芽孢杆菌酰基高丝氨酸内酯酶基因的克隆及表达

N-酰基高丝氨酸内酯(N—acyl—homoserine hctones．AHLs)作为细菌群体应答系统(Quorum—sensing)中的关键信号分子,其浓度是决定许多动、植物病原菌致病基因的表达的关键因子,酰基高丝氨酸内酯酶基因可以水解AHk丹子的内酯键,使．MILs失去生物活性,从而减弱致病菌的危害．该研究旨在从芽孢杆菌中克隆酰基高丝氨酸内酯酶基因并获得纯化蛋白。根据已知酰基高丝氨酸内酯酶基因的保守序列设计引物,利用PCR方法从2株芽孢杆菌的基因组DNA中克隆出阿个基因SS1和SS10。利用在基因库中进行同源比对．结果表明SS1和SS10编码的蛋白产物SS1和SS10均为酰基高丝氨酸内酯酶。将两个基因在大肠杆菌中诱导表达,通过亲和层析获得了纯化蛋白。     

一株凡纳滨对虾源鳗弧菌群体感应信号分子的检测

旨在检测从凡纳滨对虾体内选取的一株鳗弧菌的群体感应信号分子。利用报告菌株结合薄层层析法鉴定鳗弧菌(Vibrio anguillarum,VA)分泌的高丝氨酸内酯类(AHLs)信号分子,利用哈维氏弧菌V.harveyi JMH597和V.harveyi JAF375作为报告菌株分别检测了VA分泌的AI-2和CAI-1信号分子活性与细菌密度的关系。结果表明,VA能分泌3种类型的信号分子:AHLs信号分子、AI-2信号分子和CAI-1信号分子,其中分泌的AHLs有N-3-羟基-己酰基-高丝氨酸内酯(3-OH-C6-HSL)、N-3-辛酰基-高丝氨酸内酯(C_8-HSL)和N-3-氧代-辛酰基-高丝氨酸内酯(3-oxo-C_8-HSL)。VA分泌的AHLs、AI-2和CAI-1均具有密度依赖性。     

土壤中群体感应淬灭细菌的原位分离与筛选

【背景】许多革兰氏阴性细菌通常以N-酰基高丝氨酸内酯(N-acylhomoserine lactones,AHLs)作为群体感应主要的信号分子。【目的】从土壤中筛选和鉴定新型群体感应淬灭细菌。【方法】通过"垫圈法"从土壤中原位培养分离细菌,采用琼脂条法、报告菌平板法及β-半乳糖苷酶活性测定筛选群体感应淬灭细菌,根据16S rRNA基因序列同源性分析确定菌株系统发育地位。【结果】从不同地区土样中原位培养共分离获得细菌502株。以根癌土壤杆菌Agrobacterium tumefaciens NTL4 (pZLR4)作为报告菌,最终得到11株具有较强降解AHLs能力的细菌,包括假单胞菌5株、不动杆菌4株、变形杆菌和莱茵海默氏菌各1株。大部分细菌可完全降解N-3-羰基十二酰基高丝氨酸内酯(3OC12-HSL),部分细菌对N-(3-氧代己酰)高丝氨酸内酯(3OC6-HSL)和N-3-氧代辛酰高丝氨酸内酯(3OC8-HSL)具有一定降解活性。【结论】Proteus和Rheinheimera可降解AHLs,为今后防治依赖群体感应的植物细菌病害提供新型生防资源。     

食源假单胞菌群体感应信号分子的研究

从市售鲜鱼中分离的3株革兰氏阴性菌,经16S rDNA鉴定为假单胞菌属,该菌是一种导致食品腐败的重要腐败细菌。N-酰基-高丝氨酸内酯(AHLs)是革兰氏阴性菌群体感应(QS)系统中一类重要的信号分子,以密度依赖的方式调控某些生理性状的表达。利用AHLs检测菌株对3株假单胞菌进行检测发现,均产生AHLs类信号分子,且FML05-1和FML05-2至少产生两种AHLs,主要的信号分子是N-3-氧代-辛酰基-高丝氨酸内酯(N- 3-oxo-C_8-HSL)。同时对菌株FML05-2在生长过程中所产生的AHLs的活性变化进行研究,发现AHLs活性在菌体生长至12h时达到最大。首次对食源假单胞菌所产生的AHLs进行了研究,为以干扰腐败细菌群体感应为靶点的食品防腐保鲜策略提供研究基础。     

凡纳滨对虾源不动杆菌群体感应信号分子分离鉴定及其调控

【目的】鉴定凡纳滨对虾源不动杆菌(Acinetobacter spp.M1)分泌的N-酰基高丝氨酸内酯(AHLs)类型,探究细菌生长阶段及环境因素对其分泌信号分子的影响。【方法】报告菌株平板法检测M1的AHLs的活性;采用报告平板与薄层层析(TLC)相结合法对M1分泌的AHLs类型进行鉴定。【结果】菌株M1分泌N-3-氧代-己酰基-高丝氨酸内酯和N-3-氧代-辛酰基-高丝氨酸内酯两种信号分子。在适宜条件下AHLs活性随着培养时间的延长先升高后降低,在对数末期(30 h)达到最大。弱酸和弱碱环境能够降低M1分泌AHLs的能力,p H 7.0是M1分泌AHLs的最适p H。较高浓度的Na Cl促进了个体M1分泌AHLs的能力,但是Na Cl浓度对M1总体分泌AHLs没有显著的影响。菌株M1分泌AHLs的最佳温度为30°C,温度过高或过低都会影响其分泌。【结论】菌株M1主要产生N-3-氧代-己酰基-高丝氨酸内酯和N-3-氧代-辛酰基-高丝氨酸内酯两种类型信号分子。M1的QS系统受菌体密度和环境因素的双重调控。     

