Invertebrate grazing affects nitrogen partitioning in the saprotrophic fungus Phanerochaete velutina

The heterogeneity of nutrients in forest soils is governed by many biotic and abiotic factors. The significance of nutrient patchiness in determining soil processes remains poorly understood. Some saprotrophic basidiomycete fungi influence nutrient heterogeneity by forming large mycelial networks that enable translocation of nutrients between colonized patches of dead organic matter. The effect of mycophagous soil fauna on these networks and subsequent nutrient redistribution has, however, been little studied. We used a soil microcosm system to investigate the potential effects of a mycophagous collembola, Protaphorura armata, on nutrient transfer within, and nutrient loss from, the mycelium of a saprotrophic basidiomycete fungus, Phanerochaete velutina. A ¹⁵N label, added to central mycelium, was used to track nitrogen movement within the microcosms across 32 days. Although collembola grazing had little impact on δ¹⁵N values, it did alter the partitioning of ¹⁵N between different regions of mycelia. Less ¹⁵N was transferred to new mycelial growth in grazed systems than in ungrazed systems, presumably because collembola reduced fungal growth rate and altered mycelial morphology. Surprisingly, collembola grazing did not increase the mineralization of N from mycelium into the bulk soil. Overall, our results suggest that mycophagous soil fauna can alter nutrient flux and partitioning within fungal mycelium; this has the potential to affect the dynamics and spatial heterogeneity of forest floor nutrients.     

降解玉米秸秆粗纤维担子菌筛选及其应用

从23种担子菌中筛选玉米秸秆粗纤维分解能力强的4菌株,通过二因素随机区组试验对菌株与培养料组合进行比较,并利用海兰商品代蛋用公鸡雏进行了替代部分日粮的饲喂增重试验;对菌化后饲料的营养成分进行分析,并对雏鸡进行饲喂增重试验。结果表明:S-2菌株为降解玉米秸秆粗纤维的最佳菌株;玉米秸秆经该菌固态发酵后粗纤维含量下降了30.5%,而粗蛋白增加了31.3%,粗脂肪提高25%,含有16种氨基酸及钙、磷等矿物质;S-2转化玉米秸秆饲料有可能代替部分配合饲料饲喂非反刍动物。     

Evaluating durability of thermoplastic wood composites against basidiomycetes and development of a suitable test design

Abstract

Wood polymer composites (WPC) consist mainly of wood particles from non-durable softwoods. From experience in service life and laboratory testing it is known that WPC is not fully resistant against biological attack. Concerning durability testing, it is difficult to reach sufficient moisture content for fungal growth in the time frame of testing. Furthermore, the interpretation of test results is difficult, since the mass loss is measured but strength loss might be more important during service life. The relation between mass loss and strength loss is not deeply explored so far. Additionally moisture uptake causes an irreversible strength loss of WPC. Considering these problems a new test method for investigating the resistance of WPC against basidiomycetes is described in prEN 15534-1. In this paper, several test methods were carried out regarding their suitability for durability testing of WPC. The tests included various pre-wetting methods. After durability testing the mass loss and changes in strength and stiffness were evaluated. The results have shown that pre-wetting according to EN 84 is suitable to increase the moisture content. Furthermore strength and stiffness loss is higher than mass loss. The loss in mechanical properties is based on moisture uptake as well as fungal decay.     

Screening for host responses in Acacia to a canker and wilt pathogen,Ceratocystis manginecans

In Vietnam, the productivity of Acacia hybrid (Acacia mangium x A. auriculiformis) plantations is being threatened by an aggressive canker pathogen, Ceratocystis manginecans, and selection for tolerance is the main control strategy. A pot trial was established in Binh Duong province to screen for the host response of nine Acacia genotypes (six Acacia hybrid clones, two A. auriculiformis clones and mixed provenance seedlings of A. mangium) to artificial inoculation with three isolates of C. manginecans. Lesion lengths as measured on the inner bark suggested that the two A. auriculiformis clones were relatively more tolerant to C. manginecans than the A. mangium genotype. In contrast, the lesion lengths of all six Acacia hybrid clones fell between the A. auriculiformis and A. mangium genotypes. The results of this study indicate that among the Acacia hybrid clones, BV10 showed the most tolerance to C. manginecans. Chemical analysis of crude sapwood extracts sampled from the lesion provided some evidence that induced phenolic compounds, particularly tetrahydroxyflavanone and condensed tannins may have a defensive role in the Acacia—C. manginecans pathosystem. However, results were not consistent across individual Acacia hybrid clones and A. mangium genotypes.     

