木材腐朽菌在森林生态系统中的功能

木材腐朽菌是森林生态系统的重要组成部分,在森林生态系统中起着极为重要的降解还原作用,主要包括担子菌门非褶菌目、子囊菌门盘菌纲和半知菌类的部分真菌,能全部或部分降解木材中的木质素、纤维素和半纤维素,其降解机制有3种：白色腐朽、褐色腐朽和软腐朽．木材腐朽菌与生态系统中其它生物关系密切,为很多昆虫、鸟类提供营养,有些昆虫也能使木腐菌得到传播．保护木材腐朽菌的生物多样性是保护森林生态系统、维护生态系统健康的重要因素．     

Ascomycetes on Myrica gale in Sweden

The Ascomycete flora on Myrica gale has been investigated, mainly on the basis of Swedish material. It is found to be largely host specific. Four Discomycetes and nine Pyrenomycetes s. lat. are recorded as true, ± exclusive Myrica fungi; ten plurivorous Pyrenomycetes have occasionally been met with. The mycoflora on Myrica gale seems to be of a rather recent origin, composed of fairly modern species. Six new names are published: Gibbera gemmarum sp. nov., G. minutissima sp. nov., Melanomma myricae sp. nov., Semisphaeria sigmundii gen. nov. et sp. nov., Stomiopeltis myricae sp. nov., and Trichopezizella myricae comb. nov.     

Wood decay under the microscope

Many aspects of the interactions between host wood structure and fungal activity can be revealed by high resolution light microscopy, and this technique has provided much of the information discussed here. A wide range of different types of decay can result from permutations of host species, fungal species and conditions within wood. Within this spectrum, three main types are commonly recognised: brown rot, white rot and soft rot. The present review explores parts of the range of variation that each of these encompasses and emphasizes that degradation modes appear to reflect a co-evolutionary adaptation of decay fungi to different wood species or the lignin composition within more primitive and advanced wood cell types. One objective of this review is to provide evidence that the terms brown rot, white rot and soft rot may not be obsolete, but rigid definitions for fungi that are placed into these categories may be less appropriate than thought previously. Detailed knowledge of decomposition processes does not only aid prognosis of decay development in living trees for hazard assessment but also allows the identification of wood decay fungi that can be used for biotechnology processes in the wood industry. In contrast to bacteria or commercial enzymes, hyphae can completely ramify through solid wood. In this review evidence is provided that wood decay fungi can effectively induce permeability changes in gymnospermous heartwood or can be applied to facilitate the identification of tree rings in diffuse porous wood of angiosperms. The specificity of their enzymes and the mild conditions under which degradation proceeds is partly detrimental for trees, but also make wood decay fungi potentially efficient biotechnological tools.     

Deterioration,decay and identification of fungi isolated from wooden structures at the Humberstone and Santa Laura saltpeter works: A world heritage site in Chile

The use of wood in construction has been part of mankind's history but wood placed into the environment is affected by biotic and abiotic agents and is degraded over time. Even in extreme environments, such as dry desert sites, deterioration of wood can take place. One site located in the Atacama Desert in northern Chile is the Humberstone and Santa Laura saltpeter works where offices and other structures were built of wood. Founded in 1872, the Humberstone and Santa Laura Saltpeter Works was designated a UNESCO World Heritage Site in 2005 for its historic significance. Since significant deterioration in the wooden buildings has taken place, investigations were initiated to better understand the degradation underway so conservation efforts to protect the historic buildings can be developed. The objectives of this study were to identify the type of deterioration and decay taking place and to isolate and identify fungi from wood samples of structural elements at both sites. Samples of deteriorated wood showed extensive degradation that resulted in a defibration of the wood. The middle lamella between cells was degraded and remaining secondary walls separated due to high concentrations of salts. This resulted in a serious corrosion of the exterior layers of wood cells. Although high salts inhibit fungi, many different fungi were isolated. Sequencing of the ITS region of the rDNA was used and fungi were identified as Penicillium chrysogenum, Engyodontium album, Eupenicillium tropicum, Penicillium digitatum, Pseudotaeniolina globosa, Cladosporium phaenocomae, Aureobasidium pullulans, Penicillium virgatum, Coprinopsis sp. and Phanerochaete sordida. Several of these fungi appear to be halophilic.     

