微生物谷氨酰胺转胺酶生产菌株的育种研究

在简要介绍微生物谷氨酰胺转胺酶的主要功能、应用和国外研究成果与目前状况后,指出该酶生产微生物菌种选育的重要性以及实际难度和艰巨性,阐述了进行初筛、复筛和常规诱变育种试验的关键技术手段及其成果效益。利用这些有效方法获得性能优良的高产酶突变菌株,进行规模化发酵工艺条件和酶制剂产品分离提纯技术研究,并在此基础之上,进一步开展通过“神舟”四号飞船搭载的微生物空间诱变育种研究强化产酶菌株的各种优良性能,说明了空间多种复合因素引发的综合搭载效果显著。     

离子束在生物品种改良中的应用研究进展

辐射诱变育种是利用各种射线诱发生物遗传基因突变,促进基因重组和核外突变,获得有利用价值的突全体。诱变育种的辐射技术和方法在不断地发展看,辐射源由X射线、γ射线发展到快中子、电子束、空间辐射,离子束诱变育种是近十几年崛起的新技术,具有损伤轻、突变率高、突变谱广的优点,概述了这一新的品种改良技术的进展。     

“卫星灵芝”让人类更健康

1什么是太空诱变育种 自1987年以来,我国利用返回式卫星和飞船搭载了各种植物种子、微生物菌种、动物等生物材料进行太空生命科学的研究。太空诱变育种是利用返回式卫星等所能到达的空间环境对生物体诱变作用产生的变异,在地面选育新种质、新材料,培育新品种的一种新型的诱变育种方法,称为航天诱变育种或空间诱变育种也称太空诱变育种。     

植物空间诱变育种的现状与展望

本文在简要回顾植物空间诱变育种历史的基础上,论述了植物空间诱变育种的机理,植物在高真空、微重力、强辐射、交变磁场及其他因素的综合作用下产生变异和植物空间诱变育种效应以及突变性状的遗传;全面综述了空间诱变育种在中国作物新品种、特异优良种质材料的创新中取得的成就.最后对未来植物空间诱变育种的应用前景进行了展望,并指出空间诱变技术开创了植物育种的又一新途径.     

工业微生物物理诱变育种技术的新进展

物理诱变技术是当今工业微生物育种中最重要、最有效的技术之一。传统的物理诱变技术主要有紫外线、X射线、γ射线诱变等,它们已在包括青霉素、"-淀粉酶等几乎所有的工业微生物菌种的诱变选育中发挥了巨大的作用。多数菌株在多次重复使用传统诱变源时往往出现抗性饱和的现象。太空环境、离子束、激光等是20世纪70～80年代逐渐兴起的新型诱变技术,因它们具有诱变谱广和在一定程度上能克服菌株对传统诱变源的抗性饱和等优点,而广受工业微生物育种工作者的欢迎。现就空间、离子束、激光等诱变育种技术的作用特点、诱变机理、应用及前景进行阐述。     

常压室温等离子体技术在微生物诱变中的应用进展

微生物是人类赖以生存的重要资源,为提高微生物的生产效率或者赋予其新的生物学功能,需要通过理化方法进行诱变或通过分子生物学技术对其进行定点突变。在目前的理化诱变方法中,常压室温等离子（atmospheric and room temperature plasma,ARTP）诱变技术具有操作简单、条件温和、安全性高、诱变快速等优点,成为倍受青睐的新方法。基于此,综述了ARTP诱变技术的原理及其在微生物诱变育种方面的应用,以期为选育性能优越的微生物菌种的诱变育种相关研究提供借鉴。     

重离子诱变微生物育种的研究进展

近年来,重离子束作为一种新的辐射诱变源在微生物育种领域已多有应用.与传统的辐照源相比,重离子束具有更高的传能线密度,可以产生更强的辐射损伤生物效应,因此诱变效率高.本文综述了近年来重离子诱变在微生物育种中取得的进展、诱变后突变体菌株的筛选策略、重离子束引起微生物遗传物质改变的直接和间接机制以及突变后的修复机理,并对其在...     

