Modelling the effect of environmental factors on the hyphal growth of the basidiomycete Physisporinus vitreus

The present work investigated the effects of environmental factors on the growth of fungal colonies of the white‐rot basidiomycetes Physisporinus vitreus using a lattice‐free discrete modeling approach called the fungal growth model (FGM), in which hyphae and nutrients are considered as discrete structures. A discrete modeling approach enables the underlying mechanistic rule concerning the basic architecture and dynamics of fungal networks to be studied on the scale of a single colony. By comparing simulations of the FGM with laboratory experiments of fungal colonies growing on malt extract agar we show that the combined effects of water activity, temperature and pH on the radial growth rate of fungal mycelia on the macroscopic scale may be explained by a power law for the costs of hyphal maintenance and expansion on the microscopic scale. Information about the response of the fungal mycelium at the micro‐ scopic level to environmental conditions is essential for simulating its behavior in complex structure substrates such as wood, where the effect of the fungus on the wood (i.e. the degradation of the cell wall) changes the local environmental condition (e.g. the permeability of the substrate and therefore the water activity in a colonized wood cell lumen). Using a combination of diffusion and moisture processes with the FGM may increase our understanding of the colonization strategy of P. vitreus and help to optimize its growth behavior for biotechnological applications such as bioincising. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Weekend compared with weekday presentations of peritoneal dialysis-associated peritonitis

♦ Objective: Management of peritoneal dialysis (PD)-associated peritonitis requires timely intervention by experienced staff, which may not be uniformly available throughout the week. The aim of the present study was to examine the effects of weekend compared with weekday presentation on peritonitis outcomes.♦ Methods: The study, which used data from the Australia and New Zealand Dialysis and Transplant Registry, included all Australian patients receiving PD between 1 October 2003 and 31 December 2008. The independent predictors of weekend presentation and subsequent peritonitis outcomes were assessed by multivariate logistic regression.♦ Results: Peritonitis presentation rates were significantly lower on Saturdays [0.46 episodes per year; 95% confidence interval (CI): 0.42 to 0.49 episodes per year] and on Sundays (0.43 episodes per year; 95% CI: 0.40 to 0.47 episodes per year) than all other weekdays; they peaked on Mondays (0.76 episodes per year; 95% CI: 0.72 to 0.81 episodes per year). Weekend presentation with a first episode of peritonitis was independently associated with lower body mass index and residence less than 100 km away from the nearest PD unit. Patients presenting with peritonitis on the weekend were significantly more likely to be hospitalized [adjusted odds ratio (OR): 2.32; 95% CI: 1.85 to 2.90], although microbial profiles and empiric antimicrobial treatments were comparable between the weekend and weekday groups. Antimicrobial cure rates were also comparable (79% vs 79%, p = 0.9), with the exception of cure rates for culture-negative peritonitis, which were lower on the weekend (80% vs 88%, p = 0.047). Antifungal prophylaxis was less likely to be co-prescribed for first peritonitis episodes presenting on weekdays (OR: 0.68; 95% CI: 0.05 to 0.89).♦ Conclusions: Patients on PD are less likely to present with peritonitis on the weekend. Nevertheless, the microbiology, treatment, and outcomes of weekend and weekday PD peritonitis presentations are remarkably similar. Exceptions include the associations of weekend presentation with a higher hospitalization rate and a lower cure rate in culture-negative infection.     

Activity of Metarhizium spp. and Isaria spp. from the Central Brazilian Cerrado against Triatoma infestans nymphs

Entomopathogenic fungi attack Chagas disease vectors, and there is a need of effective isolates for development of biological control. Ten isolates of Metarhizium spp., four of Isaria cateniannulata and two of an Isaria sp., all isolated with Triatoma infestans as a bait insect from soils collected in Central Brazil, and tested under laboratory conditions were effective against third instar nymphs of T. infestans. This is the first report of pathogenicity of M. flavoviride var. pemphigi, M. robertsii and I. cateniannulata against T. infestans. M. robertsii IP 34 and I. cateniannulata IP 141 are among the most virulent fungi reported, and both have potential for integrated control of triatomine vectors.     

Effects of atrazine, agricultural runoff, and selected effluents on antimicrobial activity of skin peptides in Xenopus laevis

Atrazine (technical and formulation), agricultural runoff containing atrazine, and treated sewage and landfill effluents were evaluated for their potential to modulate antimicrobial activity of Xenopus laevis skin secretions against the chytrid fungus, Batrachochytrium dendrobatidis. This chytrid fungus is implicated in several localized mass mortality events, yet the cause of the susceptibility of amphibians to this newly emergent pathogen is unknown. Antimicrobial peptides secreted from dermal glands are thought to provide critical protection against this pathogen. Chronic exposure of X. laevis larvae to agricultural runoff decreased protein content of collected secretions, while treated wastewater effluents increased protein content. However, the in vitro bioactivity was decreased in treatments with both increased and decreased protein. No differences were observed in protein or bioactivity following laboratory exposures of technical atrazine or a typical atrazine formulation (AAtrex^® 4L/Top Surf^®). These findings demonstrate that exposure of an amphibian model to agricultural runoff or effluent from municipal sewage treatment plants and landfills alters peptide production and in vitro activity of protective peptides. Although evidence suggests peptide production and bioactivity is a critical part of amphibian resistance to pathogens such as the chytrid fungus, the implications of observed effects for immunity and infection are not clear.     

