蛋氨酸高产酵母突变株的推理筛选

以啤酒酵母（Saccharomycescerevisiae）菌株Ⅰ为出发株,经紫外线处理后,在含可完全抑制出发株生长的乙硫氨酸（浓度为2g/L）的基本培养从上筛出14株生长良好的突变株,其中I－2,I－9株还能在无硫基本培养基上良好生长。经氨基酸自动分析仪检测,I－2株菌体蛋白中的蛋氨酸含量（质量由分比）由I株的1．93增年9．28。     

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。     

L-赖氨酸产生菌FH128菌株的研究(Ⅰ)FH128菌株的选育及摇瓶发酵

以赖氨酸产生菌Ａ１１１（ＨＳ－、ＡＥＣｒ）为出发株,经化学诱变剂ＭＮＮＧ（Ｎ－甲基－Ｎ′－硝基－Ｎ－亚硝基胍）及单氟醋酸处理获得单氟醋酸抗性突变株Ｆ７９,摇瓶发酵产Ｌ－赖氨酸盐酸盐７．０％～７．５％,对糖转化率３８％～４０％,分别比Ａ１１１株提高约２５％及２０％。然后,再以Ｆ７９菌为亲株经ＭＮＮＧ及噻唑丙氨酸处理获得噻唑丙氨酸抗性突变株ＦＨ１２８,在适宜的培养条件下,摇瓶发酵产Ｌ－赖氨酸盐酸盐８．５％～９．５％,最高产酸率１１％,对糖转化率４５％～５０％。在１６Ｌ自控发酵罐发酵,产Ｌ－赖氨酸盐酸盐１２％～１４％,对糖转化率４０％～４５％;在２０～１００ｍ３发酵罐发酵,产酸率为８．５％～９．５％,对糖转化率４０％～４２％,提取总收率８０％～８５％,成品（饲料级Ｌ－赖氨酸盐酸盐）质量符合国家标准（ＧＢ８２４５－８７）。ＦＨ１２８菌株遗传性能稳定,营养要求粗放,工艺较简单,便于工业化,二年前已应用于工业生产。     

大剂量紫外诱变选育ε-聚赖氨酸高产菌

以白色链霉菌Z-18为出发菌株,经大剂量紫外诱变处理,用S-2-氨基乙基-L-半胱氨酸（AEC）氨基酸结构类似物平板定向育种方法,获得1株ε-聚赖氨酸高产菌C-18,其发酵液中ε-聚赖氨酸产量较出发菌株提高42．9％。在含有50g／L葡萄糖的培养基中,ε-聚赖氨酸积累可达1．23g／L。     

L-组氨酸高产菌株的选育

为得到L-组氨酸的高产菌株,以谷氨酸棒杆菌（Corynebacterium glutamicum）S9114为出发菌株,利用亚硝基胍（NTG）和硫酸二乙酯（DES）进行多次诱变,在D-组氨酸的抗性梯度平板上挑取正突变株,发酵检测,最终挑出一株S6（D—his＇）,可积累L-组氨酸327mg／L,比出发菌株提高47.3％。     

有益芽胞杆菌受体菌研究

采用酸性茚三酮法测定了30株有益芽胞杆菌的赖氨酸产量,然后在不同的溶菌酶浓度下,对赖氨酸产量超过0.07g/L的21株菌进行原生质体转化质粒pUB110,测定原生质体形成率、原生质体再生率及转化频率,结果6103,6104,6120,6129四株菌的转化频率较高。然后,采用经典遗传学方法选育AEC抗性突变株,使赖氨酸积累提高。其中,B. licheniformis 6104诱变菌株610401能积累赖氨酸2.91 g/L,比出发菌株提高了17倍左右,转化率也提高了一个数量级。通过质粒的再转化试验及传代稳定性试验,进一步证实B.licheniformis 6104及其突变菌株610401是较好的受体菌,尤其是用于赖氨酸合成酶基因的表达。     

紫外诱变原生质体选育赖氨酸高产菌株

以钝齿棒杆菌102S₂-58为出发菌株,在原生质体形成及再生的最佳条件下制备原生质体,并对原生质体进行紫外诱变处理,对大量的再生突变株进行发酵筛选．获得了高产稳定株102－100号,其发酵液经氨基酸自动分析仪测定L－赖氨酸积累量由出发菌株的5O．Omg／ml提高到80．8mg／ml,糖转化率达到63．88％．发酵液中主要副产酸——纈氨酸和蛋氨酸的量明显降低。     

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。     

有益芽孢杆菌受体菌研究

采用酸性茚三酮法测定了30株有益芽胞杆菌的赖氨酸产量,然后在不同的溶菌酶浓度下,对赖氨酸产量超过0．07g/L的21株菌进行原生质体转化质粒pUB110,测定原生质体形成率、原生质体再生率及转化频率,结果6103,6104,6120,6129四株菌的转化频率较高。最后,采用经典遗传学方法选育AEC抗性突变株,使赖氨酸积累提高。其中,B.licheniformis 6104诱变菌株610401能积累赖氨酸2．91g/L ,比出发菌株提高了17倍左右,转化率也提高了一个数量级。通过质粒的再转化试验及传代稳定性试验,进一步证实B.licheniformis 6104及其 突变菌株610401是较好的受体菌,尤其是用于赖氨酸合成酶基因的表达。     

丙酮酸激酶缺陷型黄色短杆菌突变株生成赖氨酸的机制研究

<正> 黄色短杆菌(Brevibacterinm flavum)突变株№.1—231为 S-(2-氨基乙基)-L-半胱氨酸(AEC)抗性、甲硫氨酸敏感性、低活力高丝氨酸脱氢酶(HD)和丙酮酸激酶(PK)缺失的赖氨酸产生菌,由此菌株得到了对甲硫氨酸不敏感的回复突变株,它们有正常的 HD,并有与№.1—231相同的 AEC 抗性和 PK 缺失,但是它们并不比其出发菌株№.15—8产生更多的赖氯酸,而№.1—231从№.15—8得到。赖氨酸高产突变株№.22是从菌株№.1—231通过筛选对β—氟代丙酮酸(FP)的敏感株而得到,它 HD 缺失,此通过从№.1—231两次突变筛选高丝氨酸缺陷型的 HD 缺失突变株产生更多的赖氨酸。菌株№.22在试验的条件下,并不对FP 敏感。在测定的各种赖氨酸生物合成酶中,№.22比其亲株和后者 HD 缺失突变株具有较高活力的天冬氨酸-β-半醛脱氢酶。菌株№.22在含有大豆水解液、甲硫氨酸和100克/升葡萄糖的培养基中培养72小时,可产50克/升赖氯酸盐酸盐。     

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.     

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     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

鸡传染性法氏囊病病毒研究进展

传染性法氏囊病(Infection bursal disease, IBD)是由鸡传染性法氏囊病毒(Infectious bursal disease virus, IBDV)引起的鸡和火鸡的一种高度接触性传染病,给世界各国的禽养殖业带来了巨大损失.自IBDV发现至今新的变异株不断出现,分子结构的改变导致病毒致病力的改变及宿主对疫苗应答的改变,使得传统的疫苗已不能控制其流行,因此各国学者对其基因组结构和功能进行了广泛深入的研究,并积极研制新型有效的疫苗以达到防治的目的.     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).