Molecular characterization of fungal endophytic morphospecies isolated from stems and pods of Theobroma cacao

Endophytic fungi were isolated from healthy stems and pods of cacao ( Theobroma cacao ) trees in natural forest ecosystems and agroecosystems in Latin America and West Africa. These fungi were collected for screening as a potential source of biocontrol agents for the basidiomycetous pathogens of cacao in South and Central America, Moniliophthora roreri (frosty pod rot) and Moniliophthora perniciosa (witches' broom). Many of these isolates were morphologically unidentifiable as they failed to form fruiting structures in culture, or only produced arthrosporic stages. Affinities with basidiomycetes were suspected for many of these based on colony morphology. Fifty-nine of these morphologically unidentifiable isolates were selected for molecular identification by DNA extraction and sequence analysis of nuclear ribosomal DNA (rDNA). The large subunit (LSU) was chosen for initial sequencing because this region has been used most often for molecular systematics of basidiomycete fungi, and comprehensive LSU datasets were already available for sequence analyses. Results confirmed that the majority of the isolates tested belonged to the Basidiomycota, particularly to corticoid and polyporoid taxa. With LSU data alone, identification of the isolates was resolved at varying taxonomic levels (all to order, most to family, and many to genus). Some of the isolates came from rarely isolated genera, such as Byssomerulius , whilst the most commonly isolated basidiomycetous endophyte was a member of the cosmopolitan genus Coprinellus (Agaricales). The role of these fungi within the host and their potential as biological control agents are discussed.     

山西吕梁山大红菇的学名考证

采用ITS分子片段分析方法,确认了山西吕梁山南部五鹿山出产的红色蘑菇为血红菇(Russula sanguinaria)。血红菇为山西新记录种,于夏秋季节在油松林内大量发生,为现阶段当地油松林的优势外生菌根菌物种。中国文献记载可食用。     

Transformation of C-labelled lignin and humic substances in forest soil by the saprobic basidiomycetes Gymnopus erythropus and Hypholoma fasciculare

Litter decomposing basidiomycetous fungi produce ligninolytic oxidases and peroxidases which are involved in the transformation of lignin, as well as humic and fulvic acids. The aim of this work was to evaluate their importance in lignin transformation in forest litter. Two litter decomposing basidiomycete species differing in their abilities to degrade lignin - Hypholoma fasciculare, and Gymnopus erythropus - were cultured on sterile or non-sterile oak litter and their transformation of a ¹⁴C-labelled synthetic lignin (dehydrogenation polymer ¹⁴C-DHP) was compared with that of the indigenous litter microflora. Both in sterile and non-sterile litter, colonisation by basidiomycetes led to higher titres of lignocellulose-degrading enzymes, in particular of laccase and Mn-peroxidase (MnP). The titres of the latter were 6 to 40-fold increased in the presence of basidiomycetes compared to non-sterile litter. During 10 weeks, G. erythropus mineralised over 31% of ¹⁴C-DHP in sterile litter and 23% in non-sterile litter compared to 14% in the non-sterile control. Lignin mineralization by H. fasciculare was comparable to the non-sterile control, 12% in sterile litter and 16% in the non-sterile litter. The largest part of ¹⁴C from ¹⁴C-DHP was transformed into humic compounds during litter treatment with both fungi as well as in the control. In addition to the fast lignin mineralization, microcosms containing G. erythropus also showed a lower final content of unaltered lignin and 23-28% of the lignin was converted into water-soluble compounds with relatively low molecular mass (<5 kDa). Both G. erythropus and H. fasciculare were also able to further mineralise humic compounds. During a 10-week fungal treatment of an artificial ¹⁴C-humic acid (¹⁴C-HA) supplemented to the natural humic material of a forest soil, the fungi mineralised 42% and 19% of the labelled material, respectively, under sterile conditions. The ¹⁴C-HA mineralization by introduced basidiomycetes in microcosms containing non-sterile humic material, however, did not significantly differ from that of a non-sterile control and was around 12%. Altogether the results show that saprobic basidiomycetes can considerably differ in their rates of lignin and humic substance conversion. Furthermore, lignin degradation in forest soil can rather slow down by interspecific competition than it is accelerated by cooperation of different microorganisms occupying specific nutritional niches. Therefore, the overall contribution of saprobic basidiomycetes depends on their particular eco-physiological status and the competitive pressure, and may be often lower than initially expected. Significant lignin transformation including partial mineralization is seemingly not exclusively dependent on exceptional high titres of ligninolytic enzymes but also on so far unknown factors. Higher endocellulase production and subsequent weight loss was found in microcosms where saprobic basidiomycetes were combined with indigenous microbes. Potentially, lignin degradation by the basidiomycetes may have increased cellulose availability to the indigenous microbes.     