（超）高压对微生物的影响及其诱变效应探讨

(超)高压对微生物有多方面的影响,它不仅可使微生物细胞体积形态、细胞组分发生变化,还可使微生物的基因表达和核酸结构及其生物学功能发生改变。(超)高压的这些生物学效应,使其不仅可以应用到食品杀菌、保藏及某些加工过程,而且在微生物菌种诱变方面具有很大的应用潜力。这是因为(超)高压既然可以使核酸发生变化,那么它诱导微生物发生突变就很有可能。现从(超)高压对微生物的影响出发,并结合国内外有关实例及作者的研究工作,初步探讨其诱变育种的可行性。     

药用微生物辐照诱变研究进展

常规的诱变育种方法主要是利用紫外线、激光、γ射线、中子等对微生物药物菌种进行辐照诱变,效果显著。离子束辐照微生物诱变育种在离子束生物学效应的研究中起步较晚,但其作为一种集物理诱变和化学诱变为一体的诱变育种新方法,将在辐照诱变育种中发挥重要作用。本文综述了近年来微生物药物研究与开发的动态,简要叙述微生物菌种选育的辐照诱变效应、作用机制及其在实践中的应用。     

热效应在微生物诱变育种中的应用

本文综述了微生物诱变育种中的热效应机理及其应用研究进展。热在微生物诱变育种中具有热诱变效应和热筛选效应, 热诱变效应通过热引起DNA中G-C碱基对的置换实现, 热筛选效应可以从其他诱变剂诱变的菌体中获得更高的正向突变率。     

基于功率谱分析的基因编码序列单碱基突变研究

针对DNA序列单碱基的不同类型突变,利用数字信号处理方法,研究了单碱基替换突变、删除突变、插入突变对DNA序列三周期功率谱的影响。研究结果表明:对于不同长度的编码序列,替换突变对序列功率谱的影响较小,删除突变和插入突变对序列功率谱的影响较大;随着序列编码区长度的减小,替换、删除、插入突变对序列编码区的功率谱影响会越来越大。对于中等长度外显子,插入突变对序列三周期功率谱影响最大,对于短外显子,删除突变对序列三周期功率谱的影响最大。研究结果可为含突变基因编码区的识别与检测提供参考。     

不同栖息环境的两种啮齿动物Vkorc1基因多态性

维生素K环氧化物还原酶复合物亚基1基因(Vkorc1)的变异与啮齿动物对抗凝血灭鼠剂的抗药性密切相关。为掌握Vkorc1基因变异在野栖类和家栖类啮齿动物中的流行情况,从山西省13个县(市、区)的农田和14个县(市、区)的养殖场采样,检测长尾仓鼠(Cricetulus longicaudatus)和黄胸鼠(Rattus tanezumi) Vkorc1基因编码区的变异位点及携带不同变异位点的个体的分布情况。结果显示,长尾仓鼠在13个采样地均有捕获,整体占野栖类啮齿动物的23.29%;黄胸鼠分布于8个采样地,整体占家栖类啮齿动物的68.63%。在长尾仓鼠样本(n=105)中检测到6个沉默突变位点和5个错义突变位点,其中,沉默突变C438T (His146His)的变异率最高,为67.62%;共有17只长尾仓鼠样本存在错义突变位点。黄胸鼠样本(n=70)中存在6个沉默突变位点和1个错义突变位点,其中,最常见的沉默突变位点A321C (Ile107Ile)和T411C (Thr137Thr)的变异率均达到18.57%;8只黄胸鼠样本存在与其抗药性相关的A416G (Tyr139Cys)错义突变...     

EVOLUTIONARY FEEDBACKS BETWEEN REPRODUCTIVE MODE AND MUTATION RATE EXACERBATE THE PARADOX OF SEX

Evolutionary theory suggests that low mutation rates should favor the persistence of asexuals. Additionally, given the observation that most nonneutral mutations are deleterious, asexuality may strengthen selection for reduced mutation rates. This reciprocal relationship raises the possibility of a positive feedback loop between sex and mutation rate. We explored the consequences of this evolutionary feedback with an individual‐based model in which a sexual population is continually challenged by the introduction of asexual clones. We found that asexuals were more likely to spread in a population when mutation rates were able to evolve relative to a model in which mutation rates were held constant. In fact, under evolving mutation rates, asexuals were able to spread to fixation even when sexuals faced no cost of sex whatsoever. The added success of asexuals was the result of their ability to evolve lower mutation rates and thereby slow the process of mutation accumulation that otherwise limited their spread. Given the existence of ample mutation rate variation in natural populations, our findings show that the evolutionary feedback between sex and mutation rate may intensify the “paradox of sex,” supporting the argument that deleterious mutation accumulation alone is likely insufficient to overcome the reproductive advantage of asexual competitors in the short term.     

