Perylenequinones from Curvularia lunata

Three perylenequinones, the methylated 12-epi-stemphytriol (1), dihydroalterperylenol (2), and alterperylenol (3), were isolated from cultures of Curvularia lunata (LBQM-04) on malt extract broth. All these compounds were obtained from this particular fungus for the first time. Structures of compounds were determined based on MS and NMR spectra, as well as by comparison with the literature reports. The isolation of these phytotoxic reduced perylenequinones from the Curvularia genus suggested that they may occur in any anamorphic fungi belonging to the Pleosporaceae family.     

Curvularia lunata in experimental phaeohyphomycosis

Curvularia lunata strain SP, isolated from a disseminated human infection, infected normal mice, but three other strains of C. lunata and one each of C. pallescens and C. spicifera did not. The SP strain was recovered in cultures from, and hyphal filaments were observed in, abscesses in the liver and spleen of experimentally infected mice. All strains of Curvularia infected mice treated with 400 rads X-irradiation and 10.0 mg cortisone, but at 400 rads and 5.0 mg only two strains of C. lunata (SP and Ghosh) and C. pallescens and C. spicifera infected mice. At 200 rads and 10.0 mg, C. lunata Sp, C. pallescens and C. spicifera; and at 200 rads and 5.0 mg, only C. lunata SP and C. pallescens caused infection. After X-irradiation (200 or 400 rads) or cortisone (5.0 or 10.0 mg) alone only C. lunata SP caused infections in mice.     

Cytotoxic azaphilone alkaloids from Chaetomium globosum TY1

Three novel azaphilone alkaloids, namely chaetomugilides A–C (1–3), together with three related compounds (4–6) were isolated from the methanol extract of Chaetomium globosum TY1, an endophytic fungus isolated from Ginkgo biloba. Their structures were elucidated on the basis of extensive 1D and 2D NMR as well as HRESI-MS spectroscopic data analysis. The isolated compounds exhibited highly cytotoxic activities against human cancer cell line HePG2 with the IC₅₀ values range from 1.7 to 53.4 μM.     

The mitotic configuration of Chaetomium globosum

The somatic nuclear division ofChaetomium globosum was studied utilizing acetocarmin and aceto-orcein techniques. Nuclear division in hyphae of this species was found to be mitotic, but diversity in morphology and division configuration was noted. Identifiable chromosomes, the metaphase plate, and the chromosome bridge were commonly seen.A combination of extremely small nuclei, difficulties in staining, multinucleate conditions, and protoplasmic streaming in hyphae presented difficulties for these studies. Contradictory views are held on the structure of the nucleus, presence of the centriolar body, and other karyological features as described byFinley (1970)Rabinow &Bakerspigel (1965). Nuclear division structural details in a few other fungal species such as the centriolar body, spindle apparatus, and nuclear membrane disassociation have been examined by electron microscopy (Motta, 1969;Ichida &Fuller, 1968;Namboodiri &Lowry, 1967).The present study and the previous report onC. globosum (Hsu, Yu &Volz, 1972) presents comparative data for a NASA Appollo 16 MEED Mycology investigation now in progress.     

A bacteriolytic enzyme from Chaetomium globosum,a marine-isolate

Summary When a marine-isolate, Chaetomium globosum was cultivated in a medium with an increased MgCl₂ content, a bacteriolytic enzyme was extracellularly produced. The enzyme was purified approximately 130-fold. It lyzed Staphylococcus aureus, Micrococcus lysodeikticus and several other Gram-positive bacteria. Optimal pH and temperature for the lysis were 8.0 and 37°C, respectively. The enzyme was heat-labile with maximum stability at neutral pH. Enzymatic activity was greatly stimulated by NaCl and CaCl₂ with maximum activity obtained in the presence of 0.1 M NaCl and 0.003 M to 0.005 M CaCl₂. The activity was stimulated by SH-compounds and was inhibited by SH-reactants.The enzyme is an N-acetylhexosaminidase.     

