滇池沉积物菌群对微囊藻毒素的厌氧生物降解

好氧微生物降解已经被证明是微囊藻毒素(MC)自然转化的主要途径,但是厌氧降解的作用尚不明确.为了揭示这一降解过程,研究了滇池沉积物中混合菌群在厌氧条件下对MCLR的降解能力,并考察了环境因素和外加营养源对该过程的影响.结果表明,厌氧条件下MCLR在2 d内从5 mg/L迅速降解到检测限以下,说明该菌群在厌氧条件下对MCLR具有较强的降解能力,并且可以利用MCLR作为唯一氮源.在实验温度范围内,MCLR的降解速率随着温度的升高而增大.酸性条件下MCLR的厌氧降解缓慢(pH=5.0)甚至停止(pH=3.0),

美姑脊蛇Achalinus meiguensis线粒体基因组全序列及系统发育地位研究

报道了美姑脊蛇Achalinus meiguensis线粒体基因组全序列.美姑脊蛇线粒体全序列长17239bp,由22个tRNA,2个rRNA和13个蛋白质基因及2个非编码的控制区或D-loop组成,存在着基因重排现象.对已报道蛇类线粒体基因组全序列进行比对分析后,发现一些蛇类线粒体基因组进化规律:双控制区现象在爬行动物进化历史中独立地发生,有不同的演化历史;tRNA假基因是在真蛇下目(Caenophidia)中进化形成的;TΨC臂的相对较短(一般少于5bp)和缺失"DHU"臂造成蛇类tRNA较短.通过M

湖北浮桥河水库浮游植物初级生产力及其管理

浮桥河水库浮游植物水柱日生产量变幅为0．34-4．99 g/(m~2-d),最低值出现在下游冬季,最高值出现在中游秋季,年平均值2．75 g/(m~2·d)．季节变化:秋季＞夏季＞春季＞冬季,与浮游植物叶绿素a含量和生物量的季节变化一致;水平分布:中游略高于上游,下游最低,与浮游植物叶绿素a含量的水平分布完全一致．表层日生产量占水柱日生产量53．81％．与1980年同期相比,浮游植物初级生产力增加了1．2倍．分析表明,磷含量增加是浮游植物初级生产力提高的关键因子．应用能量收支法估算浮桥河水库鲢鳙渔产潜力为

鲤病毒病原的感染性测定

为查明养殖鲤(Cyprinus carpio)突然大批发病死亡的原因,对鲤病样品进行了细胞攻毒、空斑测定、电镜观察,以及鱼体感染等实验。先以患病鲤的组织匀浆液,经过滤后,分别接种到草鱼鳍条细胞(GCF)、鲤上皮瘤细胞(EPC)等14种培养细胞中。利用倒置显微镜观察显示,在1~2 d内,该病鱼组织匀浆液可使其中9种细胞出现典型的细胞病变。收集出现病变的细胞液(即病毒悬液),进一步进行病毒滴度检测、空斑测定和鱼体感染实验。结果显示,在GCF细胞上的病毒滴度为107.3TCID50/mL;在FHM,TSB和GC

长江天鹅洲故道江豚的集群规模及其时空分布

2 0 0 1年 5月至 2 0 0 2年 4月 ,选择使用岸上定点观察、流动观察和水上流动观察 3种观察方式 ,对长江天鹅洲故道内约 2 0头江豚的集群状况进行了一个周年的监测 ,共观察到江豚集群 5 88次。结果表明 :天鹅洲故道内江豚以集群的方式迁移和活动 ,集群规模从 2— 2 0头不等 ,一般分成 2个 9— 11头规模的亚群体 ,2个亚群体活动范围相对独立 ,其活动主要为D区和H区。每个亚群体又常分成规模较小的核心群体 ,其中 3头集群最多。一年中春、秋和冬季江豚集群状况基本相同 ,而夏季有所

雌核发育银鲫两个不同品系线粒体DNA比较

于 1 996年 4月在中国科学院水生生物研究所关桥实验场取得银鲫E系 ( 8♀ ,2♂ )和D系 ( 9♀ ,1♂ )的卵巢 (♀ )或肝脏 (♂ )组织 ,分离纯化其线粒体DNA ,以此为材料 ,用 2 5种限制性内切酶分析了银鲫这两个雌核发育系的线粒体DNA ,构建了两系鱼mtDNA的 1 9种酶 41个位点的酶切图谱。统计比较酶切片段的大小 ,发现 5种内切酶 (AvaⅡ ,BamHⅠ ,BglⅠ ,SphⅠ ,XbaⅠ )酶切位点在两个雌核发育系间存在差异。这些多态性 ,既可以作为区分两个雌核发

