浅析环境特征对遗传多样性与物种多样性的平行效应

遗传多样性与物种多样性是生物多样性的两个基本层次。近年来的研究表明,环境特征可能对种群遗传多样性与群落物种多样性产生平行效应。本文对遗传多样性与物种多样性关联模型中环境特征对遗传多样性与物种多样性的平行效应部分进行了具体化介绍。基于群落形成的四个基本过程,即突变与物种形成、选择、漂变和扩散,探讨了环境特征对遗传多样性与物种多样性产生平行效应的理论基础。在全球变化的大背景下,研究环境特征对遗传多样性与物种多样性的平行效应及这两个维度多样性对全球变化响应的异同具有重要的生态学与保护生物学意义。然而,目前大多数生物多样性研究仍然只基于物种多样性一个维度,在同一系统中同时对遗传多样性与物种多样性进行整合研究的工作仍然较少。希望通过本文的总结与讨论,能对国内遗传多样性与物种多样性整合研究起到参考与促进作用。     

植物边缘种群遗传多样性研究进展

边缘种群指地理分布边缘可检测到的一定数量的同种个体集合, 准确评价其遗传多样性对于理解第四纪冰期后气候变化对物种边缘扩展或收缩、遗传资源保护与利用以及物种形成等有重要意义。该文探讨了维持植物边缘种群遗传多样性的进化机制, 分析交配系统对物种边缘及其遗传多样性的影响, 比较了边缘与中心种群遗传多样性的差异及其形成的生态与进化过程, 并探讨了边缘种群遗传多样性与其所在的群落物种多样性的关系及理论基础。该文提出今后研究的重点是应用全基因组序列或转录组基因序列研究前缘-后缘种群之间或边缘-中心种群之间的适应性差异, 边缘种群与所在群落其他物种之间相互作用的分子机制, 深入解析边缘种群对环境的适应及边缘种群遗传多样性与群落物种多样性关系的生态与进化过程。     

农业土壤微生物基因与群落多样性研究进展

介绍了群落基因组多样性、结构多样性与功能多样性相互关系的研究方法 ,重点论述了近年来农业土壤微生物群落遗传、结构与功能多样性的研究进展。同时总结了耕作措施和养分管理对农业土壤微生物群落多样性的影响 ,提出微生物序列分析、比较基因组学和微生物芯片技术与传统研究技术结合将有助于对微生物群落结构与功能和生物与环境因素对土壤微生物群落影响的深刻理解     

微生物的生物多样性及应用前景*

根据微生物的特性,从物种、生理代谢类群及遗传背景几个方面简述了它们的生物多样性及其研究的重要意义。并从基因组学的研究发展展望了对微生物多样性的认识和其资源利用的前景,希望能引起科学界和全社会对这个生物资源的重视。     

环境污染对生物多样性的影响

环境污染并不是一种一般意义上的环境胁迫 ,生物对污染的适应机制及进化格局与自然胁迫条件下的情形并不相同。环境污染是一种生态破坏 !随着研究工作的不断深入和系统化 ,人们越来越发现 ,环境染污引起物种丧失实质上也是一种生态破坏 ,而且认为当今世界正在经历的物种大灭绝在很大程度上与全球扩散的环境污染有密切联系。以下分别在遗传、物种和生态系统水平上讨论污染对生物多样性的影响。1　遗传多样性的丧失遗传多样性强调的是现有种质的遗传变异库存量 ,它既是生物遗传变异的历史积累 ,反映了生物的进化过程 ,也是现有生物适应现有环…     

微生物降解硝基芳烃及其卤代衍生物的研究进展

硝基芳烃化合物作为一种重要的化工原料,广泛应用于医药、染料、农药等化工产品的合成。在给人类社会带来空前的物质繁荣的同时,其造成的环境污染问题也成为人类社会面临的重要挑战之一。微生物在这些环境污染物的降解中起着重要的作用。近几十年,环境微生物工作者对微生物降解硝基芳香污染物的各个步骤,包括趋化感应、分解代谢及生物修复进行了大量的研究工作,获得了丰富的知识。本文综述了硝基芳烃及其卤代衍生物的微生物代谢途径、代谢机理、趋化及修复研究进展,并对本领域的研究进行了展望,有助于全面认知硝基芳烃污染物的微生物降解过程,为污染环境修复提供理论基础。     

