极端嗜盐菌的特性及其应用前景

主要介绍极端嗜盐菌的嗜盐机理、细菌视紫红质(bR)和嗜盐菌素的研究进展,然后对其在环境生物治理、生物电子和医药工业等领域的应用研究进行总结和展望。     

光遗传技术中的两种主要光敏蛋白及其在阿尔茨海默病研究中的应用

阿尔茨海默病(Alzheimer’s disease, AD)是一种常见的中枢神经系统退行性疾病,但是,AD的发病机制还有待进一步的阐明。近年来,光遗传技术因其在时间和空间上的高精确性而逐渐被应用于AD的研究中。Ⅰ型光敏蛋白中的视紫红质通道蛋白-2 (channelrhodopsin-2, ChR2)和盐碱古菌嗜盐细菌视紫红质蛋白(Natronomonas halorhodopsin, NpHR)可以通过将光信号快速转换成跨膜离子电流来调节神经元的活动,因此,已经被应用于光遗传技术中。现对ChR2和NpHR在光遗传技术中的应用进行介绍,并总结其在AD研究中的应用进展。     

温度和pH对嗜盐菌紫膜吸收和圆二色谱的作用

嗜盐菌紫膜可见光区域的圓二色谱由二部分重迭组成,一部分是较宽的正带,它来自细菌视紫红质分子内视黄醛和菌蛋白之间相互作用,另一部分是由对称的正带、负带组成的激子带,它来自膜内相邻细菌视紫红质分子生色团的相互作用。因此,紫膜的圓二色谱可反映膜上蛋白的晶体结构和构象变化,被认为是研究嗜盐菌紫膜结构变化的一种天然探针。本文用圆二色谱和吸收谱观察了温度和pH对光适应紫膜结构的影响。     

细菌视紫红质的基因克隆与表达

细菌视紫红质的基因克隆与表达卢春林,汪俭,梅祺,韦钰（东南大学吴建雄实验室,南京２１０Ｏ１８）叶寅,田波（中国科学院微生物研究所,北京１０００８０）关键词细菌视紫红质基因;聚合酶链反应（ＰＣＲ）;基因克隆与表达细菌视紫红质（ｂａｅ快ｒｉｏｒｈｏｄｏＰ...     

美国《Bioscience》出版“质子泵”专集

美国《Bioscience》35卷1期(1985)出版“质子泵”专集,发表C.L.Slayman等人撰写的有关质子泵的化学、分子结构、功能和进化等方面的文章7篇。该专集总结了生物与生物膜中存在5种类型的质子泵(H~+-ATP酶),并对它们分别作了介绍:(Ⅰ)存在于嗜盐细菌被膜中的视紫红质,是一种光致质子泵;     

微生物与燃料电池的开发

开发“活体电池”苏格兰格拉斯哥大学研究人员从干塘底部样品中获得一种行光合作用的细菌（有特殊的细胞结构、超常地保存光能）,能迅速地（只需有万分之一秒）将光能转化为电能而储存起来。应该说,这是一种“高能蓄能的活体”,它作为一种“活体蓄电池”具有将光能转化为电能的本领,其有效率可达９５％（人造太阳能电池的有效率仅为２０％）。开发嗜盐菌电池美国研究人员从死海或大盐湖中找到一种嗜盐菌,并从中获取视紫红质,称之为细菌视紫红质（ｂａｃｔｅｒｉｏｒｈｏｄｏｐｓｉｎ）,该菌能接受约１０％的阳光转化为化学能时即可产…     

嗜盐古生菌AJ4中BR蛋白基因部分片段和16S rRNA基因序列研究

为了研究分析新疆阿尔金山国家自然保护区阿牙克库木湖嗜盐古生菌物种与细菌视紫红质(bacteriorhodopsin ,BR)蛋白资源 ,对分离纯化到的极端嗜盐古生菌AJ4 ,采用PCR方法扩增出其 16SrRNA基因 (16SrDNA)和编码螺旋C至螺旋G的BR蛋白基因片断 ,并测定了基因的核苷酸序列 .通过BR蛋白部分片段序列分析表明 ,BR蛋白中对于完成质子泵功能以及与视黄醛结合的关键性氨基酸残基均为保守序列 ,位于膜内侧的序列比位于膜外侧的序列更保守 ;基于BR蛋白基因和16SrDNA序列的同源性比较以及 16SrDNA序列的系统发育学研究表明 ,AJ4是Haloarcula属中新成员 .由此建立了一种快速筛选具有新BR蛋白的新嗜盐古生菌的方法 .     

