枯草杆菌(Bacillus subtilis)蛋白酶突变株蛋白酶和α-淀粉酶合成的关系

用同步辐射、离子注入和紫外辐射对枯草芽孢杆菌(Bacillus subtilis)183l菌株辐射诱变后,筛选到四个稳定的蛋白酶突变株。研究了B．subtilis 183l亲株及其蛋白酶突变株的蛋白海和α-淀粉酶合成情况,分析了蛋白酶和α-淀粉酶的合成关系。结果表明,B． subtilis 183l亲株及其突变株在以豆饼粉、玉米粉、麸皮等组成的发酵培养基中,37℃,120r／min培养条件下,各菌株最高α-淀粉酶活力相差不大;中性蛋白酶与α-淀粉酶的合成可能具有相互促进的作用。     

河内白曲霉酸性α-淀粉酶高产菌株的诱变选育

采用不同浓度的硫酸二乙酯(DES)诱变处理萌发的河内白曲霉孢子,后涂布于筛选培养基,根据透明圈大小初筛高产酸性α-淀粉酶的突变株,并进行摇瓶复筛。结果表明:将萌发的河内白曲霉孢子于1%DES处理20 min,致死率为84.3%,后涂布筛选获得一株高产酸性α-淀粉酶的突变株Hanoi white starter 4,发酵后酶活力达20.8 U/g,比野生菌株提高了61.2%,且遗传稳定性良好。     

耐酸性α-淀粉酶高产菌株的选育

从酒曲中筛选得到1株高产耐酸性α-淀粉酶的野生菌株Tx-78,经鉴定为曲霉属的黑曲霉(Aspergil-lus niger)。以Tx-78作为出发菌株,通过紫外线(UV)诱变和亚硝基胍(NG)诱变,获得了遗传稳定的高产菌株UN78358,其产酶量可达到1 120 U/mL。     

米曲霉尿嘧啶营养缺陷型突变体筛选及转化体系建立

米曲霉(Aspergillus oryzae)是一种十分重要的工业微生物，但由于其菌丝体和孢子均含有多个细胞核，并且对多种抗性药物具有抗性，导致其遗传转化和分子生物学研究较其他模式丝状真菌困难。目前米曲霉遗传转化主要采用营养缺陷型作为筛选标记。尿嘧啶营养缺陷型是米曲霉转化中最常用的一种营养缺陷型标记，其筛选标记基因pyrG编码乳清酸核苷-5′-磷酸脱羧酶为尿嘧啶的前体尿苷合成所必需。本研究以米曲霉3.042为背景，利用紫外线诱变和5-氟乳清酸(5-FOA)胁迫筛选获得5株尿嘧啶营养缺陷型菌株，经DNA测序5株菌株均为pyrG基因不同位点突变，确定为尿嘧啶营养缺陷型。以筛选到的尿嘧啶营养缺陷型菌株为背景，利用农杆菌介导的米曲霉转化系统，成功构建了米曲霉尿嘧啶营养缺陷型为筛选标记的农杆菌转化体系。     

中性蛋白酶高产菌株的筛选及产酶酶系分析

目的:满足水产中对中性蛋白酶的需求。方法:以实验室保藏的米曲霉ZW为出发菌株,经Co60定向诱变,通过透明圈法初筛、摇瓶发酵复筛,筛选中性蛋白酶活力高的菌株,并对其进行产酶酶系分析。结果:筛选到的米曲霉ZW-06产中性蛋白酶酶活可达15000U/g干曲,比诱变前酶活提高了74%,是目前国内报道的固体发酵产中性蛋白酶活力最高的菌株;经过10代传代之后,酶活力仍保持稳定。通过对米曲霉ZW-06进行产酶酶系分析,发现发酵产物中除了有较高的中性蛋白酶酶活,还有较高的木聚糖酶和酸性纤维素酶酶活,酶活分别达到49879U/g干曲和21099U/g干曲。结论:米曲霉ZW-06在饲料工业中有很大     

产氨基酰化酶米曲霉高产菌株的选育

采用亚硝基瓜抑菌圈法对米曲霉菌株3042,AF92011,AF93018,AF93020,AF93022,AF93332进行诱变处理,从诱变菌株中筛选到几个高产氨基酰化酶菌株(3042-5,AF93020-2,AF93020-6和AF93022-5),对DL-蛋氨酸的拆分活力分别比出发菌株提高34.1%、157.6%、152.4%和145.4%,其中米曲霉菌株3042的诱变菌株3042-5最高酶活力达203.1U/ml     

耐低温淀粉酶产生菌Y89微波诱变及发酵工艺

为进一步提高耐低温淀粉酶产生菌的发酵生产水平,以前期筛选得到的1株耐低温兼性厌氧淀粉酶产生菌Y89为出发菌株,对其进行微波诱变处理,通过酶产量及遗传性能稳定检测筛选高活力突变株,并采取单因素优化法对菌株的培养基和培养条件进行优化。获得1株遗传稳定的高活力突变株Y89-11,淀粉酶产量达750.2 U/m L,是原出发菌株的1.94倍。采用单因素实验确定该突变株的最佳发酵条件:最适生长及产酶温度为16℃,最佳产酶时间60 h,最优碳源为可溶性淀粉,氮源为酵母膏,培养基中添加Ca2+可显著提高产酶量。经诱变选育出的突变株Y89-11与原菌株相比产酶量提高了94%,所产淀粉酶为中低温酶,最适反应温度30℃,耐低温效果较好,应用前景广阔。     

热稳定β—淀粉酶高产菌株选育及发酵条件研究

从土壤中分离得到一株高温放线菌V_4菌株(Thermoactinomyces sp.V_4),经测定能产生热稳定β-淀粉酶。V_4菌株经过热诱变获得一株具高活力β-淀粉酶的变异株A_(61),产酶活力从400u/ml提高到1000u/ml。A_(61)菌株产生的β-淀粉酶最适反应温度为60℃,酶的热稳定性良好,50℃保温4小时不失活,55℃保温2小时仍具有最初活力的96％。     

丝状真菌表达分泌系统中受体菌的构建

黑曲霉糖化酶高产菌株T21经紫外诱变后, 通过酪蛋白平板和蛋白酶活性测定筛选出胞外酸性蛋白酶活力仅为原株076%的菌株A.nigerT21-201,其生长特性和产糖化酶活力与原株基本一致。利用原生质体PEG法将含有报告基因vhb的表达分泌质粒Pgt10-vhb通过与选择标记质粒的共转化导入此蛋白酶部分缺陷株及其原株T21,检测在蛋白酶缺陷株Aspergillus niger T21-201 和原株T21中VHb的分泌表达,结果表明在A.nigerT21-201中VHb表达水平显著高于原株,但Northern blot却显示在两菌株中^vnb基因的转录水平近似,由此证明酸性蛋白酶缺陷对保护外源蛋白产生了显著效果。      

高产Monacolin K纯种红曲培养条件的研究

本实验对已有的十株红曲霉菌株进行纯种制曲,筛选出一株生长良好、Monacolin K含量高、不产桔霉素、产色素能力强及糖化酶活力相对较高的红曲霉菌株.以大米为原材料,采用液固联合制曲法,通过单因素实验对纯种红曲的培养条件进行优化.结果表明,固体培养基初始含水量为45％,接种量为8％,变温培养红曲时,红曲霉M-7所得纯种红曲最佳,其Monacolin K含量高达243 μg/g,色价450 U/g,糖化酶活力4 289 U/g.与优化之前比较,Monacolin K含量提高了37.2％.     

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.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

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.