我国沿海双唇形突海链藻的形态学研究

唇形突是海链藻中常见的一类突起, 其形态学特征和排列方式是重要的分类学依据。绝大多数海链藻只有一个唇形突, 两个唇形突的现象仅报道于极少数海链藻种类。我国关于双唇形突海链藻的报道较少。研究利用扫描电镜(SEM)技术, 对采自我国沿海海域的自然水样, 以及分离获得的单克隆培养藻株进行了形态学观察, 针对其中的海链藻属Thalassiosira Cleve种类开展了形态学的专题研究。报道了4个具有双唇形突的海链藻种类, 分别是有翼海链藻T. bipartita (Rattray) Hallegraeff、脆弱海链藻T. fragilis Fryxell、亨氏海链藻T. hendeyi Hasle &; Fryxell和维斯吉思海链藻T. visurgis Hustedt, 其中有3个为我国新记录种类: 脆弱海链藻、亨氏海链藻和维斯吉思海链藻。对每个种类的形态学特征、生活习性和生态分布进行了描述, 提供了扫描电镜照片, 对相似种类的形态学特征进行了比较研究, 分析了唇形突的变化类型及其分类学价值。     

我国沿海闭合突海链藻的形态学研究

闭合突是一类特殊的突起, 仅报道于少数海链藻种类, 其形态学特征和排列方式是重要的分类学依据。我国关于闭合突海链藻的报道较少。研究利用扫描电镜(SEM)技术, 对采自我国沿海海域的自然水样, 以及分离获得的单克隆培养藻株进行了形态学观察, 针对其中的海链藻属Thalassiosira Cleve种类开展了形态分类学的专题研究。报道了5个具有闭合突的海链藻种类, 分别是西达礁海链藻T. cedarkeyensis Prasad、偏心海链藻T. eccentrica (Ehrenberg) Cleve、伦德海链藻T. lundiana Fryxell、细孔海链藻T. punctigera (Castracane) Hasle和管状海链藻T. tubifera Fryxell, 其中有3个为我国新记录种类: 西达礁海链藻、细孔海链藻和管状海链藻。对每个种类的形态学特征和生境进行了描述, 提供了扫描电镜照片, 对相似种类的形态学特征进行了比较研究, 分析了突起特征的变化类型及其分类学价值。     

中国团藻科新记录属—— 板藻属(Platydorina)

在广东省深圳水库采集的浮游植物样品中发现团藻科1个单种属及其种：板藻属（Platydorina）、具尾板藻（Platydorina caudata Kofoid）。植物体扁平状马蹄形,微呈左旋;在马蹄形后端具3至5个胶质突起;由16或32个细胞在胶质基质中朝不同的方向排列成单层的群体,细胞球形或梨形,具2条等长鞭毛,细胞在群体两面交错排列;每个细胞具1个眼点;鞭毛基部具2个伸缩泡;色素体大型杯状,1个蛋白核位于杯状色素体的基部。无性繁殖通过亲体部分或全部细胞的反复分裂完成;有性生殖为异配生殖,形成厚壁休眠合子。     

多变鱼腥藻(Anabaena variabilis)藻胆体——类囊体膜光能传递的研究

多变鱼腥藻(Anabaena variabilis)藻胆体一类囊体膜的吸收峰位于678,624,490,438和418nm.当用580nm波长光激发藻胆体一类囊体膜中藻胆蛋白时,室温荧光峰位于662nm,在680nm附近有一肩;液氮温度荧光峰位于655,666,695和730nm.这说明藻胆蛋白捕获的光能能有效地传给叶绿素a.当用436nm波长光激发藻胆体一类囊性膜中叶绿素a时,室温荧光峰(?)于683nm;液氮温室荧光峰在730nm,另一小峰在695nm.表明叶绿素a捕获的光能不能传递给藻胆蛋白.藻胆体一类囊体膜放氧速率为245μmoleO_2/小时,毫克叶绿素,电境照片显示在类囊体膜上有大量藻胆体.用0.3M蔗糖,O.05M磷酸缓冲溶液洗藻胆体一类囊体膜,能使藻胆体与类囊体膜分开.对藻胆体与类囊体之间的光能传递进行了讨论.     

