鼓槌石斛的地理分布与菌根真菌区系组成的相关性

本文研究了兰科石斛属鼓槌石斛的地理分布与菌根真菌区系组成的相关性。采用克隆文库技术对云南省西双版纳和临沧市两个地区的8份野生鼓槌石斛根部样品进行了分析。结果表明,共从两个地区的鼓槌石斛根部获得了14个真菌的可操作分类单元（OTU）,主要隶属于胶膜菌科Tulasnellaceae和小纺锤菌目Atractiellales。分析鼓槌石斛对菌根真菌的专一性和偏好性发现,鼓槌石斛对菌根真菌专一性较低,每个植株都能同时与多种菌根真菌共生;不同地理分布的鼓槌石斛菌根真菌类群存在明显差异,两个地区的鼓槌石斛的菌根真菌中只有1个OTU是相同的,其余均不同。说明菌根真菌可能和鼓槌石斛的生态适应存在一定的相关性。     

Relocation,high‐latitude warming and host genetic identity shape the foliar fungal microbiome of poplars

Micro‐organisms associated with plants and animals affect host fitness, shape community structure and influence ecosystem properties. Climate change is expected to influence microbial communities, but their reactions are not well understood. Host‐associated micro‐organisms are influenced by the climate reactions of their hosts, which may undergo range shifts due to climatic niche tracking, or may be actively relocated to mitigate the effects of climate change. We used a common‐garden experiment and rDNA metabarcoding to examine the effect of host relocation and high‐latitude warming on the complex fungal endophytic microbiome associated with leaves of an ecologically dominant boreal forest tree (Populus balsamifera L.). We also considered the potential effects of poplar genetic identity in defining the reactions of the microbiome to the treatments. The relocation of hosts to the north increased the diversity of the microbiome and influenced its structure, with results indicating enemy release from plausible pathogens. High‐latitude warming decreased microbiome diversity in comparison with natural northern conditions. The warming also caused structural changes, which made the fungal communities distinct in comparison with both low‐latitude and high‐latitude natural communities, and increased the abundance of plausible pathogens. The reactions of the microbiome to relocation and warming were strongly dependent on host genetic identity. This suggests that climate change effects on host–microbiome systems may be mediated by the interaction of environmental factors and the population genetic processes of the hosts.     

High concentration of basidiolichens in a single family of agaricoid mushrooms (Basidiomycota: Agaricales: Hygrophoraceae)

The Agaricales is the largest and most diverse order of mushroom-forming Basidiomycota, with over 100 natural groups recognized in recent Fungal Tree of Life studies. Most agarics are either saprotrophic or ectomycorrhizal fungi, but the family Hygrophoraceae is in part characterized by a unique and remarkable diversity of lichenized forms. The most familiar of these is the chlorolichen genus Lichenomphalia, whose phylogenetic position in the Agaricales has been established. Recent limited evidence suggested that Hygrophoraceae also contains cyanolichens in the genus Dictyonema, which indicates a remarkable concentration and diversity of lichen-formers in a single family of agarics. To demonstrate the relationships of lichen-formers to other fungi in the family, we assembled ribosomal sequences from 52 species representing recognized groups within the Hygrophoraceae, among them new sequences representing Acantholichen and most species and forms of Dictyonema. The molecular data were evaluated using parsimony, likelihood, Bayesian, and distance analyses, including coding of ambiguous regions by means of INAASE and ARC, all of which indicate that Dictyonema and Acantholichen form a monophyletic clade derived from the primarily bryophilous genus Arrhenia and sister to the enigmatic Athelia pyriformis, a species unrelated to the Atheliales for which we are proposing a new genus name Eonema. The chlorolichen genus Lichenomphalia may be polyphyletic. Fungi in the Dictyonema-Acantholichen clade are typically tropical, entirely lichenized, and associate with cyanobacterial photobionts. Our data indicate a transition from agaricoid-omphalinoid basidiomes observed in Arrhenia to stereoid-corticioid forms in Dictyonema, and also support a previous suggestion of a connection between loss of clamp connections and lichenization. The diverse basidiome and thallus morphologies and nutritional ecologies of these fungi indicate a remarkable evolutionary flexibility that appears to have developed in part as a consequence of symbiosis.     

