Sphingolipid homeostasis in the web of metabolic routes

Sphingolipids play a key role in cells as structural components of membrane lipid bilayers and signaling molecules implicated in important physiological and pathological processes. Their metabolism is tightly regulated. Mechanisms controlling sphingolipid metabolism are far from being completely understood. However, they already reveal the integration of sphingolipids in the whole metabolic network as signaling devices that coordinate different metabolic pathways. A picture of sphingolipids integrated into metabolic networks might help to understand sphingolipid homeostasis. This review describes recent advances in the regulation of de novo sphingolipid synthesis with a focus on the bridges that exist with other metabolic pathways and the importance of this crosstalk in the control of sphingolipid homeostasis. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.     

Transformation of Glycyrrhizic Acid by Aspergillus spp.

Glycryrrhizic acid was metabolized to 3-oxo-18β-glycyrrhetinic acid via 18β-glycyrrhetinic acid by Aspergillus niger, A. oryzae, A. sojae, and A. tamarii. Two methyl esters were derived from these two metabolites and identified by their ¹³C-NMR spectra and MS data.     

致病性曲霉的耐药性研究进展

随着抗真菌药物在临床上的广泛使用,致病性真菌的耐药率越来越高,耐药曲霉对侵袭性曲霉病的诊治产生了重要影响。目前,致病性曲霉耐药性的确定主要依靠抗真菌药敏试验和分子诊断。在有关曲霉耐药机制的研究中,报道最多的是曲霉对唑类药物的耐药,其机制主要包括外排泵表达增加、靶酶Cyp51突变和表达水平增高、形成生物膜,以及热休克蛋白90（Hsp90）介导的信号通路参与而导致的耐药。本文就上述领域近年来的主要进展进行综述。     

曲霉所致鼻面及鼻眶脑真菌病

鼻面及鼻眶脑真菌病（rhinofacial and rhino-orbital-cerebral mycosis,ROCM）是一种病死率高的暴发性真菌感染疾病,主要由毛霉目、虫霉目、蛙粪霉目真菌引起。曲霉属真菌多引起真菌性鼻窦炎,如果侵入邻近的鼻、面、眼眶组织,真菌可能会延伸到颅底和/或神经系统,从而危及生命。由于该类感染早期临床表现缺乏特异性,误诊率可能较高;此外,对曲霉的有效抗真菌治疗与其他真菌的抗真菌治疗有很大的不同。本文对PubMed和中文文献数据库的相关文献进行了系统的Meta分析,全面总结了引起ROCM的相关曲霉菌种类、分布、危险因素、临床表现、诊断和治疗。     

Recent advances in reconstructing microbial secondary metabolites biosynthesis in Aspergillus spp.

High throughput genome sequencing has revealed a multitude of potential secondary metabolites biosynthetic pathways that remain cryptic. Pathway reconstruction coupled with genetic engineering via heterologous expression enables discovery of novel compounds, elucidation of biosynthetic pathways, and optimization of product yields. Apart from Escherichia coli and yeast, fungi, especially Aspergillus spp., are well known and efficient heterologous hosts. This review summarizes recent advances in heterologous expression of microbial secondary metabolite biosynthesis in Aspergillus spp. We also discuss the technological challenges and successes in regard to heterologous host selection and DNA assembly behind the reconstruction of microbial secondary metabolite biosynthesis.     

Disinfection of selected Aspergillus spp. using ultraviolet germicidal irradiation

AIMS: The efficacy of ultraviolet germicidal irradiation (UVGI) and the UVGI dose necessary to inactivate fungal spores on an agar surface for cultures of Aspergillus flavus and Aspergillus fumigatus were determined. METHODS AND RESULTS: A four-chambered UVGI testing unit with a 9-W, Phillips, low pressure, mercury UVGI lamp in each chamber was used in this study. An aperture was adjusted to provide 50, 100, 150, and 200 micro W/cm2 of uniform flux to the surfaces of the Petri dish, resulting in a total UVGI dose to the surface of the Petri dishes ranging from 12 to 96 mJ/cm2. The UVGI dose necessary to inactivate 90% of the A. flavus and A. fumigatus was 35 and 54 mJ/cm2, respectively. CONCLUSIONS: UVGI can be used to inactivate culturable fungal spores. Aspergillus flavus was more susceptible than A. fumigatus to UVGI. SIGNIFICANCE AND IMPACT OF THE STUDY: These results may not be directly correlated to the effect of UVGI on airborne fungal spores, but they indicate that current technology may not be efficacious as a supplement to ventilation unless it can provide higher doses of UVGI to kill spores traveling through the irradiated zone.     

