The effects of Anabaena spiroides (Cyanophyceae) exopolysaccharide on copper toxicity to Simocephalus serrulatus (Cladocera, Daphnidae)

1. This work investigated the consumption of a microalgal (Anabaena spiroides) exopolysaccharide by the cladoceran Simocephalus serrulatus (Cladocera, Daphnidae) and its effect on copper toxicity. 2. Total organic carbon concentration was used to quantify the microalgal exopolysaccharide. Both copper‐complexed exopolysaccharides and copper‐free exopolysaccharides were taken up by S. serrulatus. 3. A reduction of free copper ions was obtained in the presence of A. spiroides exopolysaccharide. Copper toxicity (EC₅₀) and zooplankton concentrations were inversely correlated to exopolysaccharide concentration in experimental media. 4. An increase of free copper ions in experimental media was obtained after exopolysaccharide consumption, suggesting that S. serrulatus excreted copper to the surrounding environment.     

洱海螺旋鱼腥藻生长生理特性的初步研究

近年来,洱海正处于中营养水平向富营养湖泊的过渡阶段,蓝藻水华也频繁发生。本文作者在洱海大规模水华暴发期间,分离、纯化了水华优势种螺旋鱼腥藻,并对其生长生理特性进行了初步研究,以期为探讨洱海鱼腥藻水华发生的环境影响因素提供基础的参考资料。实验结果表明,氮含量1.5mmol/L、磷含量12µmol/L、光照强度30E/ m·s、pH值8－10及温度25℃时,螺旋鱼腥藻生长状况最好,生物量及相对生长速率较高。不同氮、磷浓度下的氮磷代谢活性表明：氮浓度在0－0.36mmol/L时,硝酸还原酶活性随着氮浓度的增加而增强;氮浓度在0.36－6 mmol/L时,酶活性由其生长状况决定,生长越好,酶活性越高。碱性磷酸酶受磷影响较大,随着磷浓度的增加其活性逐渐减弱,磷充足时,氮对其活性并无显著影响。此外,洱海螺旋鱼腥藻可在低的氮、磷浓度下生长,这与其氮磷代谢活性的调节作用有关。     

Development,Growth and Survivorship of Juvenile Calanoid Copepods on Diets of Cyanobacteria and Algae

Nauplii and immature copepodites of Boeckella triarticulata, B. hamata and B. dilatata were tested for their ability to survive and grow on monospecific diets of four species of filamentous cyanobacteria, Cyclotella (Cy) and Cryptomonas (Cr) at 2 mg dry weight 1⁻¹. Cr supported the development from nauplius to adult of all three calanoid species; complete development on other diets occurred only in B. dilatata on Cy and Anabaena oscillarioides (Ao). Differences between nauplii and copepodites of B. dilatata and B. hamata in survivorship and development on diets of Cy, Anabaena flos-aquae (Af), Ao and Nostoc sp. 2 (N2) imply ontogenetic shifts in resource utilization with developmental phase. Ranked in order of their ability to support the development of juvenile boeckellids the foods were Cr > Cy > Ao > N2 > Af > Nostoc calcicola = no food.     

Maintenance of heterocyst patterning in a filamentous cyanobacterium

In the absence of sufficient combined nitrogen, some filamentous cyanobacteria differentiate nitrogen-fixing heterocysts at approximately every 10th cell position. As cells between heterocysts grow and divide, this initial pattern is maintained by the differentiation of a single cell approximately midway between existing heterocysts. This paper introduces a mathematical model for the maintenance of the periodic pattern of heterocysts differentiated by Anabaena sp. strain PCC 7120 based on the current experimental knowledge of the system. The model equations describe a non-diffusing activator (HetR) and two inhibitors (PatS and HetN) that undergo diffusion in a growing one-dimensional domain. The inhibitors in this model have distinct diffusion rates and temporal expression patterns. These unique aspects of the model reflect recent experimental findings regarding the molecular interactions that regulate patterning in Anabaena. Output from the model is in good agreement with both the temporal and spatial characteristics of the pattern maintenance process observed experimentally.     

