosphere of Madrid and of the `peak' periods of their presence. Future studies will provide more detailed information on the seasonal dynamics of the spores most frequently found in the air as well as on the extent to which atmospheric conditions influence their release, dispersion and sedimentation processes.     

丛枝菌根真菌群落沿高寒草原海拔梯度的变化特征

基于丛枝菌根(Arbuscular mycorrhizal,AM)真菌孢子形态学的鉴定,对沿不同海拔(4584、4628、4744、4880、4956 m)梯度采集的高寒草原建群植物根际土壤样品进行了分析。结果表明,高寒草原AM真菌属、种构成均较简单,Acaulospora、Claroideoglomus、Funneliformis、Glomus属见于各海拔梯度,海拔4744 m地带未见Pacispora属,海拔4744、4956 m地带无Scutellospora属分布,Rhizophagus属仅见于海拔4584 m地带。随海拔上升,AM真菌种数、物种丰度均呈显著下降;海拔4584—4880 m范围Shannon-Weiner指数(H)无显著差异,但在最高海拔时显著下降;优势种种数及所占比例与海拔梯度则呈显著正相关(Funneliformis geosporum、Claroideoglomus claroideum为不同海拔梯度优势种);沿海拔梯度,孢子密度基本呈单峰分布格局,峰值出现在海拔4744 m地带;海拔梯度对菌根侵染效应影响显著,菌根侵染率、侵染强度和丛枝丰度随海拔上升均呈显著下降趋势;不同海拔梯度高寒草原AM真菌群落相似度(Sorensen相似性系数0.821—0.969)较高,并在总体上表现出随海拔梯度增大而降低的趋势。土壤pH值、有效磷、有机碳、海拔对AM真菌的群落分布均产生显著影响,尤以海拔的影响最为显著。研究结果对预测高寒草原微生物的作用与影响,以及高寒草原环境对全球变化的响应等提供了理论依据。     

Effects of concrete properties and nutrients on fungal colonization and fouling

This study describes the fouling of concrete surfaces by diverse fungal genera under controlled laboratory conditions. A circulating flow-through chamber was designed for testing the effects of different concrete compositions and exogenously added nutrients on fungal colonization and fouling. Fungal strains belonging to the genera Alternaria, Cladosporium, Epicoccum, Fusarium, Mucor, Penicillium, Pestalotiopsis, and Trichoderma were cultured directly from visibly fouled concrete structures and used individually and in a mix to inoculate mortar tiles varying in cement composition, supplementary cementitious material additions, water-to-cement ratio, and surface roughness. A strong positive relationship was observed between tile water-to-cement ratio and the amount of biofouling. In addition, cement containing photocatalytic titanium dioxide and exposed to artificial sunlight strongly inhibited fungal colonization and fouling. Mortar tiles coated with form-release oil and incubated with sterile rainwater were also capable of supporting fungal colonization. Our results indicate that the fouling of concrete surfaces by fungi can be influenced by variations in concrete composition variations and available nutrients.     