Minisatellite germline mutation rate in the Techa River population

Germline mutation at eight minisatellite loci has been studied among the irradiated families from the Techa River population and non-exposed families from the rural area of the Chelyabinsk and Kurgan Oblasts. The groups were matched by ethnicity, parental age, occupation and smoking habit. A statistically significant 1.7-fold increase in mutation rate was found in the germline of irradiated fathers, whereas maternal germline mutation rate in the exposed families was not elevated. Most of the minisatellite loci showed an elevated paternal mutation rate in the exposed group, indicating a generalised increase in minisatellite germline mutation rate in the Techa River population. These data suggest that the elevated minisatellite mutation rate can be attributed to radioactive exposure. The spectra of paternal mutation seen in the unexposed and exposed families were indistinguishable.     

肺炎链球菌pbp2b和pbp1a基因突变与青霉素耐药的相关性研究

目的探讨耐青霉素肺炎链球菌pbp2b和pbp1 a基因的突变与青霉素耐药的关系,为明了肺炎链球菌的耐药性变异机制,防治其感染提供实验依据。方法从呼吸道感染患儿痰标本中分离肺炎链球菌163株,液体培养基连续稀释法测定其对青霉素的最小抑菌浓度(M IC),套式聚合酶链反应(nPCR)扩增pbp2b和pbp1 a基因,扩增产物直接DNA测序,所测序列与青霉素敏感株(SPN R6)的基因序列进行比较,并分析其氨基酸结构的改变。结果 163株肺炎链球菌中检出青霉素敏感菌75株,中度敏感17株,青霉素耐药菌71株(44%)。耐药菌中58株存在pbp2b突变(81.7%),其中,56株为点突变,2株为CCT插入突变;在27株有pbp2b基因突变的B型和C型耐药菌中,21株出现了不同程度的pbp1 a基因突变。PBP2B氨基酸结构改变以苏氨酸变为丙氨酸、精氨酸变为赖氨酸为主,PBP1A以丙氨酸变为苏氨酸、谷氨酸变为天门冬氨酸为主。结论肺炎链球菌的pbp2b和pbp1 a基因突变与对青霉素的耐药性密切相关,PBP2b突变导致低水平耐药;PBP2b和PBP1A突变导致高水平耐药。     

A frequent tyrosinase gene mutation associated with type I-A (tyrosinase-negative) oculocutaneous albinism in Puerto Rico.

We have determined the mutations in the tyrosinase gene from 12 unrelated Puerto Rican individuals who have type I-A (tyrosinase-negative) oculocutaneous albinism (OCA). All but one individual are of Hispanic descent. Nine individuals were homozygous for a missense mutation (G47D) in exon I at codon 47. Two individuals were heterozygous for the G47D mutation, with one having a missense mutation at codon 373 (T373K) in the homologous allele and the other having an undetermined mutation in the homologous allele. One individual with negroid features was homozygous for a nonsense mutation (W236X). The population migration between Puerto Rico and the Canary Islands is well recognized. Analysis of three individuals with OCA from the Canary Islands showed that one was a compound heterozygote for the G47D mutation and for a novel missense mutation (L216M), one was homozygous for a missense mutation (P81L), and one was heterozygous for the missense mutation P81L. The G47D and P81L missense mutations have been previously described in extended families in the United States. Haplotypes were determined using four polymorphisms linked to the tyrosinase locus. Haplotype analysis showed that the G47D mutation occurred on a single haplotype, consistent with a common founder for all individuals having this mutation. Two different haplotypes were found associated with the P81L mutation, suggesting that this may be either a recurring mutation for the tyrosinase gene or a recombination between haplotypes.     

