产胞体木聚糖酶放线菌的分离与筛选

报道了产胞外木聚糖酶放线菌的筛选方法,实验表明ＰＨ６．０±０．５可用作一般放线菌木聚糖酶活力测定的酸碱度。     

木聚糖酶高产菌株Bacillus pumilus H—101的筛选及产酶条件的研究

从34株细菌中筛选到一株木聚糖酶高产菌株BacilluspumilusH－101。适宜的产酶培养基含2．0％小麦秸半纤维素、0．2％（NH4）2SO4、0．1％NH4NO3、0.1％K2HPO4、0．01％MgSO4·7H2O、0.02％NaC1、0.02％CaCl2·2H2O和1.0％的酵母膏。在上述培养基中,32℃振荡培养48h,总半纤维素酶活力达235．6u／ml,木聚精酶活力达1164．2u／ml酶反应的最适温度为50℃,最适酸碱度为pH6．5;Na 、Mg2 等离子可提高木聚精酶的水解活性,而Zn2 、Cu2 等离子则对木聚糖酶活性有明显的抑制作用。     

一株产木聚糖酶的黑曲霉固态发酵产酶性质的研究

目的：选育产木聚糖酶活力高的黑曲霉菌株,对其产酶条件进行优化,并研究其酶学性质。方法：通过木聚糖酶解木聚糖产生透明圈的方法,筛选产木聚糖酶菌株,测定固体发酵培养基中玉米芯与麸皮的比例、培养温度、培养时间、添加氮源对产酶的影响。进行了作用温度、pH值、金属离子对酶活力的影响试验,以及酶不同温度下的热稳定性的试验。结果：从自然界筛选得到一株产木聚糖酶的黑曲霉菌株,通过对固态发酵培养条件优化,最终产酶水平达到了5500u／g固体干曲。酶的最适作用温度是45℃、最适作用pH值4．8,是一种偏酸性酶。该酶在45℃以上的温度保存会使酶活力迅速丧失,Mg^2＋、Zn^2＋对该酶有激活作用,而Mn^2＋、Cu^2＋、Hg^2＋则完全抑制酶的活性。结论：选育的黑曲霉菌株产木聚糖酶活力较高,培养条件简单。     

耐热过氧化氢酶产生菌的筛选和发酵条件的研究

从59株嗜热放线菌中筛选出一株产胞外过氧化氢酶活力较高的嗜热链霉菌(Thermo-sueptomyces sp．)T485。其产酶的适宜条件为培养温度50℃,培养基pH6—8,碳源麦芽糖,氮源酵母膏,250ml三角瓶装30—50ml培养基,振荡培养48h,产酶可达140u／ml。     

链霉菌Strz-2胞外木聚糖酶的纯化和固定化研究

为探讨木聚糖酶被固定化后的酶活力变化 ,采用盐析、离子交换和分子筛层析方法对链霉菌胞外木聚糖酶进行了纯化 ,并采用DNS方法对固定化酶的性质进行了研究。结果如下 :粗酶液被纯化了 30 .5倍 ,比活力达 4 5 7.5 ,活力回收 4 2 .6 %。纯化后的酶固定在戊二醛交联的壳聚糖上 ,残活力为 4 1.8%。固定化酶的最适pH为 6 .0 ,最适温度为 5 5℃ ,且固定化酶在 6 5 -75℃活力都较高。该酶的耐热性比较强 ,固定化酶热稳定性优于原酶 ;以木聚糖为底物 ,固定化酶的表观米氏常数为 0 .83× 10 -2g/L。因此 ,固定化的木聚糖酶优于原酶     