Assessment of a model for intron RNA secondary structure relevant to RNA self-splicing--a review

A widespread class of introns is characterized by a particular RNA secondary structure, based upon four conserved nucleotide sequences. Among such "class I" introns are found the majority of introns in fungal mitochondrial genes and the self-splicing intron of the large ribosomal RNA of several species of Tetrahymena. A model of the RNA secondary structure, which must underlie the self-splicing activity, is here evaluated in the light of data on 16 further introns. The main body or "core structure" of the intron always consists of the base-paired regions P3 to P9 with the associated single-stranded loops, with P2 present also in most cases. Two minority sub-classes of core structure occur, one of which is typical of introns in fungal ribosomal RNA. Introns in which the core structure is close to the 5' splice site all have an internal guide sequence (IGS) which can pair with exon sequences adjacent to the 5' and 3' splice sites to align them precisely, as proposed by Davies et al. [Nature 300 (1982) 719-724]. In these cases, the internal guide model allows us to predict correctly the exact location of splice sites. All other introns probably use other mechanisms of alignment. This analysis provides strong support for the RNA splicing model which we have developed.     

Mollusc herbivory influenced by endophytic clavicipitaceous fungal infections in grasses

Clavicipitaceous fungi of the genus Neotyphodium occur widely as mutualistic, systemic, seed‐borne infections in festucoid grasses. Grass infection by these fungi is associated with the presence of a range of secondary metabolites (SM), several of which have been demonstrated to confer to the plant resistance against herbivorous vertebrates and insects. An initial experiment demonstrated that endophytic infection by Neotyphodium can influence the utilisation of grasses by Deroceras, with feeding preferences and impact on plant yields affected differentially by endophytes with different SM profiles. The role of Neotyphodium SM in feeding preferences of Deroceras slugs were then evaluated in artificial diets. Among the indole diterpenoids tested, lolitrem B was demonstrated to reduce feeding, while diets containing paxilline, lolitriol, α‐paxitriol and β‐paxitriol tended to be preferred over that of untreated diet. The pyrrolopyrazine alkaloid peramine had no effect. Among the ergopeptine alkaloids tested in the diets, ergotamine and ergovaline were demonstrated to be phagostimulatory. These results with artificial diets were generally consistent with Deroceras reticulatum preferences among plants of known Neotyphodium endophyte strain and SM profile. Deroceras slugs obtained from sites containing contrasting frequencies of Neotyphodium‐infected grasses, exhibited differential responses to Neotyphodium SM incorporated into artificial diet. This study demonstrates that infection of grasses by different isolates of Neotyphodium endophytes differentially influence herbivory by molluscs, reflecting their SM profile. These results offer an explanation for variable acceptability of grasses to molluscs and their importance in the diet of molluscs in the field reported in previous studies in both natural and agricultural systems. Neotyphodium endophytes potentially offer novel approaches to management of mollusc pests in agricultural gramineous crops.     

Production of cellulase by Aspergillus niger biofilms developed on polyester cloth

AIMS: To compare cellulase production by Aspergillus niger ATCC 10864 biofilms on polyester cloth and freely suspended cultures in shaken flasks and microbioreactors of bubble column type. METHODS AND RESULTS: Both shaken flasks and oxygenated microbioreactors containing 40 ml of production medium were used to compare cellulase secretion by free mycelium and biofilm cultures. Free mycelium cultures grew better in flasks than in microbioreactors producing compact and fluffy pellets, respectively, while the opposite was found for biofilm cultures without any visible change in biofilm morphology. Cellulase activities and volumetric productivities attained by biofilms in flask cultures were 70% higher than that produced by free mycelium cultures and threefold higher when biofilms were grown in microbioreactors. CONCLUSIONS: Fungal biofilms developed on polyester cloth in both flasks and microbioreactors produce higher cellulase yields and volumetric productivities than free mycelium cultures at lower biomass levels. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of the present study are of commercial and biological interest. All productivity parameters revealed that fungal biofilms may be used for the production of cellulase and other proteins in various types of bioreactors. Moreover, they may be used as model systems to study differential gene expression related to cell adhesion.     

