极地和深海环境中低温噬菌体研究进展

极地和深海是地球上较为独特的生态系统,生活在其中的生物由于长期处于低温、寡营养和黑暗封闭的环境中,大多缺乏基本的光合作用,而被认为是研究生命进化和地球环境演化等问题的＂活化石＂。在这样的极端环境中,低温噬菌体的丰度却很高,越来越多的证据表明它们在维持这类环境的生态平衡和调控生物地球化学循环等方面扮演着非常重要的角色。对极地与深海中低温噬菌体的研究进行简要综述。     

干旱对湖北省长湖水生植物多样性的影响

将断面法和地理信息系统（GIS）与全球定位系统（GPS）技术相结合,通过比较湖北省长湖2000年（干旱年）与1999年（非干旱年）的水生植物多样性,探讨了干旱对淡水湖泊水生植物多样性的影响,主要结论如下：（1）干旱对长湖淡水湖泊水生植物物种多样性无影响,但可增加优势种数目（从12个至14个）。（2）干旱使长湖水生植物群丛数目从14个增加至18个,且能显著提高各群丛的Simpson与Shannon-Wiener物种多样性指数。（3）干旱显著提高了长湖水生植被覆盖率与各群丛的盖度,并使全湖水生植被平均单位面积生物量与各群从单位面积生物量显著升高。（4）在干旱年（2000年）,长湖挺水植被消失,但浮水植被面积与沉水植被面积显著扩大：分别从1999年的3.71％与41.32%上升至2000年的12.63%与53.84%（占湖泊总面积的百分比）。（5）干旱条件下淡水湖泊水生植物的生长发育明显加快：2000年7月菹草石芽萌发率、菹草幼株长度和野菱黄叶率显著高于1999年同期值。     

噬菌体治疗研究进展

噬菌体发现之初, 便被前苏联和东欧医学界用来治疗细菌感染。但是, 随着抗生素时代的到来, 人们慢慢忽略了对噬菌体的深入研究。近来, 由于全球耐药菌感染率不断攀升, 用抗生素治疗细菌感染面临了前所未有的挑战, 一些科学家和临床工作者开始重新把注意力集中到噬菌体研究上来, 并在这个领域取得了极大的进展, 尤其是通过大量的实验证明: 噬菌体可以有效地提高细菌感染的实验动物的存活率。本文就近几年国内外的科研工作者在噬菌体治疗领域所取得的进展做一综述。     

一株黄杆菌低温噬菌体的生物学特征研究

目的 对分离自明永冰川地区的1株黄杆菌噬菌体（SWP-8）生物学特性进行研究。方法 利用透射电子显微镜（TEM）技术及氯化铯密度梯度离心法对SWP-8进行形态观察、基因组酶切片段长度多态性分析及噬菌体生理特性研究。结果 噬菌体SWP-8为肌尾型,在电镜下呈头尾复合型结构,头部呈正多面体立体对称,直径约150 nm;尾管长约150 nm,直径约20 nm,具有收缩性的鞘,头部与尾管结合处具有颈环结构。在4 ℃时具有感染性,4～25 ℃均能产生边缘清晰、透明的噬菌斑。pH值耐受范围较广,最适pH值为7.0。最佳感染复数为10.000,潜伏期60 min,裂解期90 min,裂解效率较高。结论 SWP-8属肌尾噬菌体科（Myoviridae）,是裂解性噬菌体,对氯仿和蛋白酶K较为敏感。基因组为dsDNA,大小约为75 kb。     

三种致病性耶尔森氏菌噬菌体的分离鉴定研究进展

3种致病性耶尔森氏菌包括鼠疫耶尔森氏菌、假结核耶尔森氏菌和小肠结肠炎耶尔森氏菌,其噬菌体可用于耶尔森氏菌的诊断、防治和生态进化学研究。本文重点分析3种致病性耶尔森氏菌噬菌体的分离鉴定史。将3种耶尔森氏菌噬菌体基因组进行比较分析,并对各菌的噬菌体受体进行总结,为研究及利用3种耶尔森氏菌噬菌体提供思路。     

湖泊微生物多样性研究进展

随着不依靠培养的分子生物学技术的迅速发展,湖泊微生物多样性研究越来越受到人们的重视并取得了较大的成果.从从古细菌域、细菌域、真核生物域3个方面概述了湖泊微生物多样性的研究进展并简单介绍了宏基因组技术在湖泊微生物多样性研究中的运用.     