原核微生物的多样性

微生物是一群以分解代谢为主的重要生物类群,其生物学多样性十分丰富。但由于它们的微观性,尤其原核微生物简单的单细胞结构、以无性方式进行快速地繁殖而造成的无准确的基线难以对其进行种群数目和数量的统计,因而对微生物的多样性研究远没有宏观生物那样深入和受到重视。本文根据原核微生物的特性,从其物种、所代表的进化分支、生理代谢类群及遗传背景几个方面简述了它们的多样性及重要意义,意在引起科学界和全社会对这类生物资源的认识和保护的重视。     

微生物群落多样性数学表征方法及其在污水处理系统研究中的应用

微生物群落在调节全球气候、人类健康和工业生物技术应用中扮演着重要角色。定量表征微生物群落多样性是认识微生物群落基本特征、动态变化和功能的前提。本文介绍了常用的α多样性指数,包括物种数目、Shannon-Weaver指数、Simpson多样性指数和Hill多样性指数;并介绍了其他多样性评估方法及其原理,包括能够评价样本对微生物群落各物种覆盖程度的稀释性曲线和Good’s coverage指数,以及能估算群落多样性的Chao1、ACE指数和基于物种丰度分布曲线的模型方法;并以最大规模的生物技术应用——污水处理厂为例,介绍了这些方法在认识微生物群落多样性中的应用。现有研究表明:所检测到的城市污水处理厂中微生物群落的物种数目和Shannon-Weaver指数随检测方法解析通量(样本大小)的增加而增大;但现有方法仍无法反映城市污水处理厂微生物群落的真实多样性。基于特定的物种丰度分布曲线对DNA样本数据进行模拟和重建,结果表明对群落物种数目的评估存在较大的不确定性;Shannon-Weaver指数,特别是Simpson多样性指数等受低丰度物种影响较小,可以准确计算,是评价和比较微生物群落分类学多样性的好手段。改进模型拟合方法和加大取样深度能提高微生物群落物种数目的评估精度。此外,认识微生物群落其他方面的多样性如系统发育多样性和功能多样性,也对认识微生物生态特征具有重要意义。     

豫西山区日本落叶松林下植物物种多样性的研究

生物多样性是指各种生命形式的资源,它包括地球上所有植物、动物、微生物物种及它们所有基因,以及生物与其环境相互作用形式的生态系统与生物过程,它包括三个层次,即遗传多样性、物种多样性与生态系统多样性［１］。生物多样性对人类生存与发展,以及对维持整个地球的...     

微生物菌剂在难降解有机污染治理的研究进展

大量的难降解有机污染物被排放到环境中,因其蓄积性、持久性和生物毒性,对人类健康和生态环境造成严重危害。近年来,利用微生物菌剂治理难降解有机污染物的研究已取得较好的进展。综述微生物菌剂在国内外的发展历程,介绍微生物菌剂制备中常用的固定化技术及载体材料,并分析总结微生物菌剂在酚类物质、多环芳烃和多氯联苯等有机污染物治理中的研究进展。在此基础上,提出治理难降解有机污染物的微生物菌剂研发所存在的主要问题及其展望。     

Metabolic regulation of fermentation processes

To compete in nature against other forms of life, microorganisms possess regulatory mechanisms which control production of their metabolites, thus, protecting against overproduction and excretion of these primary and secondary metabolites into the environment. To effect such an economical form of life, they possess regulatory mechanisms which control production of these metabolites and protect against overproduction and excretion into the environment of excess concentrations. In the field of industrial fermentation, the opposite concept prevails. Fermentation microbiologists search for a rare overproducing strain in nature, then further deregulate the microorganism so that it overproduces huge quantities of a desired commercially important product such as a metabolite or an enzyme. Deregulation is brought about by nutritional as well as classical and molecular genetic manipulations to bypass and/or remove negative regulatory mechanisms and to enhance positive regulatory mechanisms. These mechanisms include induction, nutritional regulation by sources of carbon, nitrogen and phosphorus, and feedback control. The controls and their modification by biotechnologists are the subjects of this review.     