产木聚糖酶的沿海红树林真菌筛选及其培养与酶活测定条件优化

从香港海岸红树林分离到的 77株真菌中有 34株可产生木聚糖酶 ,从中选出CY2 80 9(Staganosporasp .)、CY4 786和CY5 0 4 0等 3菌株与已知陆生产酶菌株HU5 0 4 8(Aspergillusawamori)进行产木聚糖酶的比较研究。根据培养液中菌丝生物量、木聚糖酶活力和木糖等价还原糖含量等指标的测定 ,菌株CY4 786在起始pH 7 8的木聚糖 酵母膏 海盐液体培养基中 2 5℃下震荡 (10 0r min)培养 7d产酶最佳 ;粗酶液在 5 0℃和pH 4 6的优化条件下进行测定 ,木聚糖酶活力达到 1 0 7× 10 4 U mL。结果表明 ,红树林真菌起着半纤维素降解者的作用 ,沿海红树林环境中存在着可资利用的木聚糖酶产生菌。作者讨论了利用发酵液中木糖等价还原糖含量的动态变化作为快速筛选产木聚糖酶菌株的指标的可能性     

链霉菌产木聚糖酶条件和酶学性质以及重离子诱变对产酶的影响研究

以一株由青藏高原牦牛粪中分离出的链霉菌为出发菌株,对其培养特性、产酶条件和酶学性质进行初步研究.通过重离子诱变,筛选出遗传稳定的高产菌株.结果表明,该菌以玉米芯和麸皮(1∶1)为碳源能高效地诱导木聚糖酶的胞外分泌,其最适培养基和培养条件氮源为酵母膏、初始pH7、培养温度为25℃,在此条件下,第4天酶活力达到峰值3480.25 U/mL.说明该酶能够利用农业废弃物高效生产木聚糖酶.该菌株所产木聚糖酶的最适反应温度为15℃、pH4,属低温酸性木聚糖酶.经重离子诱变后,筛选出一株高产菌株SZ10-7,其酶活力可达5 338.42 U/mL.     

苯甲酸1，2-双加氧酶高活力菌株的筛选和发酵条件的研究

从176株细菌中,筛选出苯甲酸1,2-双加氧酶的高活力菌株假单胞菌(Pseudomonas)137。进行了该菌产酶的发酵条件试验。产酶的最适温度为32℃,最适起始pH为6．5—7．0。葡萄糖、麦芽糖和甘油对产酶有明显的抑制作用,苯甲酸钠对产酶有促进作用。氨态氮对菌体生长和产酶是必需的。琥珀酸钠是酶形成的有效诱导物,采用0．1％苯甲酸钠和0．2％琥珀酸钠培养基(pH6．5—7．0),于32℃振荡培养72小时,可获得高活力的苯甲酸1,2-双加氧酶,每克菌体酶活力可达5-8单位。     

牦牛源木聚糖酶产生菌的筛选和鉴定

目的以牦牛粪便为样本,筛选并鉴定产木聚糖酶菌株。方法利用碱提取法从玉米芯中提取木聚糖,以自制木聚糖为唯一碳源,从牦牛牛粪中筛选产木聚糖酶细菌,利用16S rDNA基因序列分析鉴定菌种,3,5-二硝基水杨酸法(DNS)测定其产酶能力并分析所产酶的酶学特性。结果筛选获得牦牛源产木聚糖酶类芽胞杆菌,所产木聚糖酶的最适反应条件为50℃、pH 8.0,在pH值为7.0或8.0以及温度50℃条件下,表现出较好的稳定性,Mn~(2+)对酶活力具有显著抑制作用,该菌最佳发酵时间为12 h,酶活最高达到1.2 U/mL。结论该菌所产木聚糖酶能够针对性地降解玉米芯木聚糖,在畜牧业和工业上有一定的应用价值。     

一株产木聚糖酶链霉菌的鉴定及发酵产酶*

以木聚糖为唯一碳源,筛选出一株高产木聚糖酶生产菌株。该菌株经形态特征、 培养特征、生理生化和细胞壁组分分析等实验,鉴定为卷须链霉菌（Streptomyces cirratus).摇瓶发酵产酶实验表明：培养基最佳初始pH值为6．0;玉米芯水不溶木聚糖和蛋白胨分别是最佳的碳源和氮源;添加0．5％吐温80使得木聚糖酶活力提高到原来的2．5倍,发酵液最高酶活达到623u／mL。     

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.