不同银杏内酯对黑曲霉线粒体结构及功能的影响

真菌感染作为威胁人类健康的传染性疾病之一,是普遍的全球性问题。本研究通过在黑曲霉的孢子悬浮液中添加不同浓度的银杏内酯,收集黑曲霉菌丝体,评估黑曲霉线粒体的结构和功能,考察不同银杏内酯B和C对黑曲霉的抗真菌效果。透射电子显微镜扫描发现经银杏内酯B处理后的黑曲霉线粒体表现出明显的空泡化,基质结构被破坏;线粒体三羧酸循环中关键酶琥珀酸脱氢酶和苹果酸脱氢酶活性下降,线粒体膜电位降低,丙二醛和活性氧水平显著升高。研究结果初步揭示了银杏内酯以剂量依赖的方式损坏线粒体膜的完整性,破坏线粒体结构,进一步损害线粒体功能;银杏内酯B的抗黑曲霉效果要显著高于银杏内酯C。     

黑曲霉木质纤维素降解酶基因的可变剪接分析及验证

黑曲霉Aspergillus niger因能够产生大量的木质纤维素降解酶而在木质纤维素资源利用中发挥重要作用。目前,有关黑曲霉基因组中与木质纤维素降解相关的基因是否存在可变剪接的情况尚不清楚。本研究以黑曲霉CBS513.88菌株为研究对象,采用rMATS和ABLas两种方法对黑曲霉在葡萄糖为唯一碳源(G组)和小麦秸秆为唯一碳源(WS组)下的56个木质纤维素降解酶基因的可变剪接事件进行分析,并通过RT-PCR扩增和内含子特异性扩增对3个典型基因的可变剪接体进行了验证。结果表明,ABLas可变剪接分析算法相较于rMATS分析算法更为准确,ABLas分析算法显示G组和WS组共有21个木质纤维素降解酶基因出现了可变剪接,可变剪接类型以内含子保留(IR)为主,占所有可变剪接事件的82.85%。另外,G组和WS组发生可变剪接的木质纤维素降解酶基因也有所不同：G组发生可变剪接的基因为13个,WS组发生可变剪接的基因为14个,两组都发生可变剪接的基因为6个,这表明黑曲霉木质纤维素降解酶基因的可变剪接在不同生长条件下存在差异,另一方面,黑曲霉中众多可变剪接体的存在也为开发新型的木质纤维素降解酶资源提供基础。     

Ergothioneine production with Aspergillus oryzae

To establish a reliable and practical ergothioneine (ERG) supply, we employed fermentative ERG production using Aspergillus oryzae, a fungus used for food production. We heterologously overexpressed the egt-1 and -2 genes of Neurospora crassa in A. oryzae and succeeded in producing ERG (231.0 mg/kg of media, which was 20 times higher than the wild type).

Abbreviations: ERG: ergothioneine; HER: hercynine; Cys-HER: hercynylcysteine-sulfoxide; SAM: S-adenosylmethionine; SAH: S-adenosylhomocysteine; l-His: l-histidine; l-Cys: l-cysteine; LC-ESI-MS: liquid chromatography-electrospray ionization-mass spectrometry     

Production of the plant polyketide curcumin in Aspergillus oryzae: strengthening malonyl-CoA supply for yield improvement

The filamentous fungus Aspergillus oryzae was recently used as a heterologous host for fungal secondary metabolite production. Here, we aimed to produce the plant polyketide curcumin in A. oryzae. Curcumin is synthesized from feruloyl-coenzyme A (CoA) and malonyl-CoA by curcuminoid synthase (CUS). A. oryzae expressing CUS produced curcumin (64 μg/plate) on an agar medium containing feruloyl-N-acetylcysteamine (a feruloyl-CoA analog). To increase curcumin yield, we attempted to strengthen the supply of malonyl-CoA using two approaches: enhancement of the reaction catalyzed by acetyl-CoA carboxylase (ACC), which produces malonyl-CoA from acetyl-CoA, and inactivation of the acetyl-CoA-consuming sterol biosynthesis pathway. Finally, we succeeded in increasing curcumin yield sixfold by the double disruption of snfA and SCAP; SnfA is a homolog of SNF1, which inhibits ACC activity by phosphorylation in Saccharomyces cerevisiae and SCAP is positively related to sterol biosynthesis in Aspergillus terreus. This study provided useful information for heterologous polyketide production in A. oryzae.     