细菌视紫红质对调制光的响应特性

细菌视紫红质在结构上与视紫红质的相似性使其具有某些视觉响应特性.用电泳法在不锈钢电极上沉积出定向紫膜薄膜,构成不锈钢/紫膜/凝胶/铜电极结构的光接收器.在调制光作用下,光接收器显示出对光强变化的微分响应特性.测量了光电压随调制频率和入射光功率的变化关系.比较和讨论了细菌视紫红质对调制光响应特性与视觉频闪及明暗感的相关性.     

基因突变细菌视紫红质薄膜的长寿命M态光存储

实验研究了D96N型基因突变细菌视紫红质薄膜的光存储性能,实现了用670 nm激光在BR膜上记录光学图像,用560 nm弱光读出图像,用488 nm激光擦除图像的写读擦操作.M态寿命在室温下延长到了3 min,比溶液状态下的野生细菌视紫红质M态寿命延长了5个数量级.     

微小杆菌属(Exiguobacterium)细菌的能量代谢途径分析

【目的】微小杆菌属(Exiguobacterium)细菌广泛分布于海洋及非海洋环境中,具有多种代谢途径以适应复杂多样的生境。本研究从能量代谢途径角度出发,探究该属菌株对不同生境的适应能力。【方法】从美国国家生物科技数据中心(National Center for Biotechnology Information, NCBI)数据库中获取146个Exiguobacterium属菌株的基因组,查找并统计光营养、厌氧呼吸和底物代谢等多种能量代谢途径的关键蛋白或关键酶基因在各菌株基因组中的分布,包括光营养型的视紫红质基因、厌氧呼吸营养型的钼辅因子合成蛋白基因,以及底物代谢营养型中乙醛酸分流途径的异柠檬酸裂解酶及苹果酸合酶基因等。根据对应的氨基酸序列构建视紫红质、MoaC和异柠檬酸裂解酶的系统发育树,分析不同能量代谢途径在该属菌株进化过程中的保守性,推测其对于该属菌株的重要性。【结果】Exiguobacterium属中50%的种具有视紫红质基因,其中分离自非海洋生境的菌株更趋向于含有视紫红质基因。本研究所统计的全部非海洋生境菌株中,含有视紫红质基因的菌株占比约为70%,而在海洋生境菌株中该比例...     

The use of photothermal radiometry in assessing leaf photosynthesis: I. General properties and correlation of energy storage to P700 redox state

Energy storage measurements by modulated photothermal radiometry (PTR) were carried out on intact leaves to assess the value of the PTR method for photosynthesis research. In particular, correlations to the redox state of P₇₀₀ under various conditions were examined. PTR monitors modulated light conversion to heat by sensing the resulting modulated infra-red radiation emitted from the leaf. It is, therefore, a complementary method to photoacoustics for estimating energy storage and its time variation, particularly under controlled leaf atmosphere.With modulated light-1 (>690 nm) the energy storage approached zero and P₇₀₀ was maximally oxidized. When background light of shorter wavelength (<690 nm-light-2) was added, energy storage momentarily increased (a manifestation of Emerson enhancement) while P₇₀₀ was reduced. The values of both parameters varied as a function of the background light intensity, keeping a mutual linear relationship. Following the initial change, there was a slow reversal transient of P₇₀₀ oxidation with a parallel decrease in energy storage. Temporal correlation to P₇₀₀ redox state after dark adaptation was observed also for the energy storage measured in modulated light 2 when combined with background actinic light of medium intensity (about 50 W m²). Under these circumstances P₇₀₀ was almost totally oxidized initially and then gradually reduced while energy storage was initially low and then increased parallel to P₇₀₀ reduction.A comparison between the maximum energy storage in modulated light 1, enhanced by background light 2, to the energy storage with short wavelength light (where light tends to be more evenly distributed) indicates a comparable contribution to energy storage from each active photosystem. The above experiments indicate that energy storage contribution from PS I is directly related to the extent of openness of its reaction-centers.While some aspects of the data call for more experimentation, these experiments already establish PTR as a valuable method to monitor photosynthetic energy storage activity in vivo, particularly when used simultaneously with other non-invasive methods.Abbreviations ES energy storage - light 1 or light 2 light of spectral distribution which favors absorption in PS I or PS II, resp. - PTR photothermal radiometry - P₇₀₀ the primary donor in PS I reaction center     