不同生境黑果枸杞根际与非根际土壤微生物群落多样性

研究典型生境黑果枸杞根际与非根际土壤微生物群落多样性及其与土壤理化性质间的关系,为进一步研究黑果枸杞抗逆性提供理论数据。采集新疆精河县艾比湖地区(EB)盐碱地、乌苏市(WS)路旁荒地、五家渠市(WQ)人工林带的黑果枸杞根际与非根际土壤,利用Illumina-MiSeq高通量测序技术分析细菌和真菌群落组成和多样性。结果表明:根际土壤细菌多样性高于非根际土壤(WQ除外),而根际真菌多样性低于非根际土壤。WQ非根际土壤细菌和真菌多样性均高于EB和WS;根际细菌多样性排序为EBWSWQ,根际真菌多样性排序为WSEBWQ。根际土壤优势细菌门依次是变形菌门、拟杆菌门、放线菌门、酸杆菌门,真菌优势门为子囊菌门、担子菌门。根际土壤细菌变形菌门、拟杆菌门、酸杆菌门的相对丰度高于非根际土壤,而厚壁菌在根际土壤中的丰度显著降低,真菌优势门丰度在根际土和非根际土中的变化趋势因地区而异; Haliea、Gp10、Pelagibius、Microbulbifer、假单胞菌属、Thioprofundum、Deferrisoma是根际土壤细菌优势属;多孢子菌属、支顶孢属、Corollospora、Cochlonema是根际真菌优势属。细菌、真菌优势类群(门、属)的组成以及丰富度存在地区间差异,厚壁菌门在EB地区的丰富度显著高于含盐量较低的WS、WQ;盐碱生境EB中根际土壤嗜盐细菌的丰度高于非盐碱生境(WQ、WS),如盐单胞菌属、动性球菌属、Geminicoccu、Pelagibius、Gracilimonas、Salinimicrobium等。小囊菌属是EB根际真菌的最优势属,Melanoleuca是WQ和WS的最优势属,地孔菌属、Xenobotrytis、Brachyconidiellopsis、多孢子菌属等在EB根际土壤中的丰度显著高于WQ和WS。非盐碱生境(WS和WQ)的微生物群落之间的相似性较高,并且高于与盐碱环境(EB)之间的相似性,表明土壤含盐量对微生物群落组成丰度具有重要的影响。     

DISTRIBUTION OF FUNGI IN EARLY STAGES OF SUCCESSION IN INDIANA DUNE SAND

The most common pattern of succession in the most recently active dunes along the southern shore of Lake Michigan is the formation and stabilization of dunes by marram grass, Ammophila breviligulata, the decline of this population after stabilization and its eventual replacement by little bluestem grass, Andropogon scoparius var. septentrionalis. The previously reported distribution of fungi from the sand at 15 cm below the surface in two adjacent communities which represent these stages has been confirmed and the generality of the distribution established for other similar communities of this region and the Warren Dunes State Park in southwestern Michigan. A characteristic fungal flora was isolated from the sand of the Andropogon communities, and 5 fungal species were found to be part of the flora in every one of the communities investigated. No such characteristic flora could be detected in the Ammophila communities. Monthly samples indicated no seasonal variations in the numbers and composition of the fungal flora. The presence of a characteristic fungal flora in the Andropogon communities and its absence in the Ammophila communities indicates a successional trend from a harsh, unstable environment, low in available mineral and organic matter content, to one more stable and suitable for fungal growth.     

Screening for Ligninolytic Enzyme Production by Diverse Fungi from Tunisia

Summary This work represents the first report on the ability of autochthonous fungi from Tunisia to produce ligninolytic enzymes. Three hundred and fifteen fungal strains were isolated from different Tunisian biotopes. These fungal strains were firstly screened on solid media containing Poly R-478 or ABTS as indicator compounds that enabled the detection of lignin-modifying enzymes as specific color reactions. Of the 315 tested strains, 49 exhibited significant ABTS-oxidation activity expressed within the first week of incubation and only 18 strains decolorized the Poly R-478. Liquid cultivations and laccase, manganese peroxidase and lignin peroxidase activity assays of positive strains confirmed that eight efficient enzyme producers were found in the screening. These strains were attributed to the most closely related species using PCR amplification and sequencing of the internal transcribed spacer ‘ITS’ regions of the ribosomal DNA. The identification results showed fungal genera such as Oxyporus, Stereum and Trichoderma which have been only rarely reported as ligninolytic enzyme producers in the literature. Culture conditions and medium composition were optimized for the laccase producer Trametes trogii CTM 10156. This optimization resulted in high laccase production, 367 times more than in non-optimized conditions and which reached 110 U ml^-1 within 15 days of incubation.     