生物反应器培养转基因鱼腥藻的研究

在反应器中研究了转人TNF-α基因鱼腥藻7120(Anabaena sp．PCC7120,pDC-TNF)的培养。结果表明气升式反应器适合于转基因鱼腥藻的培养。气升式反应器中通气量和光照是主要的影响因素,观察到1L罐中最适通气量为60～75L／h,最适光照强度为1200lx,此时在25℃混养,光照时间／黑暗时间为12h／12h,15d生物量干重大于3g／L,TNF表达水平约占总可溶蛋白的22％,达到了摇瓶培养水平。实验发现添加维生素B1 300μg／L、B12 200μg／L和生物素4μg／L时,生产周期为12d,缩短20％,表达水平相同。培养过程通入含有5％CO2的空气,能促进生长,缩短生产周期,但收获生物量不受影响。从添加维生素和通入CO2的培养结果证明反应器中培养时,光照是限制性因素,当反应器系统一定时,最终生物量有一个最大值,如需进一步提高产量,必须设法改变光照系统。     

超声和高压对牛血清白蛋白结构的影响比较

目的：研究牛血清白蛋白经过超声和高压处理前后的结构变化,以及自由基清除剂对其结构变化的影响。为进一步研究细胞破碎和乳化蛋白时超声和高压处理对蛋白的影响提供参考。方法：将BSA溶液经过超声和高压处理,然后利用高效液相色谱（HPLC）、动态光散射（DLS）、非变性聚丙烯酰胺凝胶电泳（nondenaturing SDS PAGE）以及园二色谱（CD）等手段检测处理前后的结构变化。结果：发现超声使BSA严重聚集,加入自由基清除剂可以减少聚集的产生。而高压处理后的BSA未出现聚集,但二级结构发生了变化。结论：超声和高压这两种处理方法对蛋白损伤机理不同,所以选择合适的破碎方法要根据蛋白自身的性质而定。     

Modelling the effects of dams on freshwater fish distributions in Hokkaido, Japan

1. We examined the effects of habitat fragmentation caused by dams on freshwater fish species using a database of 7848 fish presence/absence surveys, conducted between 1953–2003 in Hokkaido, Japan. 2. A series of generalised linear models showed that for 11 of 41 taxa examined, the probability of occurrence had been influenced either negatively (eight taxa) or positively (three taxa) by the presence of a dam downstream from their habitat. 3. Maps of modelled predictions revealed that dams had had widespread negative impacts on certain taxa, while for other taxa the impact was limited to specific basins. Two of the three taxa whose probability of occurrence was increased in areas above dams have long been transplanted into reservoirs in Japan. 4. For four of the eight taxa whose probability of occurrence was reduced above dams and all three taxa whose probability of occurrence increased above dams, the temporal length of habitat isolation (i.e. the number of years between dam construction and sampling) was also a significant predictor of the probability of occurrence. This pattern indicates that these taxa experienced a gradual rather than an instantaneous population impact as a result of dam construction. 5. The eight taxa whose probability of occurrence was reduced as a consequence of dams all exhibit migratory life cycles. Although migratory taxa are probably more susceptible to the negative effect of dams, we could not detect significant relationships between migration life histories and the effect of fragmentation by dams. 6. These analyses enable stream and fisheries managers to quantify the impacts of habitat fragmentation because of dams for individual species. The spatially explicit nature of our analyses also enables identification of the areas of the impact at broad geographical scales. Using our results, managers can take effective conservation and restoration measures to predict, mitigate or remove the impact of dams. For example, our results can be used to prioritise dams for removal or to predict losses of biodiversity and ecosystem services in advance of dam construction.     

转基因鱼腥藻培养中培养液吸光度与生物量的关系

对转基因鱼腥藻Anabaena sp.PCC7120,培养液的吸光特性进行了研究,在可见光范围内,有5个吸收峰,波长分别为345nm,410nm,440nm,635nm,685nm,其中440nm是最大吸收波长,一定稀释度范围内,在各波长下,培养液中藻干重与吸光度均成正比,但不同培养基其干重－吸光度标准曲线不同,实验得到不同培养基的标准曲线,证明可以用比浊法测定转基因鱼腥灌培养过程的生物量。     

NOTE ESTABLISHMENT OF AXENIC CULTURES OF ANABAENA FLOS-AQUAE AND APHANOTHECE NIDULANS (CYANOBACTERIA) BY LYSOZYME TREATMENT

A new method using lysozyme for the production of axenic cultures of Anabaena flos-aquae De Brebisson and Aphanothece nidulans P. Richter was developed. Cyanobacterial growth was not inhibited at concentrations up to 1.2 g·L⁻¹ of lysozyme, whereas the growth of heterotrophic bacteria was suppressed. At concentrations up to 0.8 g·L⁻¹ of lysozyme, ampicillin caused a reduction of heterotrophic bacteria. The axenic cultures of these strains were acquired through a simple treatment using 1.0 g·L⁻¹ of lysozyme without ampicillin. These cyanobacteria resisted digestion by lysozyme at our experimental concentrations, whereas bacteria were digested selectively. This method of purification seems to be especially useful with cyanobacterial species that are sensitive to antibiotics or other germicidal agents.     