自然杀伤细胞与真菌相互作用的研究新进展

摘要自然杀伤(NK)细胞属于固有免疫效应细胞,无需致敏即可杀伤各种肿瘤细胞及病原体.然而,人们对NK细胞在抗真菌感染方面所起的作用还知之甚少.对NK细胞活化性受体、模式识别受体、下游信号传导及相关细胞因子(IFN-γ、GM-CSF、IL-10等)的研究增加了对NK细胞抗真菌感染免疫机制的认识,并揭示不同的菌体形态也可影...     

血浆1,3-β-D-葡聚糖检测对深部组织真菌感染的诊断价值

目的 探讨血浆1,3-β-D-葡聚糖对早期诊断深部组织真菌感染的临床价值.方法 检测108例深部组织真菌感染患者及20例健康志愿者的血浆1,3-β-D-葡聚糖含量,并对可疑感染标本进行培养.结果 正常对照组血浆1,3-β-D-葡聚糖含量为(5.97±2.94)pg/mL,深部组织真菌感染培养阳性组、深部组织真菌感染培养阴性组血浆1,3-β-D-葡聚糖含量分别为(99.96±37.04 )pg/mL、(31.27±23.67)pg/mL,与正常对照组比较明显升高,存在显著统计学差异(t=18.49、7.70,P<0.05、P<0.05);深部组织真菌感染培养阳性组与深部组织真菌感染培养阴性组比较,存在显著统计学差异(t=11,48,P<0.05).真菌培养法与血浆1,3-β-D-葡聚糖检测法对深部组织真菌感染的诊断阳性率分别为50%及74.07%,血浆1,3-β-D-葡聚糖检测法阳性率明显高于真菌培养法(X2=30.13,P<0.01).结论 血浆1,3-β-D-葡聚糖检测适用于早期诊断假丝酵母菌和曲霉菌引起的临床深部组织感染,可协助临床医生早期诊断用常规方法难以确诊的侵袭性真菌感染.     

一株海绵共附生真菌Fusarium equiseti SCSIO 41019的次级代谢产物及其抑菌活性研究

目的 研究海绵共附生真菌Fusarium equiseti SCSIO 41019的次级代谢产物及抑菌活性。方法 采用中压硅胶柱色谱、中压反相ODS柱色谱及高效液相色谱等方法对发酵产物进行分离和纯化，运用核磁数据及文献对比的方法鉴定化合物结构。采用滤纸片琼脂扩散法、改良肉汤稀释法评价化合物的抑菌活性。结果 从其大米发酵产物中分离并鉴定了8个化合物，分别为equisetin(1)、5'-epiequisetin(2)、lumichrome(3)、N-乙酰基色胺(4)、亚油酸(5)、methyl (4-hydroxyphenyl) acetate(6)、methyl (2-hydroxyphenyl) acetate(7)和graminin B(8)。化合物1、2和5对金黄色葡萄球菌(Staphylococcus aureus)和耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus, MRSA)分别具有不同程度的抑制作用，最小抑菌浓度(minimal inhibitory concentration, MIC)为2.0~125μg/mL，其中化合物1的抑菌活性最强(MIC值分别为2.0和3.9μg/mL)。结论 从菌株Fusarium equiseti SCSIO 41019分离得到两个具良好抑菌活性的化合物(1~2)，为将其开发为耐甲氧西林金黄色葡萄球菌的先导化合物提供一定参考。     

海星共附生真菌Penicillium sp．GGF16－1－2中次级代谢产物研究

目的 全球天然产物社会分子网络（GNPS）和单菌株多次级代谢产物（OSMAC）策略从海洋微生物中寻找结构新颖、活性好的次生代谢产物。方法 在GNPS指导下，通过硅胶柱层析及半制备高效液相色谱（HPLC）等方法对海星共附生真菌penicillium sp. GGF16-1-2在不同培养基的次级代谢产物进行分离纯化。通过核磁共振（NMR）、高分辨质谱（HRMS）、旋光（ORD）和圆二色光谱（CD）等现代波谱解析方法以及对比文献确定化合物的结构。结果 在GNPS追踪指导下从penicillium sp. GGF16-1-2中D培养基分离得到9个聚酮类化合物，依次为phenol A（1）、decarboxydihydrocitrinone（2）、stoloniferol B（3）、sclerotinin A（4）、(1S,3R,4S)-1-(4"-hydroxyl-phenyl)-3,4-dihydro-3,4,5-trimethyl-1H-2- benzopyran-6,8-diol（5）、β-diversonolic ester（6）、sydowinin A（7）、ω-hydroxy-emodin（8）和dibutyl phthalate（9）。而在真1培养基中GNPS预测到二聚体类成分存在，并在GNPS指导下初步分离得到桔霉素二聚类化合物：citrinin H1（10）和dicitrinone B（11）。结论 OSMAC策略和GNPS可以预测并获得骨架丰富、结构新颖的化合物。对海星共附生真菌penicillium sp. GGF16-1-2次生代谢产物研究发现真1培养基比D培养基更适合桔霉素二（多）聚体类化合物的产生。     

Two new xyloketals from the endophytic fungus Endomelanconiopsis endophytica derived from medicinal plant Ficus hirta

Chemical examination of the liquid culture of Endomelanconiopsis endophytica A326 isolated from the Chinese folk medicine Ficus hirta resulted in the isolation of two new xyloketals named xyloketals K and L (1–2) and three known analogs (3–5) including a new natural product (5). Their structures were determined on the basis of extensive spectroscopic analysis. All compounds were evaluated for their cytotoxic activities against the SF-268, MCF-7, NCI-H460, and HepG-2 tumor cell lines. Nonetheless, no significant activity was observed.