噬菌体抗体库技术研究进展

抗体研究可分多克隆抗体、单克隆抗体和基因工程抗体三个阶段。特别是噬菌体抗体库 (ｐｈａｇｅａｎｔｉｂｏｄｙｌｉｂｒａｒｙ)技术[1 ]可达到不经免疫制备人源性小型化基因工程抗体。这一技术将抗体基因的克隆与表达融为一体 ,是一种新的基因操作技术 ;同时将识别抗原与再扩增能力结合在一起 ,是一种高效的表达和筛选抗体的新一代技术。1　噬菌体抗体库技术的基本原理[2 ,3 ]噬菌体抗体库技术是将抗体ＶＨ和ＶＬ基因与噬菌体的外壳蛋白Ⅲ (ｃｐⅢ )或Ⅷ (ｃｐⅧ )基因随机重组 ,继而感染大肠杆菌 ,经增殖并在噬菌体表面以抗体片段Ｆａｂ…     

自然环境中T4型噬菌体g23基因多样性研究进展

摘要：过去的20多年,伴随着分子生物学技术在环境微生物研究中的应用,环境中细菌和真菌群落基因多样性及与其生存环境间的关系逐渐被揭示,但对于地球上广泛存在且数量巨大的生命体-噬菌体基因多样性研究还很少。本文以编码T4型噬菌体主要壳蛋白基因g23为目标,综述了近年来T4型噬菌体在海洋、湖泊和稻田中基因多样性的研究进展。研究结果表明T4型噬菌体g23基因分布与其生存环境关系很大,许多g23基因按获取环境不同划分为几个新类群。同时文中也指出了针对环境中T4型噬菌体g23基因研究应该注意的几点问题及未来的研究发展趋势。     

类杆菌噬菌体研究进展

随着厌氧培养技术的发展和完善,人们逐渐认识到厌氧菌在临床细菌学中占有重要地位。本文就临床上最常见的厌氧菌－类杆菌噬菌体的分离方法,基本特性,形态特点,溶原性,分型鉴定的可能性等作一综述。     

辅助噬菌体在噬菌体展示中的应用及研究进展

噬菌体展示技术是一种将外源肽或蛋白质与特定噬菌体衣壳蛋白相融合,展示于噬菌体表面来构建蛋白质或多肽文库,并从中筛选目的蛋白、多肽或抗体的基因工程高新技术。噬菌粒/辅助噬菌体系统是最常用的噬菌体展示系统,此系统中辅助噬菌体对噬菌粒的复制和组装发挥着至关重要的作用。本文结合当今该领域的最新研究动态,概述了噬菌粒和辅助噬菌体双基因组系统,着重介绍了不同辅助噬菌体的特点及其突变机制,并对其应用前景进行了展望,以期为该技术的进一步完善提供一定的借鉴作用。     

海洋微生物多样性研究技术进展

海洋微生物资源丰富,开发潜力巨大,综述了稀释培养、高通量培养、扩散盒培养和微囊包埋等新的海洋微生物可培养技术的发展,重点阐述了基于现代分子技术的PCR、DGGE/TGGE、gyrB基因、基因芯片、环境基因组学和质谱等方法在未培养海洋微生物多样性研究中的应用。通过上述研究技术和方法的创新,人类开发海洋微生物资源进入一个崭新的时代。     

Biomass diversity and stability of food webs in aquatic ecosystems

The diversity–stability hypothesis in ecology asserts that biodiversity begets stability of ecological systems. This hypothesis has been supported by field studies on primary producers in grasslands, in which the interaction between species is mostly competition. As to ecosystems with multitrophic predatory interaction, however, no definite consensus has been arrived at for the relation between trophic diversity and ecosystem stability. The stability index suitable to ecosystems with predatory interaction is given by MacArthurs idea of stability and its formulation by Rutledge et al. More suitable indices of stability (relative conditional entropy) are proposed in this study for the comparison of different ecosystems, and the validity of the diversity–stability hypothesis for food webs (networks of predation) with many trophic compartments in natural aquatic ecosystems is examined. Results reveal that an increase in the biomass diversity of trophic compartments causes an increase in the whole systemic stability of food webs in aquatic ecosystems. Hence, evidence of the whole systemic validity of the diversity–stability hypothesis for natural aquatic ecosystems with ubiquitous multitrophic predatory interaction was obtained for the first time.     