中国气生绿藻的新纪录属——细链藻属(Leptosira)

在对上海市树附生藻类的调查中,发现了我国一气生绿藻新纪录属——细链藻属Leptosira Borzi 1883。对该属及该属的一个新纪录种的主要形态学特征及生境特征进行了详细描述。     

我国北方岩溶泉域刚毛藻的系统发育及形态学研究(英文)

脆弱刚毛藻(Cladophora fracta)是一种大型丝状绿藻,生境分布广泛。然而,对于岩溶泉域分布的刚毛藻研究较少,它们的遗传多样性、生物地理亲缘性和生理特性都有待于深入研究。该研究对我国北方地区五个典型岩溶泉域的50个脆弱刚毛藻样本进行了形态学和分子系统学描述。主要研究目标:(1)对我国北方地区五个典型岩溶泉的刚毛藻生境进行描述;(2)根据形态学特征和分子序列对藻体进行鉴定;(3)探究生境对藻体生理特性的影响。结果表明:基于SSU和LSU序列的结果,发现所分析的50株刚毛藻个体为同一种,同时还发现了13个不同的核糖体基因型。基于SSU和LSU的系统发育树,刚毛藻属均未能形成单系分支,分布在三个不同的分支上。13个样本基因型在SSU和LSU树中的位置相似,与Cladophora vagabunda有很高的序列同源性,但是形态特征却差异很大。从显微结构结果来看,五个岩溶泉域采集到的刚毛藻在细胞直径上无显著差异,藻体的形态特征与脆弱刚毛藻相一致。但是,岩溶泉域采集的藻体细胞直径比文献报道中在湖泊和河流中采集的脆弱刚毛藻直径要大。另外,仅在两个地点(XA和ST)采集的标本中发现有假根状分枝。因此,基于形态学和分子序列的结果,将这五个泉域的刚毛藻鉴定为脆弱刚毛藻(Cladophora fracta)。     

赤潮水体中胶体物质对赤潮异弯藻(Heterosigma akashiwo)和中肋骨条藻(Skeletonema costatum)生长的影响

2004年2月9～10日在胶州湾发生的柔弱几内亚藻(Guinardia delicatula)赤潮期间分别在3个典型赤潮站位采集表层水样,利用过滤(0.7μm)和切向超滤(1000 Daltons)分离赤潮暴发水体中的胶体物质,分析了不同滤液及截留液的有机碳含量,并将赤潮异弯藻 (Heterosigma akashiwo)和中肋骨条藻(Skeletonema costatum)在<1000 Daltons的超滤液及具有不同含量胶体物质(1000 Daltons～0.7μm)的截留液中进行培养.结果发现在发生柔弱几内亚藻赤潮期间水体中的溶解有机碳浓度会增加,特别是胶体有机碳浓度会成倍增长;在不同胶体含量海水中培养的赤潮异弯藻的最大生长率μmax和最大生物量Bf与对照组相比会随着胶体含量的增加而显著增大,而中肋骨条藻的最大生长率μmax和最大生物量Bf与对照组相比会随着胶体含量增加而显著降低,表明柔弱几内亚藻赤潮水体中的胶体物质对赤潮异弯藻的生长起促进作用,而对中肋骨条藻的生长起抑制作用.这说明柔弱几内亚藻在增殖过程中所产生的胶体物质具有他感作用,会影响其它微藻的生长,从而可能对柔弱几内亚藻赤潮的形成起重要作用.     

镰刀藻属与伪镰刀藻属的超微结构比较研究

利用扫描电镜对华南沿海及澳大利亚分布的镰刀藻属（Falcula）和伪镰刀藻属（Pseudofalcula）硅藻进行了形态学观察。发现一中国新记录硅藻,即中间镰刀藻（F. media Voigt）;首次报道了半波镰刀藻（F. semiundulata Voigt）的超微形态结构;通过与透明伪镰刀藻（P. hyalina (Takano) Gómez, Wang & Lin）的比较进一步界定了两属的形态学差异。其中,二者顶纹区结构的差异最为显著：镰刀藻属的顶纹区由数条狭缝组成,而伪镰刀藻属的顶纹区为嵌入壳套的眼点且呈网格状结构。此外,明确了镰刀藻属物种多是大型海藻上的植表生硅藻,而伪镰刀藻属则为典型的动表生硅藻,其宿主为海洋桡足类。本文扩大了中间镰刀藻、半波镰刀藻和透明伪镰刀藻的地理分布区域,厘清了镰刀藻属和伪镰刀藻属的形态学划分依据。     

具尾蓝隐藻(Chroomonas caudata Geitler)研究──Ⅱ.藻蓝蛋白(Phycocyanin)的初步分析

初步分析了具尾蓝隐藻(Chroomonas caudata Geitler)的藻蓝蛋白,其吸收光谱为一双峰曲线,两个吸收峰分别为590nm和640nm。按A.N.Glazer等关于隐藻藻蓝蛋白分型的意见,具尾蓝隐藻的藻蓝蛋白属于Ⅱ型PC－645。     

EFFECT OF SILICATE LIMITATION ON VALVE MORPHOLOGY IN THALASSIOSIRA AND COSCINODISCUS (BACILLARIOPHYCEAE)1

Coscinodiscus radiatus Ehrenb. and Thalassiosira eccentrica (Ehrenb.) Cleve were grown in a silicate-limited chemostat at silicate concentrations below 1 μg-atoms · l^?1. The resulting abnormal valves of C. radiatus lacked a thickened ring around the foramina; their pore membranes were thinner and their loculi shallower than those in normal cells. Abnormal valves of T. eccentrica had a fasciculate areolae pattern; they lacked a silica covering over the foramina and some tangential areolae walls. Neither abnormal valve could be termed a new species.     