Characterization of energy conversion based on metabolic flux analysis in mixotrophic liverwort cells, Marchantia polymorpha

In order to characterize the contributions of respiratory and photosynthetic actions to energy conversions, the mixotrophic cells of Marchantia polymorpha were cultivated in the medium containing 10kg/m(3) glucose as an organic carbon source. The cultures were conducted with the supply of ordinary air (0.03% CO(2)) at constant incident light intensities of 50 and 180W/m(2). From the results of metabolic analysis, it was found that the cell yield based on ATP synthesis was estimated to be 6.3x10(-3)kg-dry cells/mol-ATP in these cultures. Under the examined conditions, energy conversion efficiency through respiration was larger than that through photosynthesis, and efficiency of overall energy conversion to ATP was maximized when the sum of energies from glucose and light captured by the cells was approximately 7.2x10(5)J/(hkg-dry cells). Taking into account the efficiency of overall energy conversion, a batch culture of M. polymorpha in a bioreactor was carried out by regulating incident light intensity ranging from 9 to 58W/m(2). In the culture with light regulation, the cell yield of 6.2x10(-9)kg-dry cells/J was achieved on the basis of energy provided to the system throughout the culture, and this value was 2.3 and 9.3 times as large as those obtained in the cultures under constant incident light intensities of 50 and 180W/m(2), respectively.     

Monoenergetic proton beams from mass-limited targets irradiated by ultrashort laser pulses

Results are presented from three-dimensional numerical simulations carried out to study different regimes of proton acceleration from plane targets (such as double- and single-layer foils, homogeneous foils of light and heavy ions, and mass-limited targets) irradiated by laser pulses of moderate intensity. It is shown that, in the interaction of a laser pulse having an energy of about 20 J with mass-limited targets consisting of heavy ions and protons, it is possible to generate a monoenergetic proton beam with an energy of about 150 MeV.     

ApcD is necessary for efficient energy transfer from phycobilisomes to photosystem I and helps to prevent photoinhibition in the cyanobacterium Synechococcus sp. PCC 7002

Phycobilisomes (PBS) are the major light-harvesting, protein-pigment complexes in cyanobacteria and red algae. PBS absorb and transfer light energy to photosystem (PS) II as well as PS I, and the distribution of light energy from PBS to the two photosystems is regulated by light conditions through a mechanism known as state transitions. In this study the quantum efficiency of excitation energy transfer from PBS to PS I in the cyanobacterium Synechococcus sp. PCC 7002 was determined, and the results showed that energy transfer from PBS to PS I is extremely efficient. The results further demonstrated that energy transfer from PBS to PS I occurred directly and that efficient energy transfer was dependent upon the allophycocyanin-B alpha subunit, ApcD. In the absence of ApcD, cells were unable to perform state transitions and were trapped in state 1. Action spectra showed that light energy transfer from PBS to PS I was severely impaired in the absence of ApcD. An apcD mutant grew more slowly than the wild type in light preferentially absorbed by phycobiliproteins and was more sensitive to high light intensity. On the other hand, a mutant lacking ApcF, which is required for efficient energy transfer from PBS to PS II, showed greater resistance to high light treatment. Therefore, state transitions in cyanobacteria have two roles: (1) they regulate light energy distribution between the two photosystems; and (2) they help to protect cells from the effects of light energy excess at high light intensities.     