Patterns and governing forces in aquatic microbial communities

In this review we survey recent publications employing molecular techniques to investigate the distribution of microbial species in aquatic environments. We analyzed the occurrence of microbial phyla in freshwater and marine habitats and observed patterns of distribution that could be explained by the adaptation of microorganisms to physical and biological parameters that vary in aquatic habitats. The gram-positive bacteria, the Verrucomicrobiales and the - and -subdivisions of the Proteobacteria are distributed throughout a range of aquatic habitats, while other phylogenetic groups appear to be adapted to more narrowly defined environmental niches such as anoxic water and sediments (-Proteobacteria) or floating aggregates (Cytophaga-Flexibacter-Bacteroides phylum). -proteobacterial sequence types have been detected throughout freshwater habitats, but these organisms are largely absent from open ocean environments. Within several of these divisions, clusters of closely related small sub unit ribosomal RNA sequence types have been detected in geographically disparate environments, suggesting that some microbial species are globally distributed. In addition to physical variables such as salinity and pH, biological variables also influence microbial community composition. This was illustrated by changes that occurred in the eukaryotic and bacterial species composition in laboratory mesocosms after a viral outburst. We conclude that physical and biological forces govern the composition of aquatic microbial communities and result in divergent evolutionary histories of the indigenous microbial species.     

Genetic structure of natural populations of Nitrobacter in an aquatic environment

Nitrification has been essentially studied as a chemical process and the studies of the microbial population have been slightly worked out. This work constitutes a first attempt to study the diversity of Nitrobacter strains with the aim of working out the genetic structure of natural populations. The Nitrobacter population structure was compared between freshwater and sediments of the same lake. Nitrobacter isolates were identified and characterized by DNA/DNA hybridization, restriction pattern of rRNA genes, PCR/RFLP analysis of the ribosomal intergenic spacer and plasmid patterns. It was shown that this lake population was split into 3 subpopulations: a specific freshwater subpopulation, a specific sediment subpopulation and a nonspecific one. A 60 MDa plasmid was detected in 3,3% of freshwater isolates. A 37 MDa plasmid was detected in 59% of sediments isolates. This 37 MDa plasmid was not associated with a genomic group, but associated with a localization: the sediments. These results suggest that this 37 MDa plasmid could be implicated in the adaptation to sediment environment.     

Island biogeography, diversity and dominance of zooplankton in crater lakes on the Azores

In July and August 1988 samples of zooplankton were collected from 17 lakes on four islands. Five species of Cladocera, three species of Copepoda and 30 species of Rotifera were found. The maximum numbers of species in any one lake were four planktonic Cladocera, two Copepoda and seven planktonic Rotifera (with up to six additional non-planktonic species). The smallest, most distant island had fewer species than the largest island nearest to the mainland, but the number of species in each lake was determined more by the size of the lake than by its location. This results in the most distant island having lakes containing the same number of species as lakes of similar size on islands nearer to the mainland. The numbers of zooplankton species in each of these lakes are significantly lower than the world average, and the dominance ratios are significantly higher.     

低温脂肪酶产生菌的筛选、产酶发酵及粗酶性质研究

利用含有Tween 80的琼脂平板和摇瓶发酵法,从若尔盖高原土壤中筛选产脂肪酶菌株.通过菌落形态和菌体特征观察初步对菌种进行鉴定,得到一株产低温脂肪酶的适冷菌Pseudomonassp.DL-B,并设计正交试验对该菌株的产酶发酵培养条件进行了优化.摇瓶实验表明,该菌株最适产酶发酵培养基为:蔗糖10 g/L,蛋白胨20 ...     

淡水水生植物化感作用研究进展

水生植物的化感作用对淡水生态系统中水草的可持续管理和湖泊富营养化的生态控制具有非常重要的意义。本文综述了淡水水生植物化感作用的发展历史和研究现状,讨论了水生植物化感作用研究过程中所涉及的实验方法、生物测试方法、化感物质分离方法以及影响水生植物化感研究的环境因素。抑藻圈试验、藻类生长试验和浮萍生长试验是常用的生物测试方法;采用共生培养或单独培养的方法,从种植水中分离、鉴定化感物质,对证实复杂水环境中水生植物化感作用的存在,研究它们化感物质的释放途径和作用机理都具有十分重要的作用。