中华绒螯蟹对苦草生境的依赖与破坏

确定浅水草型湖泊水草资源对放养中华绒螯蟹的承载量是探明水草多元功能的途径之一。本研究通过构建中华绒螯蟹栖息与生长所需的小生境,观察和分析了蟹-草之间的相互关系。试验结果显示苦草对放养中华绒螯蟹的承载量为1.08ind/100g/m~2,中华绒螯蟹的生长比速SGR(％/day)与其对苦草的拥有量Vp(g/m~2/ind)呈正相关,即SGR=0.464+0.003Vp。中华绒螯蟹特别是雄蟹对苦草的影响主要表现为破坏性,破坏率VD(g/ind/m~2/d)与雌、雄蟹的放养密度(S_F,S_m,ind/m~2)有

六种鱼腥藻在大量培养中的生产率和适应性与营养成分比较

连续两年对鱼腥藻的六个品系进行了大量培养比较研究,在长江中下游气候条件下,HB1042和HB1105具有稳定的生产性能,5月下旬至九月中旬123d内,平均有效生长分别为114和100d;其次是HB1058,HB686和HB1017,平均有效生长天分别为73,58和71d;HB13适应性较差。生物量生产率在5月下旬、6月中旬至9月中旬较高,除HB13外,平均都在10g干重/m~2/d以上或接近10g/m~2/d。在不同的季节它们表现出了各自的最高生物量生产率。据此,提出了逐月逐旬采取藻种搭配生产,以获得最高

利用底栖动物监测严家湖农药污染

本文报道了严家湖氧化塘建成前后底栖动物群落变化,共发现寡毛类12种,水生昆虫幼虫15种,软体动物8种,其他动物2种。讨论比较3种监测方法:(1)依据底栖动物群落结构各大类的比例,提出了六级标准;(2)用群落的多样性指数,由Shannon和Weaver的公式计算,并结合化学数据比较,提出D=0,D<1,D=>1—2,D=>2—3.5,D=>3.5—5,D>5六级评价;(3)用底栖动物的残留物积累,分析不同污染带的动物(Limnodrilus hoffmeisteri,Glyptotendipes sp.,B

Influence of dew on biomass and photosystem II activity of cyanobacterial crusts in the Hopq Desert, northwest China

Dew is an important water source for desert organisms in semiarid and arid regions. Both field and laboratory experiments were conducted to investigate the possible roles of dew in growth of biomass and photosynthetic activity within cyanobacterial crust. The cyanobacteria, Microcoleus vaginatus Gom. and Scytonema javanicum (Kutz.) Born et Flah., were begun with stock cultures and sequential mass cultivations, and then the field experiment was performed by inoculating the inocula onto shifting sand for forming cyanobacterial crust during late summer and autumn of 2007 in Hopq Desert, northwest China. Measurements of dew amount and Chlorophyll a content were carried out in order to evaluate the changes in crust biomass following dew. Also, we determined the activity of photosystem II(PSII) within the crust in the laboratory by simulating the desiccation/rehydration process due to dew. Results showed that the average daily dew amount as measured by the cloth-plate method (CPM) was 0.154 mm during fifty-three days and that the crust biomass fluctuated from initial inoculation of 4.3 mu g Chlorophyll a cm(-2) sand to 5.8-7.3 mu g Chlorophyll a cm(-2) crust when dew acted as the sole water source, and reached a peak value of approximately 8.2 mu g Chlorophyll a cm(-2) crust owing to rainfalls. It indicated that there was a highly significant correlation between dew amounts and crust moistures (r = 0.897 or r = 0.882, all P < 0.0001), but not a significant correlation between dew and the biomass (r = 0.246 or r = 0.257, all P > 0.05), and thus concluded that dew might only play a relatively limited role in regulating the crust biomass. Correspondingly, we found that rains significantly facilitated biomass increase of the cyanobacterial crust. Results from the simulative experiment upon rehydration showed that approximately 80% of PSII activity could be achieved within about 50 min after rehydration in the dark and at 5 degrees C, and only about 20% of the activity was light-temperature dependent. This might mean that dew was crucial for cyanobacterial crust to rapidly activate photosynthetic activity during desiccation and rehydration despite low temperatures and weak light before dawn. It also showed in this study that the cyanobacterial crusts could receive and retain more dew than sand, which depended on microclimatic characteristics and soil properties of the crusts. It may be necessary for us to fully understanding the influence of dew on regulating the growth and activity of cyanobacterial crust, and to soundly evaluate the crust's potential application in fighting desertification because of the available water due to dew. (C) 2009 Published by Elsevier Ltd.

