微囊藻毒素降解菌S3的分子鉴定及其降解毒素的研究

对一株具有强降解微囊藻毒紊MC-LR能力的细菌S3进行了分子鉴定.测得该菌16S rDNA为1396bp,GenBank序列登录号为DQ836314.序列比对结果显示,该菌与类芽孢杆菌Paenibacillus validus的相似性达98%.微囊藻毒素降解实验结果表明,该菌能在以微囊藻毒素为唯一碳、氮源的培养基中生长,微囊藻毒紊在72h内减少78.3%,菌株S3