Occurrence of Aflatoxins and Aflatoxin-Producing Strains of Aspergillus spp. in Soybeans

Above average rainfall in Maryland during August, September, and October 1971 resulted in heavy mold growth in soybeans while still in the field. Of 28 samples of soybean seed, aflatoxins were found in 14, 2 of which had been used in poultry feed. Aflatoxins were identified by thin-layer chromatography, spectrophotometry, and chicken embryo bioassay. Aspergillus spp. were isolated from 11 samples, and 5 of these isolates produced aflatoxins when grown in liquid culture.     

Homologous metabolic and gene activating routes for vitamins E and K

Vitamins E and K share structurally related side chains and are degraded to similar final products. For vitamin E the mechanism has been elucidated as initial ω-hydroxylation and subsequent β-oxidation. For vitamin K the same mechanism can be suggested analogously. ω-Hydroxylation of vitamin E is catalyzed by cytochrome P450 enzymes, which often are induced by their substrates themselves via the activation of the nuclear receptor PXR. Vitamin E is able to induce CYP3A-forms and to activate a PXR-driven reporter gene. It is shown here that K-type vitamins are also able to activate PXR. A ranking showed that compounds with an unsaturated side chain were most effective, as are tocotrienols and menaquinone-4 (vitamin K₂), which activated the reporter gene 8–10-fold. Vitamers with a saturated side chain, like tocopherols and phylloquinone were less active (2–5-fold activation). From the fact that CYPs commonly responsible for the elimination of xenobiotics are involved in the metabolism of fat-soluble vitamins and the ability of the vitamins to activate PXR it can be concluded that supranutritional amounts of these vitamins might be considered as foreign.     

Coumarin in Chromosome Analysis

Root tips of monocotyledons were soaked 2.5-3.0 hours at 25-27° C. in saturated aqueous coumarin solution and stained in a mixture of N HC 1 and 2% aceto-orcein (1:9 by volume) 3-4 seconds over a flame. They were then squashed in 1% orcein under a cover glass, the excess stain blotted and the cover sealed. Preparations could be kept about one week. Good chromosome morphology was secured.     

Aspergillus fumigatus tryptophan metabolic route differently affects host immunity

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A Preparation Method of Aspergillus spp. for Scanning Electron Microscopy

For scaning electron microscopy (SEM) of Aspergillus flavus Link und A. petraku Vörös. Simultaneous fixation and drying in osmium tetroxide (O₅O₄ vapours was superior to the conventional preparation methods. Which involve critical point drying. Mycelium exposed to vapours from a solution of 2% O₅O₄ for 24 h at ca. 20°C retained its turger and natural structures. Best results were achived when young mycelium was used. whereas old mycelium always collapased, irrespective of the fixation method used. Use of this method for fixation of Aspergillus spp. is therefore preferable to convennonal methods which are laborious. time-consuming and often interfere with the natural habit of structures. It may also prove usefull with other fungal structures.     

Monitoring Environmental Aspergillus spp. Contamination and Meteorological Factors in a Haematological Unit

The opportunistic pathogens belonging to the Aspergillus genus are present in almost all seasons of the year, and their concentration is related to meteorological conditions. The high density of Aspergillus spp. conidia in a haematological hospital ward may be a significant risk factor for developing invasive fungal diseases in immunocompromised patients. Aim of the present study was to evaluate the variability of airborne Aspergillus spp. conidia contamination in a Haematological Unit (HU) within a period of 16 months in relation with some meteorological parameters. An environmental Aspergillus surveillance was conducted in the HU in four rooms and their bathrooms, in the corridor and in three external sites using an agar impact sampler. During each sampling, temperature and relative humidity at each site were recorded and current wind speed and rainfall events were taken from the official weather service. Aspergillus spp. conidia concentration differed significantly across the sampling sites. Internal Aspergillus spp. loads were significantly dependent on temperature, internal relative humidity and rain. External conidia concentrations were significantly influenced by outdoor temperature and relative humidity. A suitable indicator was introduced to evaluate the seasonal distribution of Aspergillus spp. conidia in the sampling sites, and a significant dependence on this indicator was observed inside the HU. Seventeen different fungal species belonging to the Aspergillus genus were detected during the sampling period. Aspergillus fumigatus was the most frequently isolated species and its distribution depended significantly on the seasonal indicator both inside and outside the hospital ward.