Occurrence of arbuscular mycorrhizal fungi in bromeliad species from the tropical Atlantic forest biome in Brazil

The mycorrhizal status of epiphytic, rupicolous, and terrestrial bromeliad species from the Brazilian Atlantic Rain Forest has been examined. Roots of 13 species of bromeliads were analyzed for the presence of mycorrhizal structures such as arbuscules, hyphae, and vesicles as well as other fungal structures. Rhizosphere soil was sampled to identify arbuscular mycorrhizal fungal (AMF) species associated only with terrestrial bromeliad species. Most specimens collected were epiphytic bromeliads in the genera Aechmea, Bilbergia, Nidularium, Tillandsia, and Vriesea. Differentiating structures of AMF were found in only three species of bromeliads. The pattern of mycorrhizal colonization was mainly internal, and external mycelium and arbuscules were observed only in the terrestrial Nidularium procerum. Root endophytes with dark brown septate mycelium, thin external hyphae, and Rhizoctonia-like sclerotia were also detected in some root segments. A total of ten spore morphotypes were recovered from the rhizosphere of N. procerum, with Acaulospora mellea, A. foveata, and Glomus sp. being the most common species recovered. Our study demonstrated that most of the epiphytic species are not associated with AMF. We attribute this mainly to the exposed bare root conditions found in epiphytic bromeliads.     

Highlighting patterns of fungal diversity and composition shaped by ocean currents using the East China Sea as a model

How ocean currents shape fungal transport, dispersal and more broadly fungal biogeography remains poorly understood. The East China Sea (ECS) is a complex and dynamic habitat with different water masses blending microbial communities. The internal transcribed spacer 2 region of fungal rDNA was analysed in water and sediment samples directly collected from the coastal (CWM), Kuroshio (KSWM), Taiwan warm (TWM) and the shelf mixed water mass (MWM), coupled with hydrographic properties measurements, to determine how ocean currents impact the fungal community composition. Almost 9k fungal operational taxonomic units (OTUs) spanning six phyla, 25 known classes, 102 orders and 694 genera were obtained. The typical terrestrial and freshwater fungal genus, Byssochlamys, was dominant in the CWM, while increasing abundance of a specific OTU affiliated with Aspergillus was revealed from coastal to open ocean water masses (TWM and KSWM). Compared with water samples, sediment harboured an increased diversity with distinct fungal communities. The proximity of the Yangtze and Qiantang estuaries homogenizes the surface water and sediment communities. A significant influence of ocean currents on community structure was found, which is believed to reduce proportionally the variation explained by environmental parameters at the scale of the total water masses. Dissolved oxygen and depth were identified as the major parameters structuring the fungal community. Our results indicate that passive fungal dispersal driven by ocean currents and river run‐off, in conjunction with the distinct hydrographic conditions of individual water masses, shapes the fungal community composition and distribution pattern in the ECS.     

Effects of weather conditions on selected airborne fungal spores in the southern part of the state of Enugu,Nigeria

A study of airborne fungal spore was carried out at nine locations in the southern part of the state of Enugu, Nigeria, from March 2005 to February 2006. The aim of the study was to ascertain the variations in selected fungal spore types at the sites owing to weather conditions. The variation in airborne fungal spores of 14 taxa was studied using modified Tauber pollen traps including Alternaria, Corynespora, Curvularia, Drechslera type, Endophragmiella, Botryodiplodia, Ganoderma, Gliomastrix, Nigrospora, Pithomyces, Spegazzinia, Sporidesmium, Tetraploa and Ustilago. The frequency of the spore types recorded showed considerable variation. The highest spore counts were recorded in July, June and October. The highest numbers of fungal spores were recorded during the rainy season (June–October) to early dry season (November–December). The peak of occurrence of most selected fungal spore types was July. The highest percentages of fungal spores were documented at the recording stations Mgbowo Junction, UNTH Ituku Ozalla and Oji River Express Junction. Spearman’s correlation analyses were performed for the monthly amounts of the fungal spore types and monthly meteorological factors. The numbers of Curvularia, Nigrospora and Sporidesmium was significantly correlated with relative humidity, while those of Endophragmiella, Pithomyces and Nigrospora were significantly correlated with temperature. A significant correlation was also found between the number of Nigrospora spores and light intensity and Sporidesmium spores and wind velocity. Relative humidity and temperature seem to be the most important weather conditions affecting the frequency of the selected spore types in the atmosphere.     