Indoor wood-decay basidiomycetes: damage,causal fungi,physiology, identification and characterization,prevention and control

Indoor wood-decay fungi cause considerable economical damage. Most of the structural damage to the indoors of buildings in Europe and North America is caused by brown-rot fungi that degrade conifer wood; white-rot fungi, which preferentially attack hardwoods, are less common. This review covers the approximately 80 basidiomycetes that commonly occur in buildings. Emphasis was placed on Serpula lacrymans, which is the most common indoor basidiomycete in central Europe. Meruliporia incrassata, the North American pendant to S. lacrymans, has also received considerable attention. In terms of indoor wood decay, moisture and temperature are the most important influences. Wood samples with a low moisture content can be degraded. High temperatures as an alternative control measure do not kill mycelia, with some species surviving in wood samples in the form of heat-resistant arthrospores at temperatures as high 95°C. For refurbishment and scientific purposes, the identity of the causal species should be known. More recently, several molecular techniques have been used to identify fungi; these results are often conflicting with those obtained by other, earlier applied methods. Sequencing of the internal transcribed spacers (ITS) of the rDNA is currently the best molecular tool. Among the other methods available, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) has also been shown to be able to distinguish closely related sister taxa. For further characterization of indoor basidiomycetes, the complete sequences of the 18S, 28S rDNA and the intergenic spacers with the included 5S rDNA have been acquired for some species. If current projects involving whole funal genome sequencing are not taken into account, Antrodia vaillantii is the first basidiomycete for which the complete rDNA sequence has been deposited. The review closes with fundamentals on the prevention and control of indoor wood decay. An erratum to this article can be found at     

The role of novel forest ecosystems in the conservation of wood‐inhabiting fungi in boreal broadleaved forests

The increasing human impact on the earth's biosphere is inflicting changes at all spatial scales. As well as deterioration and fragmentation of natural biological systems, these changes also led to other, unprecedented effects and emergence of novel habitats. In boreal zone, intensive forest management has negatively impacted a multitude of deadwood‐associated species. This is especially alarming given the important role wood‐inhabiting fungi have in the natural decay processes. In the boreal zone, natural broad‐leaved‐dominated, herb‐rich forests are threatened habitats which have high wood‐inhabiting fungal species richness. Fungal diversity in other broadleaved forest habitat types is poorly known. Traditional wood pastures and man‐made afforested fields are novel habitats that could potentially be important for wood‐inhabiting fungi. This study compares species richness and fungal community composition across the aforementioned habitat types, based on data collected for wood‐inhabiting fungi occupying all deadwood diameter fractions. Corticioid and polyporoid fungi were surveyed from 67 130 deadwood particles in four natural herb‐rich forests, four birch‐dominated wood pastures, and four birch‐dominated afforested field sites in central Finland. As predicted, natural herb‐rich forests were the most species‐rich habitat. However, afforested fields also had considerably higher overall species richness than wood pastures. Many rare or rarely collected species were detected in each forest type. Finally, fungal community composition showed some divergence not only among the different habitat types, but also among deadwood diameter fractions. Synthesis and applications: In order to maintain biodiversity at both local and regional scales, conserving threatened natural habitat types and managing traditional landscapes is essential. Man‐made secondary woody habitats could provide the necessary resources and serve as surrogate habitats for many broadleaved deadwood‐associated species, and thus complement the existing conservation network of natural forests.     

The effect of α-aminoisobutyric acid on wood decay and wood spoilage fungi

The amino acid analogue α-aminoisobutyric acid (AIB) decreased linear extension growth in fifteen out of sixteen wood decay and wood spoilage fungi. In Serpula lacrimans inhibition of extension growth by AIB was accompanied by an increase in the frequency with which the hyphae of the fungus initiated branches. AIB was shown to have a preservative effect against Lentinus lepideus, Serpula lacrimans and Pleurotus ostreatus when wood blocks were impregnated with this chemical prior to challenge by cultures of these fungi. The effectiveness of this compound in limiting growth in a large number of different fungi suggests that competitive inhibitors of nitrogen uptake and metabolism could be used to control fungi which decay wood and similar materials, and may also have wider applications.     

