Culture supernatants of patient-derived Aspergillus isolates have toxic and lytic activity towards neurons and glial cells

Infection of the central nervous system by the ubiquitous fungi Aspergillus spp. is a life-threatening disease. Therefore we investigated the mechanism of brain damage by fungal infection. To examine whether secretory factors of Aspergillus isolates derived from patients can induce death of different brain cells, culture supernatants of Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus and Aspergillus niger were added to different astrocytes as well as to the neuroblastoma cell line SK-N-SH, and to the microglial cell line CHME. All four fungal species were shown to secrete toxic factors with neurons being most sensitive against these factors. Very low amounts and short incubation times are sufficient to induce irreversible cell damage, indicating that secreted factors might also affect distant brain regions. Further characterization of the toxic factors revealed that A. fumigatus and A. terreus produced small, heat-stable components whereas the toxic activity of A. niger filtrates was triggered by a high molecular mass factor which could be inactivated by heat. The active component of A. flavus had a molecular mass similar to that of A. niger but was heat-stable and had a significantly lower activity. Taken together these results indicate that secretion of different necrotizing factors might contribute to brain lesions in patients with cerebral aspergillosis.     

Prevalence of otomycosis in malnourished children in Edo State,Nigeria

Out of the total number at 200 suspected cases of otomycoses consisting of 40 malnourished and 160 apparently healthy children examined in this study between the months of July and August in Edo State, 64 Cases (32%) were identified to be of fungal aetiology on the basis of positive culture and careful microscopic exarnination. The state at protein energy malnourishment was deterwined using physicians' comments in their case files. The fungal agents isolated were Aspergillus niger 28 (43.8%); A. fumigatus 4 (25%); Fusarium solari 4 (6.3%); Candida albicans 8 (12.5%); and Hendersonula teruloidea types torn B 5 (6.3%). Of these isolates, A. niger having an solation rate of (43.8%) was found to be the most predominant fungal species associated with otomycosis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Endoglucanase production by paper-degrading mycoflora

Fourteen fungal species, namely Aspergillus flavus, A. fumigatus, A. niger, A. ustus, Penicillium islandicum, P. wortmannii, Memnoniella echinata, Cladosporium herbarum, Stachybotrys atra, Chaetomium globosum, Fusarium oxysporum, Torula herbarum, Alternaria alternata and Curvularia uncinata were isolated from different grades of paper. They differ in their distribution on various kinds of paper and also in relative occurrence. While seasonal influence on mycoflora was observed, most of the moulds were capable of growing in all three seasons examined (summer, winter, rainy season). The moulds were cellulolytic in nature and endoglucanase activity was greatest in Aspergillus flavus, A. niger, A. fumigatus, P. wortmannii and P. islandicum.     

Molecular cloning, nucleotide sequence and expression of the gene encoding prepro-polygalacturonaseII of Aspergillus niger

PolygalacturonaseII of Aspergillus niger was fragmented using CNBr and the NH2-terminal fragment and another fragment were partially sequenced. The polygalacturonaseII (pgaII) gene was then isolated by using an oligonucleotide mixture based on the internal amino acid sequence as a probe. The nucleotide sequence of the pgaII structural gene was determined. It was found that polygalacturonaseII is synthesized as a precursor having an NH2-terminal prepro-sequence of 27 amino acids. The cloned gene was used to construct polygalacturonaseII over-producing A. niger strains. PolygalacturonaseII was isolated from one such strain and was determined to be correctly processed and to be fully active.     

Molecular Identification and Antifungal Susceptibilities of Black Aspergillus Isolates from Otomycosis Cases in Hungary

Otomycosis, also known as fungal otitis externa, has been used to describe a fungal infection of the external auditory canal, but sometimes involving the middle ear. Many fungal species have been identified as infectious agents in otomycosis, with Aspergillus and Candida species being the most common. Among aspergilli, Aspergillus niger is the most commonly described species in the literature. In this study, 14 black Aspergillus strains were analyzed, which were isolated from otomycosis cases in Hungary between 2010 and 2011. These strains were identified as A. niger according to conventional morphological methods. Species identification was based on sequencing of part of the calmodulin gene. Our results indicate that instead of A. niger, A. awamori and A. tubingensis are the predominant species that cause ear infections in Southern Hungary. Antifungal susceptibility tests were carried out against four antifungal drugs: amphotericin B, itraconazole, ketoconazole and terbinafine. All isolates were found to exhibit low in vitro MIC values to amphotericin B, terbinafine and itraconazole. However, the examined isolates exhibited high in vitro MIC values to ketoconazole.     

