生物合成γ-氨基丁酸曲霉菌株的选育、紫外诱变和发酵条件的研究

从自然发酵的红曲中分离筛选到1株曲霉菌株,其菌丝体可以谷氨酸钠为底物转化富集γ-氨基丁酸(GABA),经初步鉴定该菌株为米曲霉(Aspergillus oryzae)。以该菌株的孢子为对象进行紫外诱变,初筛得到8株产GABA活力不同的菌株,复筛后获1株GABA的产量较高的突变菌株As-8。菌株As-8转化富集GABA的适宜条件为:pH 6.0,以蔗糖为碳源,蛋白胨为唯一氮源或蛋白胨和牛肉膏为复合氮源。产生的GABA含量最高可达4.2g/L,并能稳定遗传。     

高产γ-氨基丁酸酵母菌株的亚硝基胍诱变选育

目的:探讨亚硝基胍诱变选育高产γ-氨基丁酸酵母菌株的方法。方法:使用亚硝基胍对酵母菌株进行诱变;采用含溴甲酚绿的YEPD培养基筛选突变菌,采用薄层层析法和比色法鉴定变异菌株发酵液中的γ-氨基丁酸及其含量;对突变菌株连续继代培养4代,测定各代发酵液中γ-氨基丁酸的含量,鉴定诱变菌株的遗传稳定性。结果:亚硝基胍诱变酵母的最佳浓度为1.0g.L-1,最佳诱变时间为15min;获得了5株突变菌株,菌落呈绿色;薄层层析法鉴定突变菌株都能产γ-氨基丁酸;诱变菌发酵液中的γ-氨基丁酸含量各异,但高于对照,且增长幅度很大;对突变菌株后代遗传稳定性进行了鉴定,结果表明突变菌株4遗传性较稳定。结论:采用1.0g.L-1的亚硝基胍溶液处理酵母菌15min,经筛选鉴定,获得了一株遗传稳定的高产γ-氨基丁酸的酵母菌株。     

一株高效转化Phytosterol为雄甾烯酮菌株的筛选与鉴定

从保藏的200多株菌中筛选出1株高效转化植物甾醇为4-烯-雄甾-3,17-二酮和1,4-二烯-雄甾-3,17-二酮的菌株,并对该菌进行了形态、生理生化的研究。结果发现菌株ST06可以利用多种碳源,可以水解淀粉,但不利用纤微素。用16SrDNA的方法对其进行鉴定,发现与Bacillus属Bacillus amyloiquefaciens的相似性最高,达到99．9％,将该菌株命名为Bacillus amyloiquefaciens ST06。该菌在培养温度30℃,pH7．0,转速220r／min,转化时间7d,底物添加量为0．3％时,ADD与AD的总得率高达40％以上,此时底物转化率高达93．7％。     

生物法制备γ-氨基丁酸过程中细胞的转化特性研究

利用含谷氨酸脱羧酶的细胞转化味精制备γ-氨基丁酸,并测试了该细胞的转化特性。结果显示该细胞最适反应温度为44℃,最适反应pH为4. 6;反应体系中细胞浓度越高,损失的转化活力越低。此外,对反应体系施加外源的真空度,可使细胞转化活力有所提高。5-磷酸吡哆醛是该细胞的必要辅因子,L-谷氨酸可以代替味精作为底物被利用转化成γ-氨基丁酸。     

林生山黧豆中2,4—二氨基丁酸合成代谢的体外酶学研究

用~3H-天门冬氨酸为底物,林生山黧豆(Lathyrus sylvestris L.)叶片匀浆上清液为粗酶液,进行体外反应。结果表明,天门冬氨酸的放射性掺入到2,4-二氨基丁酸,加入谷氨酸则能抑制这种掺入。将上述粗酶液透析,加入可能的辅助因子,天门冬氨酸的放射性也掺入到2,4-二氨基丁酸。研究证实在体外天门冬氨酸可以作为2,4-二基丁酸合成的底物,在林生山黧豆体内存在催化天门冬氨酸转变为2,4-二氨基丁酸的合成酶(系)。以2,4-二氨基丁酸和γ-氨基丁酸为底物,用氨基酸自动分析仪测定产物含量,结果表明,2,4-二氨基丁酸和γ-氨基丁酸不互相转变。     

