超高压在工业微生物诱变选育中的应用初探

超高压对微生物有多方面的影响,它不仅可使微生物细胞组分、体积形态发生变化,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。     

肉类工业微生物诱变及应用研究进展

随着分子生物学、细胞生物学及分子遗传学等学科的迅猛发展,对微生物诱变分子机理的研究也日益完善。从微生物诱变分子机理出发,着重介绍了DNA损伤分子机理、基因突变分子机理和诱变剂的种类及遗传效应,同时,列举了诱变菌在肉类工业中的应用。     

离子注入微生物诱变育种的研究与应用进展

离子束作为一种新的诱变源虽然在微生物上的应用起步较晚,但成果显著。这项技术适用于多种微生物,也可以和其它方法结合对菌种进行复合诱变,同样离子束介导转基因技术不仅适于植物细胞,对微生物细胞也是可行的。这一技术在对微生物诱变育种的研究中,表现出比传统诱变方法高的诱变效率,利用离子注入进行微生物菌种改良已在生产实践中得到广泛的应用,并取得了显著的经济效益和社会效益。对离子注入微生物诱变育种的理论研究进展和实际应用情况进行了综述。     

生物安全柜与超净工作台的设计要求、验证及应用

随着生物技术发展突飞猛进 ,由此也产生了生物学危险。这是指由于生物学上的原因而造成危害 ,即在处理细菌、病毒等微生物或核酸、蛋白质等微生物构成成分或微生物所生产的产物这三种情况下所发生的危险或灾害。有关实验室感染加深了人们对生物学危险的认识。空气洁净技术的发展与应用使人们认识到隔离是防止危险性微生物向外界扩散的基本原理。本文介绍的生物学安全柜 (生物安全柜 )便是有效的方法。超净工作台则应用于非危险性微生物的操作 ,它虽对操作者没有保护作用 ,但所形成的局部净化环境可避免操作过程污染杂菌的可能。本文从生物安…     

FT-IR光谱在电离辐射作用于微生物研究中的应用

傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FT-IR)是一种很有用的生物分析检测技术,通过FT-IR光谱技术可以得到有关蛋白质、脂类、核酸和多糖等微生物和细胞各类组成成分的信息。基于同步辐射光源的显微FT-IR光谱具有更高的空间分辨率和更快的测量速度,因而在生物学研究中具有进行快速、实时、动态和无损检测等优势。本文介绍了FT-IR光谱技术在微生物及电离辐射作用于微生物引起的生物学效应研究中的应用,并对该领域未来研究的发展趋势进行了展望。     

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。     

原子力显微镜在生物学研究中的应用进展

原子力显微镜（atomic force microscope,AFM)具有原子级分辨率,能够在生理条件下对生物样品进行观察,本综述了AFM的原理及技术要点,举例说明了它在核酸,蛋白质,微生物及细胞等领域的应用进展,相信AFM必将在生物学研究中起到越来越重要的作用。     

抗生素对微生物作用的研究

抗生素能干扰微生物细胞新陈代谢的某个或几个环节 (包括代谢物或酶系统 ) ,使它不能以正常的代谢途径维持和延续生命活动。分别从抗生素抑制细胞壁合成、影响细胞膜功能、抑制蛋白质合成、影响能量代谢、干扰核酸合成 5方面综述了抗生素对微生物的作用。     

低能氮离子注入大肠杆菌诱发的生物学效应研究

研究离子注入的诱变和导入外源DNA的生物学效应,用低能氮离子注入处理大肠杆菌野生型菌株MC4100A,将含水母绿色荧光蛋白基因的质粒导入细胞中。实验结果表明,在一些转化子中绿色荧光蛋白的表达或折叠受到了影响,一些转化子丧失了分裂后分离能力,且细胞膜有一定程度的损伤,为进一步研究微生物细胞分裂和蛋白质折叠机理提供了菌株。故低能氮离子注入对微生物细胞的诱变效应和导入外源DNA效应的有机结合将使离子注入技术在生物学基础研究中有着广泛的应用前景。     