Changes in the Lipid Composition of Thalassiosira pseudonana during Its Life Cycle

The lipid and fatty acid (FA) compositions of a marine diatom alga Thalassiosira pseudonana grown in culture were investigated. The relative content of separate lipid classes and their FA composition varied during of the life cycle. During the periods of active cell division and resting cell production, the proportion of polar lipids, as the structural components of cell membranes, increased. Changes in the proportion of lipid classes resulted in shifts in the FA composition of total lipids. It is suggested that the structural components of photosynthetic and cells membranes accumulate in the resting cells. Thereby, a rapid cell growth and an extensive development of the species under favorable environmental conditions is provided.     

Electrophysiology of the marine diatom Coscinodiscus wailesii IV: types of non-linear current-voltage-time relationships recorded with single saw-tooth voltage-clamp experiments

Electrophysiological states of the marine diatom Coscinodiscus wailesii are known to change spontaneously in the temporal range of seconds. In order to assess the genuine current-voltage-time relationships of individual states in less than a second, voltage-clamp experiments have been carried out using single sweeps of saw-tooth shaped command voltages. This method is introduced with model calculations. Plotting the results in current-voltage coordinates provides convenient access to several electrophysiological entities, such as absence of drift (smoothly closed IV loops), membrane capacitance (by I jump at sign reversal of dV/dt), and ohmic conductances (in linear regions of the current-voltage relationship), as well as equilibrium voltage (internal intersection of capacitance-corrected, 8-shaped tracings) and coarse gating kinetics (rise or fall of capacitance-corrected I at sign reversal of dV/dt) of a voltage-sensitive ion conductance. From electrophysiological measurements with double-barreled glass-microelectrodes on C. wailesii, several distinct types of current-voltage loops are presented. Most of the data, including recordings from electrical excitation, can be interpreted as temporal relaxations of voltage-sensitive conductances for K⁺ and Cl⁻. A more detailed analysis of the effect of tetraethylammonium (TEA⁺) shows that 10 and 20 mM TEA⁺ inhibit the K⁺ conductance in C. wailesii only by up to about 20% but predominantly via a K⁺ outward rectifier. Received: 23 December 1998 / Revised version: 1 June 1999 / Accepted: 1 June 1999     

Structural and inhibition insights into carbonic anhydrase CDCA1 from the marine diatom Thalassiosira weissflogii

Carbonic anhydrases (CAs) catalyze with high efficiency the reversible hydration of carbon dioxide, an essential reaction for many biological processes, such as photosynthesis, respiration, renal tubular acidification, and bone resorption. Diatoms, which are one of the most common types of phytoplankton and are widespread in oceans, possess CAs fundamental for acquisition of inorganic carbon. Recently, in the marine diatom Thalassiosira weissflogii a novel enzyme, CDCA1, naturally using Cd in its active site, has been isolated and categorized in a new CA class, namely zeta-CA. This enzyme, which consists of three repeats (R1, R2 and R3), is a cambialistic carbonic anhydrase that can spontaneously exchange Zn or Cd at its active centre, presumably an adaptative advantage for diatoms that grow fast in the metal-poor environment of the surface ocean. In this paper we completed the characterization of this enzyme, reporting the X-ray structure of the last repeat, CDCA1-R3 in its cadmium-bound form, and presenting a model of the full length protein obtained by docking approaches. Results show that CDCA1 has a quite compact not symmetric structure, characterized by two covalently linked R1-R2 and R2-R3 interfaces and a small non-covalent R1-R3 interface. The three dimensional arrangement shows that most of the non-conserved aminoacids of the three repeats are located at the interface regions and that the active sites are far from each other and completely accessible to the substrate. Finally, a detailed inhibition study of CDCA1-R3 repeat in both cadmium- and zinc- bound form has been performed with sulfonamides and sulfamates derivatives. The results have been compared with those previously reported for other CA classes, namely alpha- and beta-classes, and correlated with the structural features of these enzymes.     