华北地台西缘两个奥陶纪三叶虫新属

Family Raphiophoridae Angelin,1854GenusAbulbaspisgen.nov.Type species Bulbaspis ordosensisLuin Luet al.1976,from the Kli moli Formation(Llanvirn)ofZhuozishan,Wuhai,Inner Mongolia.Diagnosis A raphiophorid genus si milar toAmpyxDal man,1827,but distinguishe…     

Purification and characterization of xylanase from alkali-tolerant Aspergillus fischeri Fxn1

Abstract Alkali-tolerant Aspergillus fischeri Fxn1 produced two extracellular xylanases. The major xylanase ( M _r 31000) was purified to electrophoretic homogeneity by ammonium sulfate precipitation, anion exchange chromatography and preparatory PAGE. Xylose was the major hydrolysis product from oat spelt and birch wood xylans. It was completely free of cellulolytic activities. The optimum pH and temperature were 6.0 and 60 °C, respectively. pH stability ranged from 5 to 9.5 and the t_{1 / 2} at 50 °C was 490 min. It had a K _m of 4.88 mg ml⁻¹and a V _max of 588 μmol min⁻¹ mg⁻¹. The activity was inhibited (95%) by AlCl₃ (10 mM). This enzyme appears to be novel and will be useful for studies on the mechanism of hydrolysis of xylan by xylanolytic enzymes.     

Xylanase production in Aspergillus nidulans: induction and carbon catabolite repression

Abstract The induction of the synthesis of extracellular xylanases was investigated in the fungus Aspergillus nidulans using a number of compounds, including xylans of different origin, monosaccharides, xylooligosaccharides and xylose derivatives. Certain xylans (wheat arabinoxylan, oat spelt xylan, birchwood xylan and 4-O-methyl-D-glucurono-D-xylan) were found to be the most powerful inducers. Also, xylooligosaccharides such as xylobiose, xylotriose and xylotetraose served as inducers, their efficiency being directly related to their chain length. Xylose, on the contrary, was not a true inducer. Of the three endo-β-(1,4)-xylanases secreted by A. nidulans , that of 24 kDa was not under carbon catabolite repression, whereas the other two, of 22 and 34 kDa, were under glucose repression mediated by the creA gene product.     

Biosorption of uranium(VI) by Aspergillus fumigatus

Aspergillus fumigatus removed uranium(VI) very rapidly and reached equilibrium within 1 h of contact of biomass with the aqueous metal solution. Biosorption data fitted to Langmuir model of isotherm and a maximum loading capacity of 423 mg U g^–1 dry wt was obtained. Distribution coefficient as high as 10,000 (mg U g^–1)/(mg U ml^–1) at a residual metal ion concentration of 19 mg l^–1 indicates its usefulness in removal of uranium(VI) from dilute waste streams. Optimum biosorption was seen at pH 5.0 and was independent of temperature (5–50°C ). Initial metal ion concentration significantly influenced uptake capacity which brought down % (w/w) uranium(VI) removal from 90 at 200 mg U l^–1 to 35 at 1000 mg U l^–1. Presence of 0.84 mmol Fe²⁺, Fe³⁺, Ca²⁺ and Zn²⁺ had no effect on uranium(VI) biosorption unlike Al³⁺ (0.84 mM) which was inhibitory.     

An aureobasidin A resistance gene isolated from Aspergillus is a homolog of yeast AUR1, a gene responsible for inositol phosphorylceramide (IPC) synthase activity

The AUR1 gene of Saccharomyces cerevisiae, mutations in which confer resistance to the antibiotic aureobasidin A, is necessary for inositol phosphorylceramide (IPC) synthase activity. We report the molecular cloning and characterization of the Aspergillus nidulans aurA gene, which is homologous to AUR1. A single point mutation in the aurA gene of A. nidulans confers a high level of resistance to aureobasidin A. The A. nidulans aurA gene was used to identify its homologs in other Aspergillus species, including A. fumigatus, A. niger, and A. oryzae. The deduced amino acid sequence of an aurA homolog from the pathogenic fungus A. fumigatus showed 87% identity to that of A. nidulans. The AurA proteins of A. nidulans and A. fumigatus shared common characteristics in primary structure, including sequence, hydropathy profile, and N-glycosylation sites, with their S. cerevisiae, Schizosaccharomyces pombe, and Candida albicans counterparts. These results suggest that the aureobasidin resistance gene is conserved evolutionarily in various fungi. Received: 27 August 1998 / Accepted: 19 November 1998     

Production of a highly glucose-tolerant extracellular β-glucosidase by three Aspergillus strains

Quercetin was the best inducer for the production of a highly glucose-tolerant, extracellular -glucosidase in Aspergillus niger and Aspergillus oryzae. The enzyme was separated from the major and common -glucosidase by gel filtration and that from Aspergillus oryzae further purified by ion-exchange chromatography. It was highly resistant to glucose inhibition (Ki= 953 mM), had a pI of 4.2, optimum pH of 4.5–6.0 and a molecular mass of 30 kDa according to gel filtration. The enzyme was active against cellobiose and alkyl glucosides.