产γ-氨基丁酸基因工程重组大肠杆菌的构建及其发酵特性

【目的】构建高产γ-氨基丁酸的基因工程重组大肠杆菌（E.coli）,并研究其发酵特性。【方法】首先通过分子生物学方法构建重组质粒pTrc99a-gadB和pTrc99a-gadB-SNO1-SNZ1,然后分别将它们转入基因敲除菌株E.coli ΔgabPΔpuuE/pTrc99a-gadB在含20 g/L底物l-谷氨酸钠的1 L发酵液中的扩大培养结果表明,重组菌培养24 h时,其发酵液中γ-氨基丁酸的含量达到最高值9.4 g/L。【结论】经基因工程构建的重组大肠杆菌产γ-氨基丁酸的能力明显提高,该研究结果为γ-氨基丁酸的产业化生产提供了良好基础。     

离体小麦、向日葵叶片及子叶中γ-氨基丁酸的代谢

离体小麦、向日葵叶片及子叶,在预照光5小时条件下可以利用外源γ-氨基丁酸,形成丙氨酸和谷氨酰胺。小麦叶片中γ-氨基丁酸的脱氨过程主要是γ-氨基丁酸-丙酮酸转氨酶的作用。磷酸钙胶的吸附作用可以将此酶的比活力提高到5.6倍。此转氨酶酶促反应的最适 pH为8.9,在最初反应1小时之内,反应的速度与酶的浓度和反应时间成直线关系,对底物γ-氨基丁酸的米氏常数 Km 为2.6×1~(-3)M。讨论了转氨酶在γ-氨基丁酸代谢中的作用。     

南瓜叶中γ-氨基丁酸的提取及薄层扫描测定

本文在单因素试验基础上,通过正交试验优化了南瓜叶中γ-氨基丁酸的提取条件,并对γ-氨基丁酸的薄层扫描测定方法进行了探索.结果表明,南瓜叶中γ-氨基丁酸的最佳提取条件为:以20％乙醇为溶剂、料液比1∶17(w/v)、提取时间1h,此条件下得到的γ-氨基丁酸的含量为209 mg/100 g.所建立的薄层扫描测定方法在0.125 ～2.0 mg/mL范围内呈良好线性关系(R2=0.9991),平均加样回收率(n=4)为99.61％.     

酵母产γ-氨基丁酸发酵条件的研究

目的：研究酵母产γ-氨基丁酸的发酵条件,提高其产γ-氨基丁酸的能力。方法：以高产γ-氨基丁酸的酵母突变株为材料,通过单因素实验研究培养温度、摇床转速、接种量、种龄和培养时间等条件对菌株发酵生产γ-氨基丁酸的影响。结果：最适发酵条件为：培养温度30℃,摇床转速220 rpm,接种量4%,种龄为2d的种子菌,培养时间4d。在此发酵条件下,变异菌发酵液中γ-氨基丁酸含量高达2.588 g.L-1,较优化前提高了53%。结论：发酵条件的优化,提高了菌株产γ-氨基丁酸的能力。     

酵母产γ- 氨基丁酸发酵条件的研究

目的:研究酵母产γ-氨基丁酸的发酵条件,提高其产γ-氨基丁酸的能力。方法:以高产γ-氨基丁酸的酵母突变株为材料,通过单因素实验研究培养温度、摇床转速、接种量、种龄和培养时间等条件对菌株发酵生产γ-氨基丁酸的影响。结果:最适发酵条件为:培养温度30℃,摇床转速220 rpm,接种量4%,种龄为2d的种子菌,培养时间4d。在此发酵条件下,变异菌发酵液中γ-氨基丁酸含量高达2.588 g.L-1,较优化前提高了53%。结论:发酵条件的优化,提高了菌株产γ-氨基丁酸的能力。     

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.