Posttranslational modification of 6-phosphofructo-1-kinase in Aspergillus niger

Two different enzymes exhibiting 6-phosphofructo-1-kinase (PFK1) activity were isolated from the mycelium of Aspergillus niger: the native enzyme with a molecular mass of 85 kDa, which corresponded to the calculated molecular mass of the deduced amino acid sequence of the A. niger pfkA gene, and a shorter protein of approximately 49 kDa. A fragment of identical size also was obtained in vitro by the proteolytic digestion of the partially purified native PFK1 with proteinase K. When PFK1 activity was measured during the proteolytic degradation of the native protein, it was found to be lost after 1 h of incubation, but it was reestablished after induction of phosphorylation by adding the catalytic subunit of cyclic AMP-dependent protein kinase to the system. By determining kinetic parameters, different ratios of activities measured at ATP concentrations of 0.1 and 1 mM were detected with fragmented PFK1, as with the native enzyme. Fructose-2,6-biphosphate significantly increased the Vmax of the fragmented protein, while it had virtually no effect on the native protein. The native enzyme could be purified only from the early stages of growth on a minimal medium, while the 49-kDa fragment appeared later and was activated at the time of a sudden change in the growth rate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of sequential purifications of PFK1 enzymes by affinity chromatography during the early stages of the fungal development suggested spontaneous posttranslational modification of the native PFK1 in A. niger cells, while from the kinetic parameters determined for both isolated forms it could be concluded that the fragmented enzyme might be more efficient under physiological conditions.     

Physiological characterization of xylose metabolism in Aspergillus niger under oxygen-limited conditions

The physiology of Aspergillus niger was studied under different aeration conditions. Five different aeration rates were investigated in batch cultivations of A. niger grown on xylose. Biomass, intra- and extra-cellular metabolites profiles were determined and ten different enzyme activities in the central carbon metabolism were assessed. The focus was on organic acid production with a special interest in succinate production. The fermentations revealed that oxygen limitation significantly changes the physiology of the micro-organism. Changes in extra cellular metabolite profiles were observed, that is, there was a drastic increase in polyol production (erythritol, xylitol, glycerol, arabitol, and mannitol) and to a lesser extent in the production of reduced acids (malate and succinate). The intracellular metabolite profiles indicated changes in fluxes, since several primary metabolites, like the intermediates of the TCA cycle accumulated during oxygen limitation (on average three fold increase). Also the enzyme activities showed changes between the exponential growth phase and the oxygen limitation phase. In general, the oxygen availability has a significant impact on the physiology of this fungus causing dramatic alterations in the central carbon metabolism that should be taken into account in the design of A. niger as a succinate cell factory.     

Impact of phosphate-solubilizing fungi on the yield and phosphorus-uptake by wheat and faba bean plants

Three fungal isolates (phosphate-dissolvers), Aspergillus niger, A. fumigatus and Penicillium pinophilum were isolated from the rhizosphere of different plants grown in Ismailia and South Sinai Governorates. They effectively solubilized rock phosphate or tricalcium phosphate in Pikovskaya's liquid medium. In pot and column experiments, they significantly reduced pH and increased available phosphorus in the soil treated with either rock phosphate or superphosphate. The yield components of wheat and faba bean plants increased as a result of soil inoculation with the isolated fungi. Penicillium pinophilum was the most efficient isolate. It increased the yield of wheat grains by 28.9 and 32.8% in the soil treated with rock phosphate and superphosphate, respectively. Similarly, it increased the production of faba bean seeds by 14.7 and 29.4% with the same treatments. The uptake of phosphorus by both crops significantly increased due to inoculation of the soil with the tested fungi.     

