Pyrostatins A and B,New Inhibitors of N-Acetyl-β-D-Glucosaminidase,Produced by Streptomyces sp. SA-3501

Abstract

Pyrostatins A and B, new inhibitors of N-acetyl-β-D-glucosaminidase(G1cNAc-ase), have been purified from the culture broth of Streptomyces sp. SA-3501 isolated from a marine environment. They were purified by chromatography on Dowex 50W, silica gel and Capcell Pak C₁₈(HPLC) followed treatment with active carbon and then isolated as white powders. The structures of pyrostatins A and B were determined by NMR studies to be 4-hydroxy-2-imino-l-methylpyrrolidine-5-carboxylic acid and 2-imino-l-methylpyrrolidine-5-carboxylic acid, respectively. They were competitive with the substrate, and the inhibition constants(K_i) of pyrostatins A and B were 1.7 × 10^-6 M and 2.0 × 10^-6 M respectively.     

Microbial effects on plant phenology and fitness

Plant development and the timing of developmental events (phenology) are tightly coupled with plant fitness. A variety of internal and external factors determine the timing and fitness consequences of these life-history transitions. Microbes interact with plants throughout their life history and impact host phenology. This review summarizes current mechanistic and theoretical knowledge surrounding microbe-driven changes in plant phenology. Overall, there are examples of microbes impacting every phenological transition. While most studies have focused on flowering time, microbial effects remain important for host survival and fitness across all phenological phases. Microbe-mediated changes in nutrient acquisition and phytohormone signaling can release plants from stressful conditions and alter plant stress responses inducing shifts in developmental events. The frequency and direction of phenological effects appear to be partly determined by the lifestyle and the underlying nature of a plant–microbe interaction (i.e., mutualistic or pathogenic), in addition to the taxonomic group of the microbe (fungi vs. bacteria). Finally, we highlight biases, gaps in knowledge, and future directions. This biotic source of plasticity for plant adaptation will serve an important role in sustaining plant biodiversity and managing agriculture under the pressures of climate change.     

妇科疾病患者PICC置管后感染者病原菌分布及T淋巴细胞亚群变化

目的研究妇科疾病患者外周静脉植进中心静脉导管(PICC)后感染者病原菌分布及T淋巴细胞亚群水平变化。方法选取2017年3月至2019年5月在我院接受PICC置管治疗的63例妇科疾病患者为观察组,另外选取同期我院健康体检女性50例为对照组,采用菌种分离鉴定法分析观察组患者病原菌分布,并比较观察组和对照组对象T淋巴细胞亚群和白细胞介素6(IL-6)、肿瘤坏死因子α(TNF-α)水平。结果共分离出102株细菌,其中以大肠埃希菌(19.61%)、肺炎克雷伯菌(14.71%)、铜绿假单胞菌(9.80%)为主的革兰阴性菌占比最高(50.98%);其次是革兰阳性菌,占34.31%;真菌数量最少,占14.71%。感染前后观察组患者CD3~+细胞、CD4~+细胞及CD4~+/CD8~+水平显著低于对照组(均P0.05),而CD8~+细胞及IL-6、TNF-α水平显著高于对照组对象(均P0.05)。感染后,观察组患者CD3~+细胞、CD4~+细胞及CD4~+/CD8~+水平显著低于感染前,CD8~+细胞及IL-6、TNF-α水平显著高于感染前(均P0.05)。结论妇科疾病患者PICC置管后感染者病原菌以大肠埃希菌、肺炎克雷伯菌、铜绿假单胞菌等革兰阴性菌为主,感染后患者T淋巴细胞亚群及炎性因子水平严重失调,患者免疫功能减弱。     

人工栽培蛹虫草的病原真菌

蛹虫草规模化栽培过程中,真菌病害普遍发生且危害严重。本研究对人工栽培蛹虫草中真菌病害进行调研,对病原真菌进行分离、纯化、鉴定及致病性检验,并分析病害发生的特点。结果发现引起蛹虫草病害的病原真菌主要有虫草生齿梗孢、产扁虫菌素单端孢、镰刀菌、裂褶菌、哈茨木霉、淡紫拟青霉、稻绿核菌、粉红枝穗霉、卵孢单端孢、扩展青霉、黄曲霉和黑曲霉。其中虫草生齿梗孢为引起蛹虫草侵染性病害的主要病原真菌。虫草生齿梗孢、产扁虫菌素单端孢、镰刀菌、裂褶菌和哈茨木霉主要为害蛹虫草子实体;淡紫拟青霉、稻绿核菌、粉红枝穗霉、卵孢单端孢、扩展青霉、黄曲霉和黑曲霉主要为害栽培料与蛹虫草菌丝体。镰刀菌、裂褶菌、哈茨木霉、淡紫拟青霉、稻绿核菌和粉红枝穗霉为引起蛹虫草病害的首次报道。本研究为蛹虫草病害防控奠定基础,以促进产业健康发展。     

