多裂骆驼蓬提取液的抑菌杀虫作用研究

多裂骆驼蓬(Peganum multisectum Bobr)系蒺藜科的一种多年生草本植物,其种子的乙醇提取物对供试的3种植物病菌有较好的抑菌活性。其中对小麦锈菌抑制活性最显著,其孢子的校正抑制率达78％。对蚜虫的室内毒力测定发现对桃粉蚜(Appeug schwartzi Borner)、桃蚜(Myzus persicae)、麦二叉蚜(Schizaphis gay-minun Rondin)有明显的触杀活性。     

Competition with filamentous fungi and its implication for a gregarious lifestyle in insects living on ephemeral resources

Abstract. 1. Recent studies have demonstrated the existence of positive density dependence in the survival and development of Drosophila (the so‐called Allee effect); however the underlying mechanisms of such Allee effects have remained elusive. Competition with filamentous fungi have often been suggested to be involved in causing high mortality at low larval density, but it has not yet been explicitly tested if the well known spatial aggregation of insect eggs yields a fitness benefit for the developing larvae in the presence of noxious moulds. 2. Using Drosophila melanogaster, the present study tested whether larval survival is greater in aggregations when confronted with various combinations of three representative mould species (Aspergillus, Alternaria, and Penicillium) and a head start for fungal development. 3. High rates of fungal‐dependent mortality and significant positive density‐dependent larval survival (i.e. Allee effects) were observed when larvae were confronted with food resources containing established colonies of Aspergillus or Alternaria. Neither the simultaneous transfer of Aspergillus or Alternaria spores with larvae to food patches nor food infections with Penicillium affected insect larval development. 4. Significant correlations between mould growth and larval survival could be identified, although the patterns that emerged were shown to be inconsistent when the effects were compared between fungal species and fungal priority. Because mould growth only partly explained larval survival, the influence of other fungal‐borne factors, e.g. mycotoxins, needs to be elucidated in order to understand the mechanistic basis of insect–mould interactions. 5. These results are the first to argue convincingly for moulds being involved in mediating Allee effects for insects on ephemeral resources; however they also demonstrate an unexpected diversity in insect–mould interactions. Considering this diversity may be important in understanding insect spatial ecology.     

Effects of Nutrient Enrichment on Decomposition and Fungal Colonization of Sweet Chestnut Leaves in an Iberian Stream (Central Portugal)

This study assessed the effect of nutrient enrichment on rates of decomposition, ergosterol concentrations (as a measure of fungal biomass), and rates of fungal sporulation of sweet chestnut (Castanea sativa Miller) leaves in a 3rd order stream (Central Portugal), with medium to high background values of nutrients. Coarse and fine mesh leaf bags were attached to nutrient diffusing substrata containing NaNO₃, KH₂PO₄, both nutrients, or no additions. Leaf breakdown rates were similar in the four treatments and in the two mesh sizes (k=−0.0155 to −0.0219 day⁻¹). Phosphorus content of P or N + P enriched leaves was higher than in the other treatments after 28 days, but there were no differences in N concentrations. Ergosterol concentrations associated with decomposing leaves were similar among treatments. The peak sporulation rates of aquatic hyphomycetes were stimulated by the addition of N + P and N but not by P alone. Results from the experiment provide evidence that leaf breakdown in the study stream, as a model for streams with naturally medium to high level of nutrients, was not nutrient-limited, and that fungal reproductive activity was limited by dissolved N but not by dissolved P in stream water.     

Toward resolving family-level relationships in rust fungi (Uredinales)

Rust fungi (Basidiomycota, Uredinales) consist of more than 7000 species of obligate plant pathogens that possess some of the most complex life cycles in the Eumycota. Traditionally, a limited number of synapomorphic characters and incomplete life-cycle and host-specificity data have hampered phylogenetic inference within the Uredinales. The application of modern molecular characters to rust systematics has been limited, and current contradictions, especially in the deeper nodes, have not yet been resolved. In this study, two nuclear rDNA genes (18S and 28S) were examined across the breadth of the Uredinales to resolve some systematic conflicts and provide a framework for further studies of the group. Three suborders of rusts are recovered. Of the 13 rust families most widely accepted, 8 are supported in full or in part (Coleosporiaceae, Melampsoraceae, Mikronegeriaceae, Phakopsoraceae p.p., Phragmidiaceae, Pileolariaceae, Pucciniaceae, Raveneliaceae), 3 are redundant (Cronartiaceae, Pucciniastraceae, Pucciniosiraceae), and the status of 2 (Chaconiaceae, Uropyxidaceae) could not be resolved. The Mikronegeriaceae and Caeoma torreyae are the most basal rusts sampled. It is concluded that morphology alone is a poor predictor of rust relationships at most levels. Host selection, on the other hand, has played a significant role in rust evolution. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.     