The effect of irradiance and irradiation time on the size of initial cells in vegetative cell enlargement of Coscinodiscus wailesii (Centrales, Bacillariophyceae) in culture

The effect of irradiance and irradiation time were examined on rates of pseudo-auxospore formation and the size of initial cells in vegetative cell enlargement of the giant diatom Coscinodiscus wailesii Gran in culture. The mean rate of pseudo-auxospore formation ranged from 25.9% to 47.8% between experimental incubation conditions. No significant difference was detected in rates among different irradiances and irradiation times, and parent cell sizes. However, the mean valve diameter of the initial cells of the diatom was affected by an interaction between the light conditions and the diameter of the parent cells. Initial cells size tended to be larger with combined conditions of higher irradiance levels and longer irradiation time. There appears to be a relationship (a steady increase, although not a straight line) between the total daily irradiance and the valve diameter of the initial cells. The mean valve diameter of initial cells from larger parent cells was significantly larger than those from smaller parent cells under the same light conditions.     

Autecological investigations on marine diatoms. 5:Coscinodiscus concinnus W. Smith andRhizosolenia setigera Brightwell

The cold oligo-eurytherm diatomsCoscinodiscus concinnus W. Smith andRhizosolenia setigera Brightwell were cultured to determine their best competitive position by growth. Comparison of their generation times with those of other diatoms indicate that they reach this position between 6°C and 12°C. Both species grew between –1.5°C and about 20°C. The experiments indicate thatC. concinnus flowerings are possible in a deep water column, during periods of high light intensities. The simultaneous death of species in the upper layer is also caused by high light intensities.C. concinnus appeared in two morphological forms; the normal voluminous form, and a flatter form with a few intercalary bands only, filled with large oil-droplets. The latter appeared at 0°C and below, and at the upper temperature limit for growth of about 19°C–20°C. The separation of nov. spec. fromC. concinnus based on the absence or presence of a hyaline area and intercalary bands as identification characteristics should be reconsidered.     

Effect of Si-status on diel variation of intracellular free amino acids in Thalassiosira weissflogii under low-light intensity

Twenty-one intracellular free amino acids were analysed during a 12-12 h light-dark cycle, on duplicate axenic cultures of Thalassiosira weissflogii (clone Actin, Provasoli-Guillard CCMP) under either Si-sufficient or Si-starved conditions. Total concentrations ranged between 40 and 165 fmol/cell. Total level as well as individual levels of amino acids decreased during the dark period, and GLN/GLU ratio was lower during the dark period. All these results were correlated with the light-dark carbon metabolism of the algae and related to the protein synthesis at night. The Si-starved cultures showed a lower total level of FAA compare to the Si-sufficient cultures, especially in the light period. Silica status of the cells affected more the metabolites of the dark respiration than the photorespiratory metabolites SER and GLY. Si deprivation induced higher range of ALA and VAL, and a decrease of the TCA metabolites GLU & ASP. Additionally, the relative percentage of ASP increased under Si starvation, at the expense of GLU, and this shift was emphasized in the dark period.     

WALL MORPHOGENESIS IN COSCINODISCUS WAILESII GRAN AND ANGST. I. VALVE MORPHOLOGY AND DEVELOPMENT OF ITS ARCHITECTURE1

The morphology of the valve of Coscinodiscus wailesii and the development of its siliceous architecture, studied in the SEM and TEM, is compared with valve formation in Thalassiosira eccentrica (Ehrenberg.) Cleve. Though the areolae-architecture of these two species differs in such that the cribrum is proximal and the foramen distal in T. eccentrica, and in C. wailesii the cribrum is distal and the foramen proximal, the formation of their complex loculate system is similar, displacing a centrifugal growth pattern with respect to the valve, and a proximal to distal, sequentially. During base layer formation a hitherto undescribed rib system outlines the prospective areolae. The vertical differentiation is in principle the same as in T. eccentrica and also the cribra are formed centripetally in relation to the areolae in both species. The location of the cribra at the proximal or distal side, therefore, seems to be of minor importance for the sequence of silica deposition. Variation in girdle bands is discussed with respect to cell division. The prophasic nuclear migration from the interphase position to the girdle bands, where mitosis is performed, seems to be necessary for triggering the formation of the unilateral cleavage furrow that later forms a cleavage ring with excentric position. The divided nuclei migrate with the ingrowing cleavage furrow to the center of the newly created protoplasmic surfaces to initiate valve formation.     

Photosynthetic oscillation in individual cells of the marine diatom <Emphasis Type="Italic">Coscinodiscus wailesii</Emphasis> (Bacillariophyceae) revealed by microsensor measurements

Oscillations with a period of 1–2 min in the rate of photosynthesis have been found in leaves of C₃ and C₄ land plants under invariant, saturating, light and carbon dioxide. This article reports the occurrence of similar oscillations with a period of 2–2.5 min in individual cells of the marine diatom Coscinodiscus wailesii. These oscillations were determined by measurements of both oxygen (oxygen microelectrode) and carbon dioxide (pH microelectrode) just outside the plasmalemma. These oscillations were found in less than 1% of the cells examined. The occurrence of oscillations in unicelluar diatoms rules out for these organisms hypotheses as to the origin of oscillations in land plant leaves that are based on cell–cell interactions.