Flux balance analysis of Chlorella sp. FC2 IITG under photoautotrophic and heterotrophic growth conditions

Quantification of carbon flux distribution in the metabolic network of microalgae remains important to understand the complex interplay between energy metabolism, carbon fixation, and assimilation pathways. This is even more relevant with respect to cyclic metabolism of microalgae under light–dark cycle. In the present study, flux balance analysis (FBA) was carried out for an indigenous isolate Chlorella sp. FC2 IITG under photoautotrophic and heterotrophic growth conditions. A shift in intracellular flux distribution was predicted during transition from nutrient sufficient phase to nutrient starvation phase of growth. Further, dynamic flux analysis (dFBA) was carried out to capture light–dark metabolism over discretized pseudo steady state time intervals. Our key findings include the following: (i) unlike heterotrophic condition, oxidative pentose phosphate (PP) pathway, and Krebs cycle were relatively inactive under photoautotrophic growth; (ii) in both growth conditions, while transhydrogenation reaction was highly active, glyoxalate shunt was found to be nonoperative; (iii) flux distribution during transition period was marked with up regulation of carbon flux toward nongrowth associated (NGA) maintenance energy, oxidative phosphorylation, and photophosphorylation; (iv) redirection of carbon flux from polysaccharide and neutral lipid resulted in up regulation of Krebs cycle flux in the dark phase; (v) elevated glycolytic and acetyl-CoA flux were coupled with induction of neutral lipid during light cycle of the growth; (vi) significantly active photophosphorylation in the light phase was able to satisfy cellular energy requirement without need of oxidative PP pathway; and (vi) unlike static FBA, dFBA predicted an unaltered NGA maintenance energy of 1.5 mmol g^?1 DCW h^?1.     

Effects of Different Spectra from LED on the Growth,Development and Reproduction of <i>Arabidopsis thaliana</i>

Light is the major source of energy for plants and as such has a profound effect on plant growth and development. Red and blue lights have been considered to best drive photosynthetic metabolism and are beneficial for plant growth and development, and green light was seen as a signal to slow down or stop. In this study, Arabidopsis thaliana (Arabidopsis) was used to investigate the effects of red, blue and green lights on the growth and development of plants from seed germination to seeding. Results demonstrated that red light showed a promotion effect but blue light a prohibition one in most stages except for the flowering time in which the effect of each light was just reversed. When mixed with red or blue light, green light generally at least partially cancelled out the effects caused by each of them. Results also showed that the same number of photons the plant received could cause different effects and choosing the right combination of different color of lights is essential in both promoting the growth and development of plants and reducing the energy consumption of lighting in plant factory.     

Kinetic analysis of the growth of Chlorella vulgaris

The energy of the total transmitted light was subtracted from that of the incident light in a culture vessel and the difference was divided by the weight of cells. The value thus obtained was defined as the amount, E(x), of light energy absorbed per unit cell weight per unit time.Batch and continuous cultures of Chlorella vulgaris were carried out at 30 degrees C in the pH range of 6.4-6.7 while restricting illumination. Next the specific growth rate, mu, in the batch culture and the fixed dilution rate, D, in the continuous culture were plotted against E(x). The results showed that the relation between D and E(x) can be expressed in a Michaelis-Menten equation, where the maximal specific growth rate is 0.24 h (-1) and the saturation constant is 6.58 kcal/g . h.Cell concentration calculated by substituting the apparent concentration, X(e), of incubated cells and the apparent maintenance constant, M(e), for this equation agreed with that observed in almost all growth phases. Furthermore, from the change of chlorophyll productivity and the relationship between D and E(x) expressed in this equation, it is assumed that E(x) involves the light energy directly utilized in photosynthesis in the cells and that which is converted into, e.g., heat. This equation also indicated that a maximum in the growth yield existed. Then the growth yield of 0.029 g/kcal obtained at the incident light of 1.46 or 2.63 cal/cm(2) . h was maximum (maximal conversion efficiency of light energy, 15.6%).These results indicate that this method of deriving the equation for the growth rate from this study is a useful procedure for obtaining bioengineering findings.     