Outer membrane proteins induced by iron deficiency in Anabaena sp PCC 7120

Iron deficiency can induce cyanobacteria to synthesize siderophore receptor proteins on the outer membrane to enhance the uptake of iron. In this study, an outer membrane of high purity was prepared from Anabaena sp. PCC 7120 based on aqueous polymer two-phase partitioning and discontinuous sucrose density ultra-centrifugation, and the induction of outer membrane proteins by iron deficiency was investigated using 2-D gel electrophoresis. At least. five outer membrane proteins were newly synthesized or significantly up-regulated in cells transferred to iron-deficient conditions, which were all identified to be siderophore receptor proteins according to MALDI-TOF-MS analyses. Bacterial luciferase reporter genes luxAB were employed to monitor the transcription of the encoding genes. The genes were induced by iron deficiency at the transcriptional level in different responsive modes. Luciferase activity expressed from an iron-regulated promoter may be used as a bioreporter for utilizable iron in natural water samples. (C) 2009 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.

Methane and carbon dioxide fluxes from a shallow hypereutrophic subtropical Lake in China

Up to now, there have been few studies in the annual fluxes of greenhouse gases in lakes of subtropical regions. The fluxes of methane (CH4) and carbon dioxide (CO2) across air-water interface were measured in a shallow, hypereutrophic, subtropical Lake Donghu (China) over a year cycle, using a static chamber technique. During the year, Lake Donghu emitted CH4 and CO2; the average flux of CH4 and CO2 was 23.3 +/- 18.6 and 332.3 +/- 160.1 mg m(-2) d(-1), respectively. The fluxes of CH4 and CO2 showed strong seasonal dynamics: CH4 emission rate was highest in summer, remaining low in other seasons, whereas CO2 was adsorbed from the atmosphere in spring and summer, but exhibited a large emission in winter. Annual carbon (C) budget across air-water interface in Lake Donghu was estimated to be 7.52 +/- 4.07 x 10(8) g. CH4 emission was correlated positively with net primary production (NPP) and temperature, whereas CO2 flux correlated negatively with NPP and temperature; however, there were no significant relationships between the fluxes of CH4 and CO2 and dissolved organic carbon, a significant difference from boreal lakes, indicating that phytoplankton rather than allochthonous matter regulated C dynamics across air-water interface of subtropical lake enriched nutrient content. (c) 2005 Elsevier Ltd. All rights reserved.

Mode Characteristics for Square Resonators With a Metal Confinement Layer

Microsquare resonators laterally confined by SiO2/Au/air multilayer structure are investigated by light ray method with reflection phase-shift of the multiple layers and two-dimensional (2-D) finite-difference time-domain (FDTD) technique. The reflectivity and phase shift of the mode light ray on the sides of the square resonator with the semiconductor/SiO2/Au/air multilayer structure are calculated for TE and TM modes by transfer matrix method. Based on the reflection phase shift and the reflectivity, the mode wavelength and factor are calculated by the resonant condition and the mirror loss, which are in agreement well with that obtained by the FDTD simulation. We find that the mode factor increases greatly with the increase of the SiO2 layer thickness, especially as d < 0.3 mu m. For the square resonator with side length 2 mu m and refractive index 3.2, anticrossing mode couplings are found for confined TE modes at wavelength about 1.6 mu m at d = 0.11 mu m, and confined TM modes at d = 0.71 mu m, respectively.

Resonant Enhanced Wave Filter and Waveguide via Surface Plasmons

The authors present an analysis of plasmonic wave filter and curved waveguide, simulated using a 2-D finite-difference time-domain technique. With different dielectric materials or surface structures located on the interface of the metal/dielectric, the resonant enhanced wave filter can divide light waves of different wavelengths and guide them with low losses. And the straight or curved waveguide can confine and guide light waves in a subwavelength scale. Within the 20 mu m simulation region, it is found that the intensity of the guided light at the interface is roughly four times the peak intensity of the incident light.

Analysis of mode characteristics for equilateral triangle semiconductor microlasers with imperfect boundaries

The influence of imperfect boundaries on the mode quality factor is investigated for equilateral-triangle-resonator (ETR) semiconductor microlasers by the finite difference time domain technique and the Pade approximation with Baker's algorithm. For 2-D ETR with a refractive index of 3.2 and side length of 5 mum, the confined modes can still have a quality factor of about 1000 as small triangles with side length of 1 mum are cut from the vertices of the ETR. For a deformed 5 mum ETR with round vertices and curve sides, the simulated mode quality factors are comparable to the measured results.