微生物胶原酶

某些微生物可以分泌微生物胶原酶。微生物胶原酶具有和脊椎动物胶原酶相似的生物学作用 ,可以降解细胞外基质的主要成分—胶原 ,其活性依赖于Ca2 + 等二价金属阳离子。但微生物胶原酶又具有许多不同于脊椎动物胶原酶的生物学特性。它不仅可以降解天然不溶性胶原纤维 ,也可以降解变性的可溶性胶原蛋白、人工合成的胶原酶底物以及其它细胞外基质糖蛋白。越来越多的研究表明 ,微生物胶原酶在一些微生物致病过程中起重要作用 ,是某些微生物的重要毒力因子。而且微生物胶原酶也被越来越广泛地应用于生命科学基础研究和临床某些疾病治疗 ,具有极为广阔的应用前景。     

Somatic mutations in organisms with complex life histories.

A theoretical model is developed of the fate of mutations for organisms with such life-history characteristics as indeterminate growth and clonal reproduction. It focuses on how the fate of a particular mutant depends on whether it arises during mitotic cell division (somatic mutation) or during meiotic cell division (meiotic mutation). At gamete production, individuals carrying somatic mutations will produce some proportion of gametes reflecting the original, zygotic genotype and some proportion reflecting genotypes carrying the somatic mutation. Focusing on allele frequencies at gamete production allows the effects of growth and clonal reproduction to be summarized. The relative strengths of somatic and meiotic mutation can be determined, as well as the conditions under which the change in allele frequency due to one is greater than that due to the other. Examples from a published demographic study of clonal corals are used to compare somatic and meiotic mutation. When there is no selection acting on either type of mutation, only a few cell divisions per time unit on average are needed for the change in allele frequency due to somatic mutation to be greater, given empirically based mutation rates. When somatic selection is added, the most dramatic effect is seen with fairly strong negative selection acting against the somatic mutation within individuals. In this case, selection within organisms can effectively counteract the effects of somatic mutation, and the change in allele frequency due to somatic mutations will not be greater than that due to meiotic mutations for reasonable numbers of within-generation cell divisions. The majority of the mutation load, which would have been due to somatic mutation, is purged by selection within the individual organism.     

土壤微生物对气候变暖和大气N沉降的响应

气候变暖和大气N沉降是近一、二十年来人们非常关注的全球变化现象,它们所带来的一系列生态问题已成为全球变化研究的重要议题。它们不仅影响地上植被生长和群落组成,还直接或间接地影响土壤微生物过程,而土壤微生物对此做出的响应正是生态系统反馈过程中非常重要的环节。该文分别从气候变化对土壤微生物的影响(土壤微生物量、微生物活动和微生物群落结构)和土壤微生物对气候变化的响应(凋落物分解、养分利用与循环以及养分的固持与流失)两个角度,综述近期土壤微生物对气候变暖和大气N沉降响应与适应的研究进展。气候变暖和大气N沉降对土壤微生物的影响更多地反映在微生物群落的结构和功能上,而土壤微生物量、微生物活动和群落结构的变化又会通过改变凋落物分解、养分利用和C、N循环等重要的土壤生态系统功能和过程做出响应,形成正向或负向反馈,加强或削弱气候变化给整个陆地生态系统带来的影响。然而,到目前为止土壤微生物的响应对陆地生态系统产生的最终结果仍是未决的关键性问题。     

干旱半干旱区氮沉降生态效应研究进展

随着人类活动干扰的加剧以及全球气候变化,大气氮沉降的生态效应日益成为人们关注的焦点.氮沉降的增加能够带来生态系统结构和功能的改变,引起一系列生态效应.氮沉降对干旱半干旱地区生态系统的影响主要包括以下方面:(1)在干旱半干旱地区,氮沉降主要以脉冲形式进入氮循环进而影响其它生态过程;(2)氮沉降能够增加土壤氮矿化和土壤无机氮浓度,但氮循环还会受许多其它因素的影响;(3)氮沉降对土壤微生物代谢活动有很强的促进作用,但对其生物量的影响存在争议;(4)氮沉降能够影响植物生产力、根的生长,其效应主要受到水的调节作用;(5)氮沉降能够降低本地种的物种丰富度,有利于外来1年生物种的入侵.     