An unstructured model for studies on phenanthrene bioconversion by filamentous fungus Cunninghamella elegans

An unstructured model for phenanthrene bioconversion by filamentous fungus Cunnighamella elegans in stirred tank batch bioreactors was proposed. It was observed that the process of phenanthrene bioconversion is strictly associated with exponential growth of biomass. Therefore, a Monod-type, with Contois term, unstructured model could be applied to describe the process mathematically. The inhibition of biomass growth due to high concentrations of phenanthrene present in the medium was taken into account in the form of Yerusalimski's uncompetitive inhibition term.     

Purification and Characterization of Fungal Poly(3-hydroxybutyrate) Depolymerase from Paecilomyces lilacinus F4-5 and Enzymatic Degradation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Film

Summary Poly(3-hydroxybutyrate) [P(3HB)] depolymerase was purified from a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)]-degrading fungus, Paecilomyces lilacinus F4-5 by hydrophobic and ion exchange column chromatography, and showed a molecular mass of 45 kDa. The optimum temperature and pH of the P(3HB) depolymerase were 50 °C and 7.0, respectively. The enzyme was stable for at least 30 min at temperatures below 40 °C, while the activity abruptly decreased over 55 °C. Enzymatic P(3HB-co-3HV) degradation showed a similar degradation pattern to that of film overlaid by fungal hyphae. It reflects that the fungal degradation of P(3HB-co-3HV) in soil is mainly caused by extracellular depolymerases.     

白腐菌对培养环境pH的调节及其产漆酶的相关性

研究了不同种属白腐菌多孔菌属C1(Polyporussp.)、侧耳属B2(Pleurotussp.)、香菇属A3(Lentinusedodes)对培养环境pH的调节,及其与菌株产漆酶状况的相关性。结果表明:3株白腐菌均可调节培养液酸化,培养环境的pH可分别由初始的4.5~5.0持续下降至培养结束时3.0~3.5水平,相应C1、B2、A3三者的漆酶合成与分泌在pH值较高(pH 4.5以上)时均表现较弱(酶活分别处于约1 500、200、50 U/mL以下的水平),在pH 3.2~4.5范围内的不同偏酸性条件下则得到较好表达(最高酶活分别达5 000、340、144 U/mL)。统计学分析指出,白腐菌调节环境pH状况与其产漆酶状况之间存在显著或极显著相关性,但不同白腐菌调节培养环境pH的能力之间并不具有显著性差异。     

丛枝菌根养分吸收和转运机制的研究历史与进展

丛枝菌根真菌(AMF)在土壤生态系统中分布最广且在农业生态系统中作用最大,是颇受研究人员关注的一类菌根真菌。多年来,人们尝试着用各种技术和方法从不同角度、不同层次对AMF与植物的互惠机制进行研究并取得了较大进展。近年来分子技术在该领域得以广泛应用,使得人们对这一共生体的互惠机制有了更为详尽的了解。从营养学角度入手,综述了国内外关于丛枝菌根(AM)真菌对土壤中养分吸收和转运机制的研究进展,并在概括当前AMF促生机制研究热点的基础上对其发展前景作了展望。     

病原真菌感染与TOLL样受体

TOLL样受体(TLR)是参与天然免疫的主要模式识别受体之一,与许多微生物病原体及其产物的病原相关分子模式PAMP结合后通过MyD88依赖性或非依赖性途径启动宿主胞内信号传导途径,引发一系列生物学效应。白色念珠菌表面的特征性糖磷脂甘露聚糖可被TLR2、TLR4识别,诱导前炎性细胞因子的释放及促进中性粒细胞的聚集等来介导宿主的抗真菌免疫反应。烟曲霉则可能利用表型转换(酵母样与菌丝态),通过不同TLRs逃避宿主天然免疫系统的识别。新型隐球菌的多糖荚膜成分葡糖醛氧化甘露聚糖GXM可与TLR2、TLR4、CD14结合,在单核细胞、巨噬细胞对GXM的内化、吞噬中起重要作用,而不是诱导细胞因子的分泌;酿酒酵母胞壁成分酵母多糖则可激活TLR2、TLR6异源二聚体。总之,TLR与真菌配体相互作用的具体机制及其活化后胞内信号传导调控机制的深入研究与分析,对临床真菌病的免疫调节及治疗具有重要意义。