植物伴生细菌数量应答系统的研究进展*

N-酰基高丝氨酸内酯(AHLs)作为信号分子介导的细菌数量应答系统参与许多生物学功能的调节,当侵染动植物寄主组织的病原菌繁殖到一定量时,细菌本身产生的AHLs积累到临界浓度,AHLs与胞内特异受体结合,启动致病因子的表达。利用AIRs降解酶和AHLs类似物的特性,干扰和破坏病原菌的AHLs数量应答系统,将为利用现代生物技术防治细菌病害开辟了一条全新的途径。     

不动杆菌属中aidE基因编码高丝氨酸内酯酶

群体感应(Quorum sensing,QS)是细菌在进化过程中形成的依赖于群体密度的细菌间交流方式。许多革兰氏阴性细菌以N-酰基高丝氨酸内酯(AHL)为信号分子,感应自身群体密度并调控致病基因表达。因此,淬灭AHLs信号分子可防治此类细菌引起的植物病害。本实验室前期已筛选得到了一株具有AHLs信号降解能力的不动杆菌菌株Acinetobacter sp.77,本研究通过基因组文库筛选,自菌株77中克隆得到具有AHLs降解活性的基因aidE。该基因编码268个氨基酸。序列一致性比较发现aidE的氨基酸序列与吉伦伯不动杆菌Acinetobacter gyllenbergii CIP110306中β-内酰胺酶一致性高达95%,但与已知的AHLs降解酶序列一致性较低,最高为缓黄分支杆菌Mycobacterium lentiflavum中AHL内酯酶Att M/Aii B家族蛋白(CQD23908.1),一致性仅为33%。通过高压液相色谱(HPLC)分析Aid E蛋白处理N-己酰基高丝氨酸内酯(C6-HSL)的反应产物,证明aidE为AHL内酯酶。序列比对研究发现,aidE基因在不动杆菌属中并不保守,其在菌株77基因组中的上下游的基因排列存在菌株水平的特异性,且aidE基因下游存在疑似IS插入序列,上述证据表明aidE基因有可能是通过水平转移进入Acinetobacter sp.77基因组中,或其在基因组中的位置发生过重排。表达aidE的软腐果胶杆菌Z3-3中完全检测不到AHLs信号产生,且致病力明显降低。综上所述,aidE为新发现的AHL内酯酶。在防治依赖QS系统表达致病性的细菌病害中具有应用潜力。     

细菌群体感应信号分子——酰基高丝氨酸内酯的检测

革兰氏阴性菌根据信号分子N-酰基高丝氨酸内酯(AHLs)的浓度可以监测周围环境中自身或其他细菌的数量变化,当信号分子达到一定浓度阈值时,能启动相关基因的表达来适应环境的变化,这一调控系统被称为细菌的群体感应(quorumsensing,QS)系统。快速简便而有效地检测细菌是否以及产生何种信号分子成为深入研究和了解细菌群体感应的重要手段。现对信号分子AHLs敏感的用于检测不同的信号分子AHLs的微生物传感菌进行综述,并对其检测能力进行了讨论。     

黄河鲤水产细菌的分离及其毒力因子和群体感应信号分子的检测

【背景】水产细菌病害制约水产养殖业健康发展,群体感应与细菌毒力因子的产生密切相关,群体感应调控细菌的毒力因子特性值得进一步研究。【目的】探究群体感应与黄河鲤细菌病害的关系,明确群体感应对细菌毒力因子特性的影响。【方法】通过16S rRNA基因测序并构建系统进化树确定筛选菌株的进化地位,通过脱脂牛奶平板法和偶氮酪蛋白法检测菌株胞外蛋白酶活力,采用结晶紫染色法对菌株的生物膜形成能力进行测定,通过报告菌株BB170和CV026分别测定菌株产信号分子AI-2和高丝氨酸内酯的能力,外源添加高丝氨酸内酯检测信号分子对菌株胞外蛋白酶活力和生物膜形成能力的影响。【结果】哈夫尼亚菌(Hafnia sp.) Z11和气单胞菌(Aeromonas sp.) Z12具有高水平的胞外蛋白酶活力和生物膜形成能力,能够分泌AHLs信号分子且具有菌体密度依赖性。外源添加HSL对菌株毒力因子特性有不同程度的影响,外源添加高浓度的N-丁酰基高丝氨酸内酯(C4-HSL)和N-己酰基高丝氨酸内酯(C6-HSL)能够分别提高菌株Z11和Z12的胞外蛋白酶活力和生物膜形成能力。【结论】高浓度群体感应信号分子AHLs对哈夫尼亚菌和气单胞菌胞外蛋白酶活性有促进作用,说明该2种菌的群体感应现象可能会影响其毒力。     

细菌群体感应LuxR solos蛋白研究进展

N-酰基高丝氨酸内酯(N-acyl-L-homoserine lactones,AHLs)信号分子介导的群体感应(quorum sensing,QS)是一种普遍的革兰氏阴性细菌信息交流方式。AHL-QS系统包括Lux I型AHLs合成酶和LuxR型受体蛋白。然而,部分革兰氏阴性菌缺失1个或多个LuxI型AHLs合成酶,仅有未配对的LuxR型受体蛋白,该LuxR型受体蛋白称为LuxR solo或Orphan蛋白。LuxR solos蛋白在细菌窃听、种间和种内的信号交流中起重要作用,为群体感应研究领域的热点。本文主要综述细菌LuxR solos蛋白的发现、基本概念、蛋白结构及类型,阐述感应AHLs和非AHLs信号分子的重要LuxR solos蛋白及功能,并对群体感应LuxR solos蛋白的研究前景和意义进行了展望。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.