Competition between two wood-degrading fungi with distinct influences on residues

Many wood-degrading fungi colonize specific types of forest trees, but often lack wood specificity in pure culture. This suggests that wood type affects competition among fungi and indirectly influences the soil residues generated. While assessing wood residues is an established science, linking this information to dominant fungal colonizers has proven to be difficult. In the studies presented here, we used isolate-specific quantitative PCR to quantify competitive success between two distinct fungi, Gloeophyllum trabeum and Irpex lacteus, brown and white rot fungi, respectively, colonizing three wood types (birch, pine, oak). Ergosterol (fungal biomass), fungal species-specific DNA copy numbers, mass loss, pH, carbon fractions, and alkali solubility were determined 3 and 8 weeks postinoculation from replicate wood sections. Quantitative PCR analyses indicated that I. lacteus consistently outcompeted G. trabeum, by several orders of magnitude, on all wood types. Consequently, wood residues exhibited distinct characteristics of white rot. Our results show that competitive interactions between fungal species can influence colonization success, and that this can have significant consequences on the outcomes of wood decomposition.     

The GSTome Reflects the Chemical Environment of White-Rot Fungi

White-rot fungi possess the unique ability to degrade and mineralize all the different components of wood. In other respects, wood durability, among other factors, is due to the presence of extractives that are potential antimicrobial molecules. To cope with these molecules, wood decay fungi have developed a complex detoxification network including glutathione transferases (GST). The interactions between GSTs from two white-rot fungi, Trametes versicolor and Phanerochaete chrysosporium, and an environmental library of wood extracts have been studied. The results demonstrate that the specificity of these interactions is closely related to the chemical composition of the extracts in accordance with the tree species and their localization inside the wood (sapwood vs heartwood vs knotwood). These data suggest that the fungal GSTome could reflect the chemical environment encountered by these fungi during wood degradation and could be a way to study their adaptation to their way of life.     

Relationships among wood‐boring beetles,fungi, and the decomposition of forest biomass

A prevailing paradigm in forest ecology is that wood‐boring beetles facilitate wood decay and carbon cycling, but empirical tests have yielded mixed results. We experimentally determined the effects of wood borers on fungal community assembly and wood decay within pine trunks in the southeastern United States. Pine trunks were made either beetle‐accessible or inaccessible. Fungal communities were compared using culturing and high‐throughput amplicon sequencing (HTAS) of DNA and RNA. Prior to beetle infestation, living pines had diverse fungal endophyte communities. Endophytes were displaced by beetle‐associated fungi in beetle‐accessible trees, whereas some endophytes persisted as saprotrophs in beetle‐excluded trees. Beetles increased fungal diversity several fold. Over forty taxa of Ascomycota were significantly associated with beetles, but beetles were not consistently associated with any known wood‐decaying fungi. Instead, increasing ambrosia beetle infestations caused reduced decay, consistent with previous in vitro experiments that showed beetle‐associated fungi reduce decay rates by competing with decay fungi. No effect of bark‐inhabiting beetles on decay was detected. Platypodines carried significantly more fungal taxa than scolytines. Molecular results were validated by synthetic and biological mock communities and were consistent across methodologies. RNA sequencing confirmed that beetle‐associated fungi were biologically active in the wood. Metabarcode sequencing of the LSU/28S marker recovered important fungal symbionts that were missed by ITS2, though community‐level effects were similar between markers. In contrast to the current paradigm, our results indicate ambrosia beetles introduce diverse fungal communities that do not extensively decay wood, but instead reduce decay rates by competing with wood decay fungi.     