Patchy distribution of a fluvial sculpin,cottus nozawae, in the gakko river system at the southern margin of its native range

The distribution pattern of the freshwater sculpin,Cottus nozawae, was investigated in the Gakko River system, Tohoku District, northern Japan, that region representing the southern limit of the species distribution.C: nozawae was not found in the lower sections of the river, being instead restricted mainly to the upstream segments of some tributaries. The relationships between habitat variables and density ofC. nozawae analysed at reach scale, revealed that fish density increased with cover area, decreasing stream width and lower maximum water, temperature. Additionally, maximum water temperature was the best predictor of fish density according to stepwise multiple regression analysis. These data indicated that tributary populations ofC. nozawae were isolated from thermally unsuitable environments. Accordingly,C. nozawae was distributed patchily in headwater streams of this river system, in contrast to those on Hokkaido Island, where the species is distributed continuously throughout middle to upper stream courses.     

葡萄糖浓度对转人肿瘤坏死因子-α鱼腥藻IB02培养过程的影响

目的：通过在培养基中添加葡萄糖的方法,提高转基因鱼腥藻的产量和人肿瘤坏死因子（hTNF）-α的表达率。方法：在葡萄糖浓度为0～300mmol／L的范围内,进行了转hTNF-α鱼腥藻IB02的摇瓶混合营养培养,用比浊法和酶联免疫法测定转基因鱼腥藻的生长和hTNF-α的表达。结果：添加葡萄糖的藻液最高生长密度是未添加葡萄糖的3．5倍,且hTNFa的表达率也提高至4倍。结论：在各种葡萄糖浓度下,葡萄糖的利用都不明显。     

Characterization of HetR protein turnover in Anabaena sp. PCC 7120

The hetR gene plays an important role in heterocyst development and pattern formation in heterocystous cyanobacteria. The hetR gene from Anabaena sp. PCC 7120 was overexpressed in Escherichia coli. Antibodies raised against the recombinant HetR protein (rHetR) were used to characterize metabolism of the HetR of Anabaena sp. PCC 7120 in vivo. HetR was present at a low level when Anabaena sp. PCC 7120 was grown in the presence of combined nitrogen. Shifting from nitrogen repletion conditions to nitrogen depletion conditions led to a two fold increase of HetR in total cell extracts, and most of HetR was located in heterocysts. The amount of HetR in total cellular extracts increased rapidly after shifting to nitrogen depletion conditions and reached a maximum level 3 h after the shift. Isoelectrofocusing electrophoresis revealed that the native HetR had a more acidic isoelectric point than did rHetR. After combined nitrogen was added to the nitrogen-depleted cultures, the degradation of HetR depended on culture conditions: before heterocysts were fully developed, HetR was rapidly degraded; after heterocysts were fully developed, HetR was degraded much more slowly. The distribution of HetR in other species of cyanobacteria was also studied. Received: 24 June 1997 / Accepted: 5 December 1997     

利用鱼腥藻作为饲料的研究

鱼腥藻粉作为肉鸡、全雌鲤、青虾和对虾的饲料研究结果表明:2％的鱼腥藻粉替代鱼粉作为肉鸡饲料试验,肉鸡的个体平均增重效果与对照相当,屠宰率、半净膛率和全净膛率都有所提高;同时还具有改善肉质色泽的效果。对重金属的含量分析发现,食鱼腥藻的鸡除锌的含量略高外,铜、铁、锰、镉及铝的含量都低于对照组。添加2％的鱼腥藻粉在网箱中进行小试和大面积试验,结果都表明鱼腥藻粉对全雌鲤的生长有明显的效果,并能提高全雌鲤鱼种的成活率和降低饵料系数,利用鱼腥藻粉配合饲料在网箱和大面积养殖青虾试验表明,具有促进生长,提高产量的作用.对虾试验结果表明,在饵料中添加2％的鱼腥藻粉,饲喂45d后,对虾的体长增加了14.49％;体重增加了10.43％。这些研究结果表明利用鱼腥藻作为家禽及水产养殖动物的饲料具有相当大的应用前景。