Cardiac-specific attenuation of natriuretic peptide A receptor activity accentuates adverse cardiac remodeling and mortality in response to pressure overload

Atrial (ANP) and brain (BNP) natriuretic peptides are hormones of myocardial cell origin. These hormones bind to the natriuretic peptide A receptor (NPRA) throughout the body, stimulating cGMP production and playing a key role in blood pressure control. Because NPRA receptors are present on cardiomyocytes, we hypothesized that natriuretic peptides may have direct autocrine or paracrine effects on cardiomyocytes or adjacent cardiac cells. Because both natriuretic peptides and NPRA gene expression are upregulated in states of pressure overload, we speculated that the effects of the natriuretic peptides on cardiac structure and function would be most apparent after pressure overload. To attenuate cardiomyocyte NPRA activity, transgenic mice with cardiac specific expression of a dominant-negative (DN-NPRA) mutation (HCAT D 893A) in the NPRA receptor were created. Cardiac structure and function were assessed (avertin anesthesia) in the absence and presence of pressure overload produced by suprarenal aortic banding. In the absence of pressure overload, basal and BNP-stimulated guanylyl cyclase activity assessed in cardiac membrane fractions was reduced. However, systolic blood pressure, myocardial cGMP, log plasma ANP levels, and ventricular structure and function were similar in wild-type (WT-NPRA) and DN-NPRA mice. In the presence of pressure overload, myocardial cGMP levels were reduced, and ventricular hypertrophy, fibrosis, filling pressures, and mortality were increased in DN-NPRA compared with WT-NPRA mice. In addition to their hormonal effects, endogenous natriuretic peptides exert physiologically relevant autocrine and paracrine effects via cardiomyocyte NPRA receptors to modulate cardiac hypertrophy and fibrosis in response to pressure overload.     

Glycine Insertion Makes Yellow Fluorescent Protein Sensitive to Hydrostatic Pressure

Fluorescent protein-based indicators for intracellular environment conditions such as pH and ion concentrations are commonly used to study the status and dynamics of living cells. Despite being an important factor in many biological processes, the development of an indicator for the physicochemical state of water, such as pressure, viscosity and temperature, however, has been neglected. We here found a novel mutation that dramatically enhances the pressure dependency of the yellow fluorescent protein (YFP) by inserting several glycines into it. The crystal structure of the mutant showed that the tyrosine near the chromophore flipped toward the outside of the β-can structure, resulting in the entry of a few water molecules near the chromophore. In response to changes in hydrostatic pressure, a spectrum shift and an intensity change of the fluorescence were observed. By measuring the fluorescence of the YFP mutant, we succeeded in measuring the intracellular pressure change in living cell. This study shows a new strategy of design to engineer fluorescent protein indicators to sense hydrostatic pressure.     

Salt stress impact on the molecular structure and function of the photosynthetic apparatus--the protective role of polyamines

In the present study the green alga Scenedesmus obliquus was used to assess the effects of high salinity (high NaCl-concentration) on the structure and function of the photosynthetic apparatus and the possibility for alleviation by exogenous putrescine (Put). Chlorophyll fluorescence data revealed the range of the changes induced in the photosynthetic apparatus by different NaCl concentrations, which altogether pointed towards an increased excitation pressure. At the same time, changes in the levels of endogenous polyamine concentrations, both in cell and in isolated thylakoid preparations were also evidenced. Certain polyamine changes (Put reduction) were correlated with changes in the structure and function of the photosynthetic apparatus, such as the increase in the functional size of the antenna and the reduction in the density of active photosystem II reaction centers. Thus, exogenously added Put was used to compensate for this stress condition and to adjust the above mentioned changes, so that to confer some kind of tolerance to the photosynthetic apparatus against enhanced NaCl-salinity and permit cell growth even in NaCl concentrations that under natural conditions would be toxic.     