Studies of growth conditions in wood for three white-rot fungi and their cellulaseless mutants

White-rot fungi, which have the ability to degrade all the wood components including lignin, are of great interest in biotechnological processes based on wood and other lignocellulosic materials. It was demonstrated earlier that enough lignin can be degraded to cause a decrease in the energy demand for production of thermomechanical pulp if wood chips are pretreated by cellulaseless mutants of white-rot fungi. This paper concerns the growth conditions in wood for three white-rot fungi and their cellulaseless mutants in order to determine optimal conditions for such pretreatment processes. The pH and temperature optima have been determined as well as the growth rate in wood. The results show that the growth rate in wood. at least for Cel 44 (a cellulaseless mutant of Sporotrichum pulverulentum), is not the rate-limiting step in delignification. From different mixtures of urea and NH₄H₂PO₄ the optimal nitrogen source was determined for the mutants. The optimal C/N ratio was found to vary between 160/1 and 400/1. It is suggested that the lower the C/N ratio, the faster the growth. It was also demonstrated that both water- and acetone-extractable substances in wood supported the growth of cellulaseless mutants. When some glucose was added to the wood, the weight loss caused by Cel 44 increased. All these observations support earlier findings that lignin in wood cannot be degraded by white-rot fungi unless a more easily metabolizable carbon source is used simultaneously.     

Wood stimulates the demethoxylation of [O14CH3]-labeled lignin model compounds by the white-rot fungi Phanerochaete chrysosporium and Phlebia radiata

Mineralization of polymeric wood lignin and its substructures is a result of complex reactions involving oxidizing and reducing enzymes and radicals. The degradation of methoxyl groups is an essential part of this process. The presence of wood greatly stimulates the demethoxylation of a non-phenolic lignin model compound (a [O¹⁴CH₃]-labeled β-O-4 dimer) by the lignin-degrading white-rot fungi Phlebia radiata and Phanerochaete chrysosporium. When grown on wood, both fungi produced up to 47 and 40% ¹⁴CO₂ of the applied ¹⁴C activity, respectively, under air and oxygen in 8 weeks. Without wood, the demethoxylation of the dimer by both fungi was lower, varying between 0.5 and 35%. Addition of nutrient nitrogen together with glucose decreased demethoxylation when the fungi were grown on spruce wood under air. Because the evolution of ¹⁴CO₂ in the absence of wood was poor, the fungi may have preferably used wood as a carbon and nitrogen source. The amount of fungal mycelium, as determined by the ergosterol assay, did not show connection to demethoxylation. P. radiata also showed a high demethoxylation of [O¹⁴CH₃]-labeled vanillic acid in the presence of birch wood. The degradation of lignin and lignin-related substances should be studied in the presence of wood, the natural substrate for white-rot fungi.     

Species richness and substrate specificity of lignicolous fungi in the canopy of a temperate,mixed deciduous forest

In the more than twenty years in which long-term canopy research has been conducted, mycology has been largely disregarded. Our studies using a construction crane to gain access to the canopy of a forest in Leipzig, Germany are the first long term investigations assessing the diversity and ecology of wood-decaying fungi in a canopy. Thirty-seven individuals of nine different tree species with a large amount of dead wood were selected. Sampling focussed on the four most prominent tree species Acer pseudoplatanus, Fraxinus excelsior, Quercus robur and Tilia cordata. In the years 2002 and 2003 dead wood was collected in different canopy strata. Dead branches were removed and stored for two weeks in open boxes with high humidity to allow growth of fructifications in the laboratory. 118 different taxa were identified (108 species, 77 genera). Corticioid fungi (e.g., of Corticiaceae, Stereaceae, Hymenochaetaceae) dominated the fungal composition with 37 species, pyrenomycetes were present with 18 species. Agaric fungi (Agaricales and Cortinariales) were scarce. Species with minute basidiomes dominated the fungal composition of this systematic group. Agarics with larger sporomes were found only once and were restricted to strongly decayed branches in shaded canopy areas. Concerning species richness and fungal composition the four tree species mentioned above differed remarkably. As expected, many fungi that grew on bark or slightly decayed wood showed a distinct host and substratum specifity. It is noteworthy that fungi which are purportedly to be non-specific were found on single tree species only.     