数字PCR在食源性致病菌检测中的应用进展

食源性致病菌是食品安全的重大隐患,对人类健康造成极大危害,因此亟待研究和建立精准有效的食源性致病菌检测方法。随着单分子检测技术的快速发展,数字PCR技术因其具有超高的灵敏度、稳定性和低试剂消耗等优点而被广泛应用于食源性致病菌的检测。主要介绍了数字PCR的基本原理及其研究进展,深入探讨了其在检测大肠杆菌（Escherichia coli）、沙门氏菌（Salmonella）、金黄色葡萄球菌（Staphylococcus aureus）、空肠弯曲菌（Campylobacter jejuni）、志贺氏菌（Shigella）、克罗诺杆菌（Cronobacter）、副溶血性弧菌（Vibrio parahaemolyticus）、单核细胞增生李斯特氏菌（Listeria monocytogenes）和蜡状芽孢杆菌（Bacillus cereus）中的应用,为今后该技术在食源性致病菌检测中的研究与应用提供一定的技术性参考。     

基于同源基因的病原菌鉴定和分型靶位点的功能基因组学研究

利用病原菌序列差异,对病原菌特定基因和位点进行检测,可以快速发现和鉴别病原菌的分类和特征,对传染病快速诊断和溯源具有基础性意义和重要价值.本文旨在覆盖中国重要传染病的103种病原菌,寻找各分类阶元中特有的同源基因,并从中挑选出适合用于病原菌鉴定、分型的候选基因.利用生物信息学和基因组学方法,对已有全基因组序列的275株病原菌的836415个基因进行比对分析,进一步明确菌株的门、纲、目、科、属各分类阶元中特有的同源基因集合;通过COG功能分类方法,对同源基因集合进行功能注释,并分析在不同分类阶元内的保守基因功能的变化规律.本研究寻找到适合鉴定和分型的不同分类阶元（门、纲、目、科、属）的同源基因集合共19563个（门2891个、纲1016个、目3601个、科10130个、属1925个）.对同源基因功能的分析表明,适合对病原菌进行鉴定的基因在不同分类阶元中,表现的功能存在较大差异.革兰氏阳性和阴性病原菌在不同分类阶元中,同源基因表现出的功能也存在差异.该结果将为对在中国广泛存在的病原菌进行检测所涉及的探针、芯片设计提供理论依据,加快目标探针的筛选工作.同时,研究也是首次将世界范围内的全基因组数据和中国重大传染病涉及的病原菌紧密联系结合,为利用功能基因组学开展区域性、有针对性的病原检测和监测,提供候选基因和位点筛选的新方法.相关结果在细菌的元基因组学研究中也具有一定的应用价值.     

An isothermal absorptiometric assay for viable microbes using the redox color indicator 2,6-dichlorophenolindophenol

A simple and rapid isothermal absorptiometric assay for detection of viable microbes using the redox color indicator 2,6-dichlorophenolindophenol (DCPIP) was studied. The absorbance of DCPIP decreased at 600 nm because of a redox reaction occurring between DCPIP and the surface membrane of viable microbes and was inversely proportional to the viable cell density. The redox reaction was found not only with bacteria, but also with yeast and a mixture of bacteria and yeast. In this assay, the influence of light scattering and absorption caused by microbial cells and coexisting substances in the sample was excluded by a time difference method. The assay required only 10 min for one incubation mixture, and highly repeatable results from three consecutive measurements were obtained by isothermal incubation for specific times at 30 °C using a thermostable three-cuvette-stir system. Thus, the cell density of microbial cell suspensions or growth medium was successfully determined, and a practical lower detection limit for food inspection was obtained at 10⁴–10⁶ cfu/ml. Single-cell effects on DCPIP reduction were evaluated and compared between species. Consequently, this assay is expected to be a useful tool for the rapid measurement of viable microbes as a preliminary assay for the Hazard Analysis Critical Control Point program.     

Pathogenic variability of Pseudoperonospora cubensis in Gangetic Alluvial region of West Bengal,India

Cucurbits are tremendous economically important vegetable crops and extensively cultivated in tropical and subtropical part of the world during both rainy and winter seasons. Biotic stresses are of paramount importance in causing economic losses in cucurbits. Downy mildew, a foliar disease caused by an Oomycetes, Pseudoperonospora cubensis (Berk. & Curt.) Rostow, is one of the most destructive pathogens of cucurbits especially in wet and temperate regions, with worldwide distribution. Isolates of pointed gourd and ivy gourd showed no symptoms with most of the cucurbits hosts except pointed gourd and ivy gourd. P. cubensis isolate of pointed gourd differed from other isolates and may belong to different pathotype. The results of this investigation suggest that high variability of P. cubensis in terms of different pathotypes exists in the Gangetic Alluvial Region of West Bengal. Based on morphological characterisation, nine isolates of P. cubensis are grouped into four clusters by using hierarchical cluster analysis.     

In vitro kinetics and antifungal activity of various extracts of Terminalia chebula seeds against plant pathogenic fungi

The aim of the present study was to examine the efficacy of various seed extracts of Terminalia chebula as an antifungal potential against certain important plant pathogenic fungi. The organic extracts of methanol, ethyl acetate and chloroform at the used concentration of 1500 ppm/disc revealed remarkable antifungal effect as a fungal mycelial growth inhibitor against Fusarium oxysporum, Fusarium solani, Phytophthora capsici and Botrytis cinerea, in the range of 41.6–61.3%, along with MIC values ranging from 62.5 to 500 μg/ml. Also, the extracts had a strong detrimental effect on spore germination of all the tested plant pathogens along with concentration as well as time-dependent kinetic inhibition of B. cinerea. The results obtained from this study suggest that the natural products derived from Terminalia chebula could become an alternative to synthetic fungicides for controlling such important plant pathogenic fungi.