施氮对森林生态系统AM真菌群落组成及多样性的影响

丛枝菌根（AM）真菌能够和绝大多数陆生植物形成互惠共生体,具有重要的生态功能。在氮（N）沉降日益严重的背景下,越来越多的土壤生态学家开始关注N沉降对AM真菌群落的影响,然而已有研究大多数集中在草地生态系统,对森林生态系统的关注相对较少,而在森林生态系统开展的模拟研究又多采用林下施N的方式,忽略了冠层发生的一系列生态过程,可能无法准确反映真实情形。依托鸡公山野外控制试验平台,采用高通量测序技术就不同施N方式（林下vs林冠）及速率对AM真菌alpha多样性和群落组成的影响进行了连续4 a的监测。试验综合考虑植被、坡向和坡度等因素,采用完全随机区组设计,包括4个区组（重复）,每个区组随机设置5个样方,对应5个不同处理：对照（CK）、林冠施N 25 kg hm^-2 a^-1（CN25）和50 kg hm^-2 a^-1（CN50）、林下施N 25 kg hm^-2 a^-1（UN25）和50 kg hm^-2 a^-1（UN50）。结果发现,在目前的N素添加水平和时间尺度上,施N方式和施N速率对AM真菌的alpha多样性都没有显著影响,二者之间也无交互作用。然而,经过一年的试验处理,施N方式对AM真菌群落组成产生了轻微的影响,而施N速率有极显著的影响,且二者之间存在显著交互作用。当施N速率为25 kg hm^-2 a^-1时,林冠施N和对照相比差异不显著,而林下施N处理AM真菌群落组成与对照相比差异极显著,与林冠施N相比,差异也极显著;当施N速率为50 kg hm^-2 a^-1时,林冠施N与对照处理群落组成有略微差异（P=0.080）,林下施N与林冠施N及对照处理相比AM真菌群落组成均没有显著变化。在接下来的三年中,施N方式和施N速率对AM真菌的群落组成都没有显著影响,二者之间也无显著交互作用。这说明在特定的施N速率和处理时间下,林下施N可能会高估自然N沉降对AM真菌群落组成的影响。随着处理时间的延长,不同处理下AM真菌群落有趋同的趋势,可能是因为AM真菌群落对N沉降产生了适应性。本研究评估了施N方式对森林生态系统AM真菌群落组成与结构的影响,在未来的研究中需要设定更多的N素梯度和更长的时间跨度,才能够更全面的认识N沉降的生态效应。     

Screening for alkaline keratinolytic activity in fungi isolated from soils of the biosphere reserve “Parque Costero del Sur” (Argentina)

A screening was carried out on 69 fungal strains isolated from alkaline-calcareous, neutral and alkaline-sodic soils, as well as from their associated plant material, to determine their ability to grow at alkaline pH. A total of 32 fungi were selected for their ability to produce alkaline keratinase activity in submerged shaken cultures supplemented with soybean meal (SM) and tryptone and on cow hair (CH) under solid state fermentation conditions. Although several fungal strains produced keratinolytic activity on both SM and CH, they differed in the levels detected. Among them, Aspergillus niger, Cladosporium cladosporioides, Metarrhizium anisopliae, Neurospora tetrasperma and Westerdikella dispersa were the best producers, with levels higher than 1.2 U ml⁻¹. Different fungal species are here reported for the first time for their ability to produce keratinolytic activity at alkaline pH.