Resource utilization of wood decomposers: mycelium nuclear phases and host tree species affect wood decomposition by Dacrymycetes

Throughout evolution, wood-decaying fungi have adapted to different woody plants, resulting in wide species diversity. Dacrymycetes, which are brown-rot fungi and include host-recurrent species, are useful for studying fungal adaptation to host trees. When estimating the decay abilities of basidiomycetes, the nuclear phases of the mycelium should be considered, since dikaryons are thought to be more efficient wood-decayers than monokaryons; however, the difference in their physiological performances remains largely untested. In this study, we verified the decay capabilities of dikaryotic and monokaryotic mycelia and tested the hypothesis that the host tree-recurrence of wood-decaying fungi results from their resource utilization in each host wood. The mass loss caused by eight dacrymycetous species from wood of four tree species was investigated in pure cultures. The decomposition ability of dikaryons was greater than that of monokaryons in these experiments. Dikaryotization is expected to raise certain physiological parameters, such as the quantity and variety of wood-decomposing enzymes, thus enhancing the decomposition rate of wood decomposers. The high decomposition ability of dikaryons suggests their superiority over monokaryons to survive under natural conditions. All dacrymycetous strains caused high mass loss from Pinus wood, the main host tree of Dacrymycetes. However, most of the individual tested strains did not cause the greatest mass loss from the wood of their original host group. This result suggested that host-recurrence can be partly explained by resource utilization, but it is likely that other micro-organisms and abiotic factors also affect host-recurrence in the field environment.     

Time course of fungal removal of lipophilic extractives from Eucalyptus globulus wood

Free and esterified sitosterol, the main lipophilic constituents of eucalypt wood extractives, have been associated with the formation of pitch deposits during manufacturing of environmentally-sound paper pulp from Eucalyptus globulus wood. These, and other lipophilic compounds, were analyzed by gas chromatography-mass spectrometry in the course of wood treatments (up to 7 weeks) with four extractive-degrading fungi in order to optimize biotechnological control of pitch deposition in eucalypt pulp (with moderate loss of wood weight). In contrast to commercialized fungi used in pitch control, which are not able to degrade sitosterol, the fungi investigated in this paper produced a rapid decline of both free and esterified sterols in wood. The degradation rate of steroid hydrocarbons and squalene was moderate, and the amount of steroid ketones (probably formed during oxidative degradation of steroids) and triglycerides increased at different stages of wood treatment. Up to 95% removal of total steroids (including free and esterified sterols, steroid ketones and steroid hydrocarbons) by fungi was obtained at the end of wood treatment under the solid-state fermentation conditions used. The most promising results from the point of view of industrial applicability, however, were obtained after 1-2 weeks of treatment with either Phlebia radiata or Poria subvermispora, which enabled 70% steroid removal with a moderate wood weight loss of 1-4%.     

The giant mycoheterotrophic orchid Erythrorchis altissima is associated mainly with a divergent set of wood‐decaying fungi

The climbing orchid Erythrorchis altissima is the largest mycoheterotroph in the world. Although previous in vitro work suggests that E. altissima has a unique symbiosis with wood‐decaying fungi, little is known about how this giant orchid meets its carbon and nutrient demands exclusively via mycorrhizal fungi. In this study, the mycorrhizal fungi of E. altissima were molecularly identified using root samples from 26 individuals. Furthermore, in vitro symbiotic germination with five fungi and stable isotope compositions in five E. altissima at one site were examined. In total, 37 fungal operational taxonomic units (OTUs) belonging to nine orders in Basidiomycota were identified from the orchid roots. Most of the fungal OTUs were wood‐decaying fungi, but underground roots had ectomycorrhizal Russula. Two fungal isolates from mycorrhizal roots induced seed germination and subsequent seedling development in vitro. Measurement of carbon and nitrogen stable isotope abundances revealed that E. altissima is a full mycoheterotroph whose carbon originates mainly from wood‐decaying fungi. All of the results show that E. altissima is associated with a wide range of wood‐ and soil‐inhabiting fungi, the majority of which are wood‐decaying taxa. This generalist association enables E. altissima to access a large carbon pool in woody debris and has been key to the evolution of such a large mycoheterotroph.     