川南天然常绿阔叶林人工更新后土壤团粒结构的分形特征

运用分形模型研究了川南天然常绿阔叶林及其人工更新成檫木(Sassafras tzumu)林、柳杉(Cryptomeria fortunei)林和水杉(Metasequoia glyptostroboides)林后土壤团粒结构,探讨了分形维数与林地土壤水源涵养功能、肥力特征和微生物数量之间的关系。结果表明:天然常绿阔叶林人工更新后土壤团粒结构的分形维数和结构体破坏率增大、土壤物理性质变差、养分含量和微生物数量降低,3种人工林中,檫木林较好、水杉林次之、柳杉林最差;土壤团聚体、水稳性团聚体和水稳性大团聚体含量越高分形维数越小;在湿筛条件下,土壤结构体破坏率随分形维数的降低而减小;土壤团粒结构的分形维数与土壤物理性质、养分含量和微生物数量之间存在显著的回归关系。这表明天然常绿阔叶林人工更新后由于不同林分对林地土壤组成结构的维护效果不同,导致更新后林地土壤物理、化学和生物性质变化,林地土壤团粒结构的变化,进而影响其分形维数的大小。因此,分形维数可作为天然常绿阔叶林及其人工更新后林地土壤水源涵养功能、肥力特征和微生物活动情况的一项综合性定量化评价指标。同时,为保护天然常绿阔叶林、选择适宜的更新树种和天然常绿阔叶林人工更新后林地土壤的科学管理提供依据,也为退耕还林中树种的选择提供参考。     

Ultrastructure of rigid and lignified forage tissue degradation by a filamentous rumen microorganism.

A small (less than 1 mum)-filamentous, branching microorganism was observed in Gram-stained smears of the rumen microflora and was found to degrade tissues in forage samples incubated in vitro and in vivo with rumen fluid and observed by scanning and transmission electron microscopy. The microbe had prokaryotic cytoplasmic features and a gram-positive type of cell wall structure. Round to oval bodies apparently attached to hyphae resembled the sporulation pattern reported for Micromonospora. Filaments and rod and coccal forms of the microbe degraded rigid forage cell walls and lignified, thick-walled sclerenchymal cells. Location of the microbe at a slight distance from the degraded zones suggested the action of extracellular enzymes. The presence of a microbe with the capability of degrading lignified tissue represents an important and unique function in the rumen ecosystem.     

The ovotestis: an underdeveloped organ of evolution

In animals that have separate sexes (gonochorists), many sperm are produced to fertilise a few eggs. As the male germline undergoes more mitoses, so the accumulated mutation frequency is elevated in sperm compared with ova, and evolution is 'male-driven'. In contrast, in many hermaphroditic animals, a single organ--the ovotestis--produces both ova and sperm. Since self-renewing cells in the ovotestis may give rise to both cell types throughout life, ova in hermaphrodites could in theory have undergone as many cell divisions as sperm. Here, I consider some possible effects of the ovotestis on evolution. In particular, I hypothesise that the accumulated mutation frequency of nuclear genes in hermaphrodites (including species that change sex) may reach twice that compared with gonochorists. There may be an even greater increase in the mitochondrial mutation frequency. Further developmental studies and the accumulation of comparative data should allow hypothesis testing. If the prediction is correct, then it may provide the most-straightforward explanation for the extraordinary diversity of mitochondrial DNA in some hermaphrodites, especially molluscs.