Genetic background and environmental conditions drive metabolic variation in wild type and transgenic soybean (Glycine max) seeds

The metabolic profiles and composition of storage reserves of agricultural crop seeds are strongly regulated by heritable and environmental factors. Yet, very little is known about the genetic and environmental determinants of adaptive metabolic variation amongst wild type as well as transgenic seed populations derived from the same genetic background, grown under natural field conditions. The goal of the current study was to investigate the effects of natural environmental conditions on wild type and transgenic soybean seeds expressing a feedback‐insensitive form of cystathionine γ‐synthase, a methionine main regulatory enzyme. The seeds were grown in four geographically distinct habitats in China and then assayed for primary metabolic profiles using gas chromatography mass spectrometry, morphological traits and storage reserve accumulation. The analyses revealed changes in the levels of primary metabolites which evidently exhibited high correlation to methionine regardless of changes in environmental conditions. The environment, however, constituted a major determinant of metabolic profiles amongst seeds, as much more metabolites were observed to be affected by this variable, particularly along the north‐to‐south latitudinal gradient. The observations suggest that metabolic variation amongst seeds grown under natural field conditions depends upon the complex relationships existing amongst their genetic background and the environmental conditions characterizing their cultivation areas.     

Background levels of polycyclic aromatic hydrocarbons (PAH) and selected metals in new England urban soils

Polycyclic aromatic hydrocarbons (PAH) are byproducts of combustion and are ubiquitous in the urban environment They are also present in industrial chemical wastes, such as coal tar, petroleum refinery sludges, waste oils and fuels, and wood‐treating residues. Thus, PAHs are chemicals of concern at many waste sites. Risk assessment methods will yield risk‐based cleanup levels for PAHs that range from 0.1 to 0.7 mg/kg. Given their universal presence in the urban environment, it is important to compare risk‐based cleanup levels with typical urban background levels before utilizing unrealistically low cleanup targets. However, little data exist on PAH levels in urban, nonindustrial soils. In this study, 60 samples of surficial soils from urban locations in three New England cities were analyzed for PAH compounds. In addition, all samples were analyzed for total petroleum hydrocarbons (TPH) and seven metals. The upper 95% confidence interval on the mean was 3 mg/kg for benzo(a)pyrene toxic equivalents, 12 mg/kg for total potentially carcinogenic PAH, and 25 mg/kg for total PAH. The upper 95% confidence interval was 373 mg/kg for TPH, which exceeds the target level of 100 mg/kg used by many state regulatory agencies. Metal concentrations were similar to published background levels for all metals except lead. The upper 95% confidence interval for lead was 737 mg/kg in Boston, 463 mg/kg in Providence, and 378 mg/kg in Springfield.     

Engineering of a psychrophilic bacterium for the bioremediation of aromatic compounds

Microbial degradation of aromatic hydrocarbons has been studied with the aim of developing applications for the removal of toxic compounds. Efforts have been directed toward the genetic manipulation of mesophilic bacteria to improve their ability to degrade pollutants, even though many pollution problems occur in sea waters and in effluents of industrial processes which are characterized by low temperatures. From these considerations the idea of engineering a psychrophilic microorganism for the oxidation of aromatic compounds was developed.In a previous paper it was demonstrated that the recombinant Antarctic Pseudoalteromonas haloplanktis TAC125 (PhTAC/tou) expressing a toluene-o-xylene monooxygenase (ToMO) is able to convert several aromatic compounds into corresponding catechols. In our work we improved the metabolic capability of PhTAC/tou cells by combining action of recombinant ToMO enzyme with that of the endogenous P. haloplanktis TAC125 laccase-like protein. This strategy allowed conferring new and specific degradative capabilities to a bacterium isolated from an unpolluted environment; indeed engineered PhTAC/tou cells are able to grow on aromatic compounds as sole carbon and energy sources. Our approach demonstrates the possibility to use the engineered psychrophilic bacterium for the bioremediation of chemically contaminated marine environments and/or cold effluents.     