Factors of species-specific detectability in conservation assessments of poorly studied taxa: The case of polypore fungi

The differing detectability of species is an important issue in conservation assessments, notably for interpreting the heterogeneous datasets of species-rich, poorly-studied species groups. However, detectability has not been explicitly considered in such cases so far. The aim of this study was to extract the main factors of detectability for polypore fungi. I explored interspecific variation in the number of fruit-body records in Estonia (13 210 records of 212 species) in relation to five potential factors of their detectability: longevity, size, bright colour, typical microhabitat and field identificability. The longevity and identificability of fruit-bodies emerged as major factors, with their extreme combinations revealing a variation of over two orders of magnitude in the number of records. The possibility that these factors are related to true abundances in the field cannot be rejected, but it is unlikely. The approach enables us to formally distinguish rarely observed but poorly detectable species that should be classified as Data Deficient in the red-listing process; it can also be used for recognizing well detectable indicator and focal species for conservation management.     

Production of lignocellulose-degrading enzymes and degradation of leaf litter by saprotrophic basidiomycetes isolated from a Quercus petraea forest

Due to the production of lignocellulose-degrading enzymes, saprotrophic basidiomycetes can significantly contribute to the turnover of soil organic matter. The production of lignin- and polysaccharide-degrading enzymes and changes of the chemical composition of litter were studied with three isolates from a Quercus petraea forest. These isolates were capable of fresh litter degradation and were identified as Gymnopus sp., Hypholoma fasciculare and Rhodocollybia butyracea. Within 12 weeks of incubation, H. fasciculare decomposed 23%, R. butyracea 32% and Gymnopus sp. 38% of the substrate dry mass. All fungi produced laccase and Mn-peroxidase (MnP) and none of them produced lignin peroxidase or other Mn-independent peroxidases. There was a clear distinction in the enzyme production pattern between R. butyracea or H. fasciculare compared to Gymnopus sp. The two former species caused the fastest mass loss during the initial phase of litter degradation, accompanied by the temporary production of laccase (and MnP in H. fasciculare) and also high production of hydrolytic enzymes that later decreased. In contrast, Gymnopus sp. showed a stable rate of litter mass loss over the whole incubation period with a later onset of ligninolytic enzyme production and a longer lasting production of both lignin and cellulose-degrading enzymes. The activity of endo-cleaving polysaccharide hydrolases in this fungus was relatively low but it produced the most cellobiose hydrolase. All fungi decreased the C/N ratio of the litter from 24 to 15-19 and Gymnopus sp. also caused a substantial decrease in the lignin content. Analytical pyrolysis mass spectrometry of litter decomposed by this fungus showed changes in the litter composition similar to those caused by white-rot fungi during wood decay. These changes were less pronounced in the case of H. fasciculare and R. butyracea. All fungi also changed the mean masses of humic acid and fulvic acid fractions isolated from degraded litter. The humic acid fraction after degradation by all three fungi contained more lignin and less carbohydrates. Compared to the decomposition by saprotrophic basidiomycetes, litter degradation in situ on the site of fungal isolation resulted in the relative enrichment of lignin and differences in lignin composition revealed by analytical pyrolysis. It can most probably be explained by the participation of non-basidiomycetous fungi and bacteria during natural litter decomposition.