杜仲内生球毛壳菌的抗氧化活性研究

本文研究了分离自杜仲叶片的内生真菌球毛壳菌菌株No.173发酵液提取物的抗氧化活性,采用铁氰化钾还原力测定法、β-胡萝卜素/亚油酸模型和光照核黄素体系评价了发酵液提取物的抗氧化作用,并采用Folin-Ciocalteu法测定杜仲内生球毛壳菌发酵液提取物总多酚含量。结果表明,其抗氧化能力与Vc基本相当;清除超氧阴离子的能力优于芦丁;多酚含量为255.53±1.38mg/g,是其主要的抗氧化活性成分。     

The meiotic configuration of Chaetomium globosum

Nuclear behavior during ascus development inChaetomium globosum was studied with the use of acetocarmine and aceto-orcein staining techniques. The chromosome behavior, including centriolar bodies and asynchronous disjunction of chromosomes, agreed with the basic pattern reported in Ascomycetes (Olive, 1965). The haploid chromosome complement of this strain appeared to be 6.     

Enzyme profiles and genotyping of Chaetomium globosum isolates from various substrates

The genus Chaetomium is a rich source of novel and bioactive secondary metabolites of great importance. To date, a variety of more than 200 secondary metabolites belonging to diverse structural types have been discovered. Fungal enzymes are used in food, beverages, confectionaries, textiles, and leather industries to simplify the processing of raw materials. They are often more stable than enzymes derived from other sources. Ten isolates of Chaetomium globosum recovered and designated as TUCg1 to TUCg10 were identified by morphological and molecular biology means and submitted to the GenBank. These isolates were screened for extracellular enzymes such as amylase, cellulase, laccase, lipase, pectinases, protease and chitinase on solid media. All Chaetomium globosum isolates screened for potential enzymes showed amylolytic, cellulolytic, and proteolytic activities; six isolates were chitinolytic and laccase producers; and five and three isolates showed pectinolytic and lipolytic activities, respectively. The produced array of enzymes differed among isolates. Molecular techniques such as internal transcribed spacer (ITS) region sequencing and specific genes random primers polymerase chain reaction (SGRP-PCR) have shown high DNA polymorphism of Chaetomium globosum. In conclusion, SGRP-PCR is a rapid and valuable tool for assessment and characterization of genetic diversity of Chaetomium globosum, which suggests the use of this technique for identification of different fungal isolates.     

Chaetoglobosin Vb from endophytic Chaetomium globosum: absolute configuration of chaetoglobosins

One new cytochalasan alkaloid, chaetoglobosin V(b) (1), together with two structurally related known compounds, chaetoglobosin V (2) and chaetoglobosin G (3), was isolated from the ethyl acetate extract of a culture of the endophytic fungus Chaetomium globosum, associated with the leaves of Ginkgo biloba tree. The structures of the isolated compounds were elucidated by spectroscopic methods including 1D and 2D NMR and mass spectrometry. The absolute configuration of chaetoglobosin V(b) (1) was established by means of electronic circular dichroism (CD) spectroscopy, on the basis of the comparison between the CD spectrum of (+)-1 with that calculated with time-dependent density functional theory method for a simplified model. The correlation between compounds 1-3 was demonstrated by a biomimetic transformation of chaetoglobosin G (3) under mild conditions in chaetoglobosins V and V(b) (1 and 2). The isolated metabolites were tested against some phytopathogens.     

Characterization of soluble rifamycin oxidase from Curvularia lunata var. aeria

Curvularia lunata var. aeria was grown on yeast extract, peptone and carboxymethylcellulose (YPC) medium for the production of extracellular rifamycin oxidase. The enzyme was partially purified through a Sephadex G-75 column. The half lives of rifamycin oxidase at 30° and 40°C were 9 d and 100 min, respectively. The activation and deactivation energies of the partially purified enzyme, calculated from Arrhenius plots, were 5.80 and 35.10 kcal mol^-1 respectively. The enzyme exhibited a K _m (rifamycin B) value of 0.67 mmol l^-1 and a V _max of 11 μmol h^-1 ml. Three metal ions, Fe²⁺, Ag⁺ and Hg²⁺, inhibited the enzyme in the 10–20 mmol l^-1 metal ion concentration range. Catalytic activity was not affected by the chelating agent, EDTA.     

Antifungal metabolites from Chaetomium globosum,an endophytic fungus in Ginkgo biloba

From the culture of an endophyte Chaetomium globosum found in Ginkgo biloba, twelve metabolites, including three diketopiperazines, two cytochalasins, two sterols, two simple phenolic compounds, one complex aromatic compound, a nonprotein amino acid and a linear triterpene were isolated. Of them, eight compounds are first reported for the genus Chaetomium. Gliotoxin (8) has good antifungal activity against plant pathogenic fungi.

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Highlights? Twelve compounds were isolated from an endophyte C. globosum harboring inside G. biloba leaves. ? Eight compounds are new for the genus Chaetomium. ? Gliotoxin (8) possessed good antifungal activity against some phytopathogenic fungi.     

The structure and mechanism of action of cellulolytic enzymes

The modern structural classification of polysaccharases comprising cellulase–hemicellulase enzyme systems is dis cussed. Their catalytic domains are currently grouped into 15 of more than 80 known glycosyl hydrolase families, whereas substrate binding domains fall into 13 families. The structures of catalytic and substrate binding domains, as well as linker sequences, are briefly considered. A hypothetical mechanism of concerted action of catalytic and substrate binding domains of cellobiohydrolases on the surface of highly ordered cellulose is suggested.     

Production, Partial Purification and Characterization of Extracelluar Xylanase from Chaetomium globosum

Culture conditions for efficient production of extracellular xylanase by fungus, Chaetomium globosum isolate Cg2, have been standardized. Further, xylanase has been partially purified and characterized. Xylanase activity was maximum after 9 days of incubation when amended in medium with 1.5 % xylan as carbon source and 0.6% NH₄H₂PO₄ as nitrogen source. Partial purification of the xylanase was accomplished by ammonium sulphate precipitation, followed by further purification by anion exchange chromatography on DEAE-Sephadex A-50 column. The partially purified enzyme was electrophoresed on SDS-PAGE and a single band produced corresponded to molecular weight, 32 kD. The optimum temperature and pH for maximum activity of purified xylanase were 30°C and 5.5, respectively. Both the purified xylanase and culture filtrate have shown the antifungal activity against Bipolaris sorokiniana, a causal organism of spot blotch of wheat. Purified xylanase at 100 μg ml^?1 concentration caused 100 per cent inhibition of conidia germination of B. sorokiniana, whereas the culture filtrate was able to inhibit germination up to 67.5 per cent.     

Eumycetoma caused by Curvularia lunata in a dog

Curvularia lunata was cultured from black granules found in granulomatous tumefactions excised from the subcutis of a three year old Medium Schnauzer dog. Draining sinuses were present in some of the tumefactions. Accordingly the diagnosis of eumycotic mycetoma was made. This diagnosis was confirmed by histopathological examination. During the four years following the first surgical intervention, several more similar tumefactions were excised on three different occasions. The dog died of chronic renal failure at the age of 8 years. There was no bone involvement or visceral diffusion of the fungus. The granules were examined by scanning electron microscopy. Immunoglobulins in the dog's serum, assessed by a qualitative test, proved to be equal to immunoglobulins in the serum of a control dog. Precipitating antibodies against C. lunata were not found. The dog was treated for 150 days with itraconazole. In spite of good initial results, recurrence of the fungal lesions were observed after the treatment's interruption. Further treatment with itraconazole for 45 days proved ineffective. No side effects of the drug were observed. This is, to the best of our knowledge, the first case in which C. lunata is identified as the causative agent of an animal eumycetoma.