阿维菌素B1a组分高产菌株的诱变育种

目的了解阿维菌素产生菌S.avermitilis的生长特性,提高产生菌B1a组份的产量。方法采用紫外线(UV)、诱变剂氯化锂(LiCl),亚硝基胍(NTG)并结合甲硫氨酸(Met)诱导等手段对出发菌株S.avermitilisH0065进行诱变处理,初筛、复筛。结果筛选获得总效价达到4524.3μg/ml的高产阿维菌突变株N-3-133,其中B组分含量显著提高且高达85.3%,B1a也显著提高达到2533.6μg/ml。结论采用紫外线及亚硝基胍诱变方法,结合甲硫氨酸诱导筛选,与出发菌株相比可以获得阿维菌素总效价及B1a组分显著提高的菌株。     

阿维链霉菌的诱变育种

以阿维链霉菌(Streptomyces avermitilis)76-12为出发菌株,采用亚硝基胍、吖啶橙、紫外线和氯化锂分别对其孢子和原生质体进行诱变,经抗代谢物理性筛选,获得一系列高产突变株,其中N-1-2高产突变株的发酵单位是出发菌株的2.47倍。实验中同时获得了只产阿维菌素a组分的突变株G-32、Bla组分含量高的Ave8菌株和产蓝绿色孢子的突变株UA-G等。     

L—赖氨酸高产菌株选育的研究

L-赖氨酸产生菌钝齿棒杆菌（Corynebacteriumcrenatum）N30－25菌株经紫外线诱变处理,分别在含有不同浓度的七叶苷的培养基上进行筛选,经摇瓶多次复筛获得了3株高产变异菌株。对这3株菌在相同发酵条件下进行发酵生产L－赖氨酸,与出发菌株比较,产量提高了22－31％,经过3次传代,产生L－赖氨酸能力仍很稳定。     

阿维莲霉菌中aveD基因缺失对阿维菌素合成的影响

利用aveD基因的缺失载体pCZ8(pKC1139::△aveD)对阿维菌素（Avermectin）的产生菌阿维链霉菌（Streptomyces avermitilis)76-9的aveD基因进行缺失获得aveD缺失突变株。经摇瓶发酵和HPLC检测,发现该突变株只产生阿链菌素B组分。说明将阿维链霉菌的aveD基因缺失,并不影响下游aveF的表达。缺失突变株的阿维菌素的总产量与出发菌株的总产量基本相同,突变株中B1的产量略有提高,阿维菌素B2的含量显著提高。     

南昌霉素高产菌株的链霉素抗性基因突变诱变筛选研究

通过对链霉素对南昌霉素（Nanchangmycin)产生菌NS－41－80菌株孢子的致死浓度测定基础上,采用诱变剂甲基磺酸乙酯（EMS）的不同诱发剂量对菌株孢子进行诱变处理,诱变处理的孢子涂布在含链霉素（10ug/mL)致死浓度的高氏平板上,获得了大量的链霉素抗性基因（str)突变株。然后从3,000株链霉素抗性基因（str)突变株中通过初筛获得比诱变出发菌株产素能力提高20％以上的菌株202株,再进一步通过摇瓶复筛,获得比出发菌株产素能力分别提高100％,200％,300％高产菌株为48株,7株和1株,分别为复筛菌和初筛菌株的23．76％和1．60％,3．46％和0．23％,0．5％和0．03％,将产素能力提高240％以上5个菌株连同出发菌株连续3批次进行摇瓶发酵结果,5个突变株的产素能力均比出发菌株的产素能力提高57％－96．4％,其中突变株80－5．3－165菌株摇瓶发酵单位达6,000ug/mL以上,3批次摇瓶平均发酵单位达5,855ug/mL,建立了南昌霉素高产菌株的链霉素抗性基因突变诱变快速高效的筛选方法。     

阿维菌素衍生物CHC-B1的突变生物合成

利用成功构建的基因缺失载体pLJ04(pKC1139∷△bkdF +△bkdH)对阿维菌素(avermectin)高产菌阿维链霉菌(Streptomyces avermitilis)76-02-e的bkdFGH基因进行缺失,获得的bkdFGH缺失突变株经过摇瓶发酵和HPLC检测,发现该突变株完全丧失了产生阿维菌素的能力。2-甲基丁酸及异丁酸的前体添加试验表明,当有外源前体存在时,突变株又能恢复阿维菌素合成的能力。将该bkdFGH基因缺失突变株命名为S.avermitilis bkd76-3。环己羧酸(CHC)前体添加试验及HPLC检测发现存在4种产物,经LC/MS分析验证,其中两种产物分别为CHC-B1和CHC-A2。     

高产谷胱甘肽的酵母菌选育及其培养条件研究

筛选到一株具有较高GSH产量的酵母菌株S.cerevisiae2165,然后以该菌株为出发菌,采用紫外照射,紫外照射 LiCl联合处理,亚硝基胍（MNNG）等诱变处理,获得一株高产GSH的酿酒酵母优良菌株S.cerevisiaeJN-5-8。该菌株具有稳定的遗传性能,在经过优化的培养条件下培养24h,其GSH产量达到339.1mg/L。比出发菌株提高2.2倍。     

6-巯基嘌呤筛选L-组氨酸产生菌株

目的：为得到L-组氨酸的高产菌株。方法：以谷氨酸棒杆（Corynebacterium glutamicum）S6为出发菌株,利用亚硝基胍进行多次诱变。结果：在6-巯基嘌呤（MP）的抗性梯度平板上挑取正突变菌株,发酵,最终挑出一株N13（MP）,可积累L-组氨酸561mg／L,比出发菌株提高45．34％。结论：利用结构类似物抗性平板御筛选L-his高产菌株是可行的。     

阿维菌素生产菌的常压室温等离子体诱变育种及培养基优化

【目的】通过诱变筛选技术选育阿维菌素高产突变株,对其发酵培养基进行响应面优化,提高阿维菌素产量。【方法】采用常压室温等离子体(ARTP)诱变技术,结合链霉抗性和卡那霉素抗性筛选法及96深孔板高通量筛选法,筛选阿维菌素高产株。在单因素实验的基础上,应用响应面分析法对其发酵培养基进行优化,最后确定最佳培养基配方。【结果】获得一株遗传性状稳定的阿维菌素高产株K-1A6,其阿维菌素产量达到4.22 g/L,比出发菌株9-39提高了23.4%,在最佳培养基中阿维菌素产量达到5.36 g/L,较优化前提高了27.01%。【结论】通过对阿维链霉菌9-39菌株进行ARTP诱变筛选及发酵培养基优化研究能显著提高阿维菌素的产量。     

具有双重抗生素抗性的ε-聚赖氨酸高产菌株选育及生理特性

以ε-聚赖氨酸产量为1.60g/L的Streptomyces albulus M-Z18为出发菌株,利用核糖体工程技术选育具有双重抗生素抗性的ε-聚赖氨酸高产菌株,并对高产菌株和出发菌株的生理生化性能进行比较。通过链霉素诱变成功选育出了1株遗传稳定的ε-聚赖氨酸产生菌S.albulus S-7,ε-聚赖氨酸产量为2.03g/L;对S.albulus S-7叠加巴龙霉素,获得1株遗传稳定的具有双重抗性的ε-聚赖氨酸产生菌S.albulus SP-14,ε-聚赖氨酸产量为2.37g/L,比出发菌株S.albulus M-Z18的ε-聚赖氨酸产量增加了48.10%。使用链霉素和巴龙霉素选育具有双重抗生素抗性的ε-聚赖氨酸高产菌株是一种有效的手段。     

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.