Advances in citric acid fermentation by Aspergillus niger: biochemical aspects, membrane transport and modeling

Citric acid is regarded as a metabolite of energy metabolism, of which the concentration will rise to appreciable amounts only under conditions of substantive metabolic imbalances. Citric acid fermentation conditions were established during the 1930s and 1940s, when the effects of various medium components were evaluated. The biochemical mechanism by which Aspergillus niger accumulates citric acid has continued to attract interest even though its commercial production by fermentation has been established for decades. Although extensive basic biochemical research has been carried out with A. niger, the understanding of the events relevant for citric acid accumulation is not completely understood. This review is focused on citric acid fermentation by A. niger. Emphasis is given to aspects of fermentation biochemistry, membrane transport in A. niger and modeling of the production process.     

Fungi associated with black tea and tea quality in the Sultanate of Oman

Forty-eight samples of four popular commercial brands of black tea ( Camellia sinensis L.) were purchased from the local markets in Muscat area, Sultanate of Oman. Tea leaves were surveyed for mycoflora. Five fungal species were isolated with A. niger as the most dominant in all the brands having percentage contamination ranging between 0.66% and 30.34%. Other fungi isolated were Aspergillus flavus, Penicillium spp. and Pacelomyces spp. but having average percentages of 0.6%, 0.84% and 0.21% respectively. Significant differences were found among the batches contaminated by A. niger. None of the 25 A. flavus strains screened for aflatoxins were found aflatoxigenic. The total ash, water-soluble ash, and mineral concentration of the samples were within the British standards and were not affected by fungal contamination. The results showed that black tea is contaminated by fungi that might constitute health hazards for humans. The post harvest contamination of tea could be eliminated or reduced if processing is conducted under more hygienic conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

白腐菌对木质素降解能力的测定

本文测定了7种霉菌对木质素的降解作用。结果表明,在测试的7种霉菌中,米曲霉(Aspergillus oryzal)2013、米曲霉2014、米曲霉2015和黑曲霉(Aspergillus niger)对木质素的降解能力较强,其降解率均达到90%以上。野外分离得到的细菌对木质素没有降解作用。     

Citric acid production by Aspergillus niger on wet corn distillers grains

AIMS: To determine which citric acid-producing strain of Aspergillus niger utilized wet corn distillers grains most effectively to produce citric acid. METHODS AND RESULTS: Citric acid and biomass production by the fungal strains were analysed on the untreated grains or autoclaved grains using an enzyme assay and a gravimetric method respectively. Fungal citric acid production on the grains was found to occur on the untreated or autoclaved grains. The highest citric acid level on the grains was produced by A. niger ATCC 9142. The autoclaved grains supported less citric acid production by the majority of strains screened. Biomass production by the fungal strains on the untreated or autoclaved grains was quite similar. The highest citric acid yields for A. niger ATCC 9142, ATCC 10577, ATCC 11414, ATCC 12846 and ATCC 26550 were found on the untreated grains. Treatment of the grains had little effect on citric acid yields based on reducing sugars consumed by A. niger ATCC 9029 and ATCC 201122. CONCLUSIONS: It is feasible for citric acid-producing strains of A. niger to excrete citric acid on wet corn distillers grains whether the grains are treated or untreated. The most effective citric acid-producing strain of A. niger was ATCC 9142. SIGNIFICANCE AND IMPACT OF THE STUDY: The study shows that the ethanol processing co-product wet corn distillers grains could be utilized as a substrate for the commercial production of citric acid by A. niger without treatment of the grains.     

Isolation and evaluation of tannin-degrading fungal strains from the Mexican desert

Eleven fungal strains (4 Penicillium commune, 2 Aspergillus niger, 2 Aspergillus rugulosa, Aspergillus terricola, Aspergillus ornatus and Aspergillus fumigatus) were isolated, characterized morphologically and by their capacity to degrade tannins. Aspergillus niger Aa-20 was used as control strain. Several concentrations of hydrolysable tannin (tannic acid) were used as sole carbon source. All strains were able to degrade hydrolysable tannins. Aspergillus niger GH1 and PSH showed the highest tannin-degrading capacity (67 and 70%, respectively). Also, the fungal capacity to degrade condensed tannin (catechin) was tested. Aspergillus niger PSH and Penicillium commune EH2 degraded 79.33% and 76.35% of catechin. The results demonstrated the capacity of fungi to use hydrolysable and condensed tannins as carbon source.     