Controlling light-use by Rhodobacter capsulatus continuous cultures in a flat-panel photobioreactor

The main bottleneck in scale-up of phototrophic fermentation is the low efficiency of light energy conversion to the desired product, which is caused by an excessive dissipation of light energy to heat. The photoheterotrophic formation of hydrogen from acetate and light energy by the microorganism Rhodobacter capsulatus NCIMB 11773 was chosen as a case study in this work. A light energy balance was set up, in which the total bacterial light energy absorption is split up and attributed to its destinations. These are biomass growth and maintenance, generation of hydrogen and photosynthetic heat dissipation. The constants defined in the light energy balance were determined experimentally using a flat-panel photobioreactor with a 3-cm optical path. An experimental method called D-stat was applied. Continuous cultures were kept in a so-called pseudo steady state, while the dilution rate was reduced slowly and smoothly. The biomass yield and maintenance coefficients of Rhodobacter capsulatus biomass on light energy were determined at 12.4 W/m(2) (400-950 nm) and amounted to 2.58 x 10(-8) +/- 0.04 x 10(-8) kg/J and 102 +/- 3.5 W/kg, respectively. The fraction of the absorbed light energy that was dissipated to heat at 473 W/m(2) depended on the biomass concentration in the reactor and varied between 0.80 and 0.88, as the biomass concentration was increased from 2.0 to 8.0 kg/m(3). The process conditions were estimated at which a 3.7% conversion efficiency of absorbed light energy to produced hydrogen energy should be attainable at 473 W/m(2).     

Absorption and Transfer of Light and Photoreduction Activities of Spinach Chloroplasts under Calcium Deficiency: Promotion by Cerium

Chloroplasts were isolated from spinach cultured in calcium-deficient, cerium-chloride-administered calcium-present Hoagland’s media or that of calcium-deficient Hoagland’s media and demonstrated the effects of cerium on distribution of light energy between photosystems II and I and photochemical activities of spinach chloroplast grown in calcium-deficient media. It was observed that calcium deprivation significantly inhibited light absorption, energy transfer from LHCII to photosystemII, excitation energy distribution from PSI to PSII, and transformation from light energy to electron energy and oxygen evolution of chloroplasts. However, cerium treatment to calcium-deficient chloroplasts could obviously improve light absorption and excitation energy distribution from photosystem I to photosystem II and increase activity of whole chain electron transport, photosystems II and I DCPIP photoreduction, and oxygen evolution of chloroplasts. The results suggested that cerium under calcium deficiency condition could substitute for calcium in chloroplasts, maintain the stability of chloroplast membrane, and improve photosynthesis of spinach chloroplast, but the mechanisms still need further study.     

The first living systems: a bioenergetic perspective.

The first systems of molecules having the properties of the living state presumably self-assembled from a mixture of organic compounds available on the prebiotic Earth. To carry out the polymer synthesis characteristic of all forms of life, such systems would require one or more sources of energy to activate monomers to be incorporated into polymers. Possible sources of energy for this process include heat, light energy, chemical energy, and ionic potentials across membranes. These energy sources are explored here, with a particular focus on mechanisms by which self-assembled molecular aggregates could capture the energy and use it to form chemical bonds in polymers. Based on available evidence, a reasonable conjecture is that membranous vesicles were present on the prebiotic Earth and that systems of replicating and catalytic macromolecules could become encapsulated in the vesicles. In the laboratory, this can be modeled by encapsulated polymerases prepared as liposomes. By an appropriate choice of lipids, the permeability properties of the liposomes can be adjusted so that ionic substrates permeate at a sufficient rate to provide a source of monomers for the enzymes, with the result that nucleic acids accumulate in the vesicles. Despite this progress, there is still no clear mechanism by which the free energy of light, ion gradients, or redox potential can be coupled to polymer bond formation in a protocellular structure.