The biogeography of Miniopterus bats (Chiroptera: Miniopteridae) from the Comoro Archipelago inferred from mitochondrial DNA

The endemic fauna of the Comoro Archipelago is composed of a mixture of taxa originating from Africa and Madagascar. Bats are the only native land dwelling mammals on this archipelago, but the biogeographical origins for the vast majority of species within this group are ambiguous. We report here genetic analyses based on two mitochondrial DNA markers to infer the origin of Comorian bats belonging to a reputed species complex of Miniopterus that is further distributed across Africa and Madagascar. Phylogenetic reconstructions show that east African M. minor are not closely related to the insular Miniopterus of Madagascar and the Comoros (Grande Comore and Anjouan). The latter cluster into two distinct, monophyletic clades (Clade 1 and Clade 2). Representatives of these clades occur sympatrically both on the Comoros and on Madagascar, and are distinguished by a large genetic distance (K2P: 9.9% for cytochrome b). No haplotypes are shared between any islands, suggesting the absence of contemporary gene flow. Populations of the widespread Clade 1 are furthermore characterized by a significant inter‐island structure (Φ_CT = 0.249), and by high haplotype and nucleotide diversities (h = 0.90–0.98, π = 0.04–0.06). Demographic analyses of Clade 1 suggest secondary contact between two distinct phylogroups (Subclade 1 A and 1B) that reached Grande Comore and Anjouan, and a large, stable population with a long evolutionary history on Madagascar. These results and the current distribution of related lineages suggest that the Comoros were colonized independently at least two or three times by ancestors from Madagascar.     

Chitosan isolation from the chitosan-glucan complex of fungal cell wall using amylolytic enzymes

The chitosan/glucan complex isolated from the mycelia of the fungus, Gongronella butleri USDB 0201 can be cleaved with a heat-stable -amylase at 65 °C for 3 h. This results in the removal of the glucan side chain and gives a chitosan solution with 100 times lower turbidity. It is proposed that chitosan and glucan chains are bound by an (1 to 4) glucosidic bond. Both fungal chitosan and fungal glucan have been purified separately.     

The relationship between airborne pollen and fungal spore concentrations and seasonal pollen allergy symptoms in Cracow in 1997–1999

The investigation of airborne pollen and fungalspore concentrations was carried out in Cracowbetween 1997–1999. For this study thevolumetric method has been employed (Burkard).At the same time the clinical diagnosis ofpollen allergy in 40 patients was obtained onthe basis of an interview, positive skin pricktests with pollen extracts and increasedspecific IgE level. An increase in seasonalallergy symptoms in all patients occurred fromthe middle of May to the middle of August.Eighty eight percent of the patients (35 out of40) were sensitive to Poaceae pollen and about50% of them were additionally sensitive totree and herb pollen excluding grasses. Forpatients with additional allergy to tree pollenthe seasonal symptoms started at the end ofMarch (Betula) while for patients withadditional allergy to herb pollen it wasextended to the middle of September (Artemisia).Five people out of 40 revealed positive skinreactions to Alternaria spores and anincrease in specific IgE level. Positive skinreaction to Cladosporium spores with noincrease in specific IgE level occurred in 2patients. The increase in seasonal allergysymptoms in people sensitive to Alternariaspores noted in July and August could becaused not only by these spores but also byPoaceae pollen.     

Dependence of morphology on agitation intensity in fed-batch cultures of Aspergillus oryzae and its implications for recombinant protein production

We previously reported that, although agitation conditions strongly affected mycelial morphology, such changes did not lead to different levels of recombinant protein production in chemostat cultures of Aspergillus oryzae (Amanullah et al., 1999). To extend this finding to another set of operating conditions, fed-batch fermentations of A. oryzae were conducted at biomass concentrations up to 34 g dry cell weight/L and three agitation speeds (525, 675, and 825 rpm) to give specific power inputs between 1 and 5 kWm(-3). Gas blending was used to control the dissolved oxygen level at 50% of air saturation except at the lowest speed where it fell below 40% after 60-65 h. The effects of agitation intensity on growth, mycelial morphology, hyphal tip activity, and recombinant protein (amyloglucosidase) production in fed-batch cultures were investigated. In the batch phase of the fermentations, biomass concentration, and AMG secretion increased with increasing agitation intensity. If in a run, dissolved oxygen fell below approximately 40% because of inadequate oxygen transfer associated with enhanced viscosity, AMG production ceased. As with the chemostat cultures, even though mycelial morphology was significantly affected by changes in agitation intensity, enzyme titers (AGU/L) under conditions of substrate limited growth and controlled dissolved oxygen of >50% did not follow these changes. Although the measurement of active tips within mycelial clumps was not considered, a dependency of the specific AMG productivity (AGU/g biomass/h) on the percentage of extending tips was found, suggesting that protein secretion may be a bottle-neck in this strain during fed-batch fermentations.