Selective Degradation of Wood Components by White-Rot Fungi

In order to find naturally occurring white-rot fungi which preferentially degrade lignin. 25 different species of such fungi were cultivated on pine wood blocks and on kraft lignin agar plates with and without cellulose. Due to differences in phenol oxidase reactions on the kraft lignin agar plates, the 25 fungi could be divided into two groups, 1 and 2, which also differed in other properties. The three Group I fungi Sporotrichum pulverulentum, Phanerochaete sp. L1 and Polyporus dichrous produced high levels of endo-l,4-β-glucanase and cellobiose:quinone oxidoreductase in shaking cellulose flasks and a low level of phenol oxidase in standing wood meal flasks, The four fungi Merulius tremellosus, Phlebia radiata, Pycuoporus cinnabarinus and Pleurotus ostreatus from Group 2, on the other hand, produced low levels of endo-1,4-β-glucanase and cellobiose:.quinone oxidoreductase in the cellulose. flasks and a high level of phenol oxidase in the wood meal flasks. Analyses of pine wood blocks degraded by the above-mentioned fungi in the presence of either malt extract, asparagine or NH₄H₂PO₄ revealed that malt extract gave good lignin degradation. In the presence of this nutrient source. P. cinnabarinus, at 3.4% weight loss, even degraded 12.5% lignin without loss of cellulose or mannan. No common degradation pattern was, however, obtained using mall extract, asparagine or NH₄H₂PO₄, It is suggested that while-rot fungi, which preferentially degrade lignin, may be found among Group 2 fungi producing large amounts of phenol oxidases.     

木材上的微生物类群对木材的分解及其演替规律

论述了木材上的微生物类群以及各类群在木材生物分解过程中的演替规律 ,并解释了活立木心材能够发生腐朽的原因。结果表明 :能够生长在木材上的微生物类群有木材腐朽菌、木材软腐菌、木材变色菌、污染性霉菌、细菌、放线菌等多种。这些微生物类群共同合作完成对复杂的木质有机物质的生物分解。它们按一定次序进行作用 ,在木材生物分解的不同时期显示出明显的菌种协调与演替规律。一般情况是细菌、一些半知菌、接合菌和子囊菌等先驱微生物首先侵入 ,然后草本对策的木材腐朽菌开始出现 ,最后由竞争对策或忍耐对策的木腐菌取代草本对策的木腐菌 ,这时木材的分解过程就进入稳定的发展阶段 ,最后使木材分解或腐朽。木材腐朽最终是腐殖化阶段 ,这时微生物群落被土壤习居菌如毛霉、青霉、木霉、镰刀菌及细菌与放线菌等所取代。     

Lignicolous freshwater fungi along a north–south latitudinal gradient in the Asian/Australian region; can we predict the impact of global warming on biodiversity and function?

Fungi play a key role in decomposition of submerged wood in streams, breaking down lignocelluloses and releasing nutrients, and are important in ecosystem functioning. These wood decay fungi are known as freshwater lignicolous fungi and are usually studied by collecting submerged woody litter, followed by incubation in a moist chamber. This review explains what are freshwater lignicolous fungi, their decay mechanisms, roles and physiological attributes. Asian/Australasian lignicolous freshwater fungi have been relatively well-surveyed and enable an account of their distribution along a latitudinal transect. Unlike freshwater leaf-dwelling fungi their diversity in water bodies is greater towards the Equator which suggests they are important for decaying submerged wood in the tropics. Riparian vegetation, disturbances such as pollution, streams drying and study methods, may all affect the diversity of freshwater lignicolous fungi, however, the overall trend is a higher diversity in the tropics and subtropics. Climate changes together with increasing deposition of woody debris from human activities, and alteration of environmental factors (such as water pollution, and dam building) will impact freshwater lignicolous fungi. Changing diversity, structure and activities of freshwater fungal communities can be expected, which will significantly impact on aquatic ecosystems, particularly on nutrient and carbon cycles. There is a great opportunity to monitor changes in freshwater fungi communities along latitudinal (north to south) and habitat gradients (from human disturbed to natural habitats), and study ecological thresholds and consequences of such changes, particularly its feedback on nutrient and carbon cycles in freshwater systems.