一个46,XY"女性"不育症家系的遗传学分析

运用常规的染色体G带分析和基因分析技术对-46,XY男性女性化家系进行遗传学分析,发现：先证者及其妹妹的染色体核型为46,XY,其母亲和父亲的核型正常;对睾丸决定基因（SRY）和雄激素受体基因（AR）进行突变检测,在SRY基因的整个编码区中没有发现突变,而AR基因的第7个外显子的第840个密码子由CGT（编码精氨酸）变为CAT（编码组氨酸）,这一改变可能是导致核型为46,XY女性化而发生不育。     

Studies on the cross-resistance of Mycobacterium tuberculosis, strain H37Rv, to aminoglycoside- and peptide-antibiotics

Various phenotypes of the resistance to aminoglycoside- and peptide-antibodies of Mycobacterium tuberculosis strain H37Rv were produced by single- and/or two-step selection of the parent strain. Mutants obtained by single-step selection with antibiotics were classified into ten phenotypes; one of single resistance, two of triple resistance, three of quadruple resistance, and four of sextuple resistance. There were two kinds of sextuple resistance (high resistance to enviomycin, viomycin, capreomycin, kanamycin, lividomycin). One was isolated from the parent strain by single-step selection and could be eliminated by mutation to isoniazid resistance, the other was obtained by two-step selections and was not eliminated by mutation to isoniazid resistance. Interaction between mutation to streptomycin resistance and mutation to quadruple resistance (4R phenotype) was observed. Streptomycin resistance interfered with the formation of the 4R phenotype and produced a different phenotype, KR instead of the 4R phenotype. The existence of mutation of the 4R phenotype did not usually interfere with mutation to streptomycin resistance, but a small portion of the mutants with the 4R phenotype were altered in their phenotype from 4R to KR after addition of the mutation to streptomycin resistance. This effect of the mutation to streptomycin resistance was not observed in mutants which already had a mutation to klR phenotype (mutation to low concentrations of kanamycin only).     

Beta-thalassemia mutations in Indonesia and their linkage to beta haplotypes.

A total of 72 chromosomes from 36 Indonesian patients, 23 with beta-thalassemia major and 13 with Hb E-beta-thalassemia, were analyzed by specific oligonucleotide hybridization after DNA amplification. Thirteen had the beta E mutation (codon 26 GAG----AAG). Of the 59-beta-thalassemic chromosomes, 32 were of the variant IVS-1 nt5 (G----C). Seven had the mutation IVS-2 nt654 (C----T), one had the mutation codon 41/42 (deletion CTTT), and one had the mutation codon 17 (AAG----TAG). Another six with the mutation IVS-1 nt1 (G----T), one with the mutation IVS-1 nt1 (G----A), four with the mutation codon 15 (TGG----TAG), one with a mutation codon 30 (AGG----ACG), and one with a mutation codon 35 (deletion C) were first identified by direct sequencing of a patient's genomic DNA followed by further hybridizing other patients' DNA with the appropriate oligonucleotide probes. Five did not carry the common mutations previously described in Asian populations. The four most prevalent mutations encountered made up 83% of the total number of beta-thalassemic chromosomes studied. The most common mutation, IVS-1 nt5 (G----C), was mostly associated with two different haplotypes.     

Clinical characteristics of patients with unicoronal synostosis and mutations of fibroblast growth factor receptor 3: a preliminary report.

Clinical teaching dictates that isolated unicoronal synostosis is sporadic in occurrence and is possibly related to intrauterine constraint. Despite this, isolated reports document a familial occurrence. It has previously been recognized that there may be a familial pattern of inheritance. Recently, mutations in fibroblast growth factor receptors (FGFRs) have been implicated in several syndromic craniosynostoses. At the authors' institution, mutations in FGFR3, located at chromosome 4p16, have been found to cause coronal synostosis. Two cases of unicoronal synostosis were found to have the same Pro250Arg missense mutation in FGFR3. This finding suggested that all patients with a diagnosis of unicoronal synostosis be screened for the FGFR3 mutation. Between January and December of 1996, patients with a diagnosis of plagiocephaly at the Children's Hospital of Philadelphia were evaluated for the FGFR3 mutation. Thirty-seven patients with unicoronal synostosis had mutational studies. Two additional patients were known to have the FGFR3 mutation at the onset of the study. Of the 37 patients screened, four were found to have the FGFR3 mutation, for a total of six patients with both unicoronal synostosis and the FGFR3 mutation. All patients with unicoronal synostosis were evaluated for facial dysmorphology and operative outcome. The six patients with the FGFR3 mutation had more severe cranial dysmorphology and were more likely to need surgical revision than those without the FGFR3 mutation. The occurrence of the FGFR3 mutation among patients with unicoronal synostosis provides evidence for a genetic basis of certain forms of plagiocephaly. The clinical, radiologic, and molecular findings will be an important addition to the surgical management and counseling of patients with unicoronal synostosis.