利用基因工程菌VG1(pTU14)产聚β-羟基丁酸酯的研究

本文对透明颤菌血红蛋白基因 (vgb)和λ噬菌体裂解基因 (S RRz)在不同宿主大肠杆菌中的外源表达及其在聚β 羟基丁酸酯 (PHB)生产中的应用进行了研究。实验结果表明 ,同时携带vgb、S RRz和 phbCAB三种基因的产PHB基因工程菌VG1 ( pTU1 4) ,经过 82h的摇瓶补料分批培养 ,菌体浓度可以高达 2 5 9g/L ,PHB百分含量则可在 52h时达到 95%以上 ;此外 ,该菌株不仅可以实现摇瓶高密度发酵培养和PHB产品的大量积累 ,还可以同时实现菌体细胞的可诱导裂解破壁 ,因此是一株具有潜在工业应用价值的多功能PHB生产菌株。     

一株可降解聚β-羟基丁酸酯的真菌

随着全球性“白色污染”的日趋严重和人类对改善自身生存环境意识的日益增强,人们在寻求可与环境同化的高分子材料——生物可降解塑料,取代不能生物降解的塑料,消除“白色污染”。聚(-羟基丁酸酯（PHB）是由生物发酵获得的一种可生物降解的脂肪族聚酯,它除了具有高聚物的基本性质外,其可生物降解性和生物相容性倍受人们关注。因此,PHB作为一种新型的可生物降解高分子材料具有广泛的应用前景。然而,PHB的生物降解特性有其自身的特殊性。首先,PHB作为胞内碳源和能源贮存物,在细胞内易于被本身产生的胞内酶降解。但将其从细胞内…     

利用基因工程菌VG1(pTU14)产聚β-羟基丁酸酯的研究

本文对透明颤菌血红蛋白基因(vgb)和λ噬菌体裂解基 因(SＲＲz)在不同宿主大肠杆菌中的外源表达及其在聚β羟基丁酸酯(PHB)生产中的应用进行了研究。实验结果表明,同时携带vgb、SＲＲz和phbCAB三种基因的产PHB基因工程菌VG1(pTU14),经过82h的摇瓶补料分批培养,菌体浓度可以高达25.9g/L,PHB百分含量则可在52h时达到95%以上;此外,该菌株不仅可以实现摇瓶高密度发 酵培养和PHB产品的大量积累,还可以同时实现菌体细胞的可诱导裂解破壁,因此是一株具有潜在工业应用价值的多功能PHB生产菌株。     

利用光合细菌生产聚-β-羟基丁酸酯的研究进展

石油基塑料进入环境后会造成污染并影响人体健康.因此,寻找石油基塑料的替代品成为未来发展的趋势.生物塑料因其具有良好的生物降解性与安全性,近年来备受关注,尤其是作为生物塑料之一的聚-β-羟基丁酸酯(Poly-β-Hydroxybutyrate,PHB),已成为生产生物塑料制品的重要来源.光合细菌(Photosynthet...     

真养产碱杆菌积聚-β-羟基丁酸发酵条件的研究

igenes eutrophus培养过程的研究表明,氮源的限制或缺乏可刺激细胞大量积累聚-β-羟基丁酸(PHB),但PHB合成期氮源的完全缺乏,会导致细胞的PHB合成速率迅速下降;氧的限制也可刺激A.eutrophus合成PHB,但胞内PHB的积累量远小于氮源控制下的情况。在细胞的不同生长期限制氮源的供应会明显影响PHB的发酵过程,当残留菌体浓度达到20g/L至30g/L时停止流加氨水,可以得到较好的发酵水平,细胞干重,PHB含量和PHB浓度可分别达到61.9g/L、80.5%和49.0g/L。     

开放条件下高聚β-羟基丁酸酯含量的甲烷氧化混合菌群的富集

目的:在开放条件下以甲烷为底物富集高聚β-羟基丁酸酯(PHB)含量的甲烷氧化菌群,获得能够利用低成本碳源高产PHB的菌种。方法:采用丰盛-饥饿模式间歇供料,以甲烷为底物,好氧开放式培养甲烷氧化混合菌群,利用苏丹黑染色法动态检测丰盛和饥饿阶段胞内PHB含量的变化,以此为基础考察丰盛-饥饿期比例对富集高PHB含量的甲烷氧化菌群的影响。结果:丰盛-饥饿期比例为1∶3时,微生物PHB含量从17.7%增加到35.5%,且开放培养过程中菌群结构稳定。结论:通过丰盛-饥饿模式间歇供料开放式培养所得的高PHB含量的稳定的甲烷氧化菌群,具有工业生产PHB的应用价值。     

产聚β-羟基丁酸酯菌株的筛选及发酵条件的优化

作为一类可望替代传统塑料的新型可降解生物高分子材料,聚β-羟基丁酸酯(PHB)日益引起人们的重视。采用尼罗蓝荧光法从污水中初筛得到产PHB的细菌,摇瓶发酵复筛得到一株PHB产量较高的菌株AE13,同时对该菌株的发酵条件进行了正交优化,PHB的产量达到0.85g/L。     

聚β-羟基丁酸酯解聚酶相关性质的研究

从不同环境和地域的活性污染泥中分离筛选出3种可降解聚β－羟基丁酸酯（PHB）的菌株,编号分别为DS9701、DS9710和DS9713。对其所产生的PHB解聚酶的相关性质进行了研究。3种菌株产所产生的PHB解聚酶均是胞外酶,同时又都是诱导酶。不同蓖株分泌PHB解聚酶的规律不同,但酶活力达到高的时间均为96h。3种粗酶液的表观最适反应温度为40℃－45℃,对粗酶液的最适反应pH也进行了表征。     

尼罗蓝在筛选PHB高产菌株中的应用研究

建立一种简便、高效、可靠的初筛方法是PHB高产菌株筛选的关键。以芽孢杆菌(BacillusP-9)为试验材料,对各种PHB产生菌筛选方法进行了比较,最终确定尼罗蓝染色法为一种最佳方法。并且对试验程序进行了优化,确定尼罗蓝染液的最佳浓度为0.225mg/L,菌株的最佳染色时间为培养后96h。进一步证实了尼罗蓝染色法为一种值得推广的PHB产生菌初筛方法。     

我国聚β—羟基丁酸的研究进展与展望

聚采β-羟基丁酸（PHB）是细菌细胞内积累的一种能被微生物的酶所降解的一种高分子聚合物,作为细胞内的能源和碳源物质。介绍了PHB的特性和应用情况。PHB的合成机理和主要技术方法,我国PHB的研究进展和展望等。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

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.