微生物降解石油烃的功能基因研究进展

微生物对石油烃的降解在自然衰减去除土壤和地下水石油烃污染的过程中发挥了重要作用。微生物通过其产生的一系列酶来利用和降解这类有机污染物,其中,编码关键降解酶的基因称为功能基因。功能基因可作为生物标志物用于分析环境中石油烃降解基因的多样性。因此,研究石油降解功能基因是分析土著微生物群落多样性、评价自然衰减潜力与构建基因工程菌的重要基础。本文主要介绍了烷烃和芳香烃在有氧和无氧条件下的微生物降解途径,重点总结了烷烃和芳香烃降解的主要功能基因及其作用,包括参与羟化作用的单加氧酶和双加氧酶基因、延胡索酸加成反应的琥珀酸合酶基因以及中心中间产物的降解酶基因等。     

Regulation of the -arabinose operon of Escherichia coli

Over forty years of research on the -arabinose operon of Escherichia coli have provided insights into the mechanism of positive regulation of gene activity. This research also discovered DNA looping and the mechanism by which the regulatory protein changes its DNA-binding properties in response to the presence of arabinose. As is frequently seen in focused research on biological subjects, the initial studies were primarily genetic. Subsequently, the genetic approaches were augmented by physiological and then biochemical studies. Now biophysical studies are being conducted at the atomic level, but genetics still has a crucial role in the study of this system.     

A quantitative genetics and ecological model system: understanding the aliphatic glucosinolate biosynthetic network via QTLs

Plants’ sessile nature has led them to develop chemical defenses, secondary metabolites, to directly cope with environmental changes rather than escape to more favorable sites. The diversity and fluctuation in biological stresses faced by a plant have generated extraordinary genetic diversity controlling the synthesis and regulation of secondary metabolites that is only now being explored. The glucosinolate secondary metabolites, amino acid derived thioglucosides specific to the order Capparales, is a model system for understanding the molecular basis of complex quantitative traits and their potential ecological role. This review focuses on the extensive progress being made towards understanding the complete molecular basis underlying the glucosinolate genetic diversity at both biosynthetic and regulatory loci. This has identified a highly interactive genetic network whereby biosynthetic loci have additional functions as regulatory loci and laid the foundation for glucosinolates to be a model system for understanding quantitative traits in a broader context.     

Prospects for utilising plant-adaptive mechanisms to improve wheat and other crops in drought- and salinity-prone environments

Breeding for adaptation to abiotic stress is extremely challenging due to the complexity of the target environments as well as that of the stress‐adaptive mechanisms adopted by plants. While many traits have been reported in the literature, these must be considered with respect to the type of environment for which a cultivar is targeted. In theory, stress‐adaptive traits can be divided into groups whose genes and/or physiological effects are likely to be relatively independent such that when parents with contrasting traits are crossed, adaptive genes will be pyramided. Currently the following groups of candidate traits are being considered for drought adaptation in wheat: traits relating to: (i) pre‐anthesis growth, (ii) water extraction, (iii) water use efficiency, (iv) photo‐protection. A number of mechanisms relating to root function have potential to ameliorate drought stress. Hydraulic redistribution (HR) of water by roots of dryland shrubs enables even relatively small amounts of rainwater to be moved down into the soil profile actively by the root system before it evaporates from the soil surface. Another example is the symbiotic relationship of plants with mycorrhizal fungi that produce a glycoprotein that has a positive effect on soil structure and moisture characteristics. From an agronomic point of view, crop water use efficiency can be increased by exploiting the stress‐adaptive mechanism whereby leaves reduce transpiration rate in response to a chemical root signal in response to drying soil. While there is limited genetic diversity for adaptation to salinity in wheat, tolerance has been found in the ancestral genomes of polyploid wheat and their relatives associated with sodium exclusion into the xylem. Wide crossing techniques such as production of synthetic hexaploids are being exploited to tap into this source of genetic diversity. Looking further into the future, progress is being made into understanding the regulatory mechanisms that are expressed under abiotic stress to maintain cellular homeostasis, as well as in the ability to genetically transform crop plants with genes from alien species.