Inhibition of ABCG2-mediated drug efflux by naphthopyrones from marine crinoids

Five new naphthopyrones (1–5) along with the known compounds TMC-256A1, 5,8-dihydroxy-6-methoxy-2-propyl-4H-naphtho[2,3-b]pyran-4-one, TMC-256C1, comaparvin, 6-methoxycomaparvin, and 6-methoxycomaparvin 5-methyl ether (6–11) were isolated from crinoids of the family Comasteridae. All compounds were tested for their ability to inhibit the multidrug transporter ABCG2, which plays a role in drug resistance. Six of the seven angular naphthopyrones showed moderate activity with <60% inhibition of ABCG2-mediated transport as compared to the positive control fumitremorgin C. None of the linear naphthopyrones inhibited ABCG2-mediated efflux.     

Seed-borne fungi of five cruciferous vegetables and relative efficacy of aqueous seed extracts against some associated fungi

A total of 121 seed samples of cabbage, cauliflower, cress, radish and turnip collected from five localities in Upper Egypt were assayed for their fungal flora. The highest count of fungi was recorded on cabbage seeds (75%), whereas the lowest count was observed on turnip seeds (33%). Thirty-five fungal species and two varieties belonging to 16 genera were identified. The broadest number of species (22 species + 1 variety) were isolated from cress seeds. However, only five species,viz. Aspergillus flavus, A. niger, Penicillium chrysogenum, P. funiculosum andRhizopus stolonifer, were found to be associated with seeds of the five plants. The relative efficacy of aqueous seed extracts against these five fungal species was tested. The antifungal drug Trosyd (tioconazole) was taken as a standard inhibitor. The aqueous extract of cabbage seeds inhibited three fungal species, cress extract two and cauliflower and turnip one species; radish seed extract was ineffective.     

法夏内生菌株D126产细胞毒活性物质布雷菲德菌素A的研究(英文)

药用植物法夏内生真菌D126,当进行液体培养时能产细胞毒活性物质,经核磁共振氢谱、碳谱和快原子轰击质谱确定,该物质为布雷菲德菌素A(BFA).进一步研究表明,BFA对人Burkitt's 淋巴瘤细胞株Raji、人肝癌细胞株HepG2和人非小细胞肺腺癌细胞株A549具有较强的抑制活性,对植物病原真菌黑曲霉和杨桃炭疽菌等具有抑菌活性.最后,对植物内生真菌产细胞毒活性物质BFA的生态意义进行了探讨.     

Isolation of sterols from the marine fungus Corollospora lacera

Several marine fungi collected from the waters of Prince Edward Island, Canada, were screened for the presence of natural products exhibiting antibacterial activity. Both broths and mycelia of these fungi were studied using the bioassay-guided chromatographic separation. The 4 fractions from the extract of mycelia of Corollospora lacera exhibited weak antibacterial activity and were analyzed further. From these fractions, 2 sterols (5 alpha,8 alpha-epidioxyergosterol and 22E,24R-ergosta-7,22-diene-3beta,5 alpha,6 beta-triol) and a 3:1 mixture of linoleic and oleic acids were isolated. The presence of ergosterol was confirmed in dichloromethane extracts of mycelia of every fungus in this study and this sterol was isolated from the extract of mycelium of Corollospora lacera. Two other known compounds (5-hydroxymethylfuran-2-carbaldehyde and bis(2-ethylhexyl) phthalate), were isolated from the dichloromethane extract of mycelium of Monodictys pelagica. The phthalate was reported in the literature as a metabolite isolated from the fungi, but in our study it was proven to be an artifact of the culturing and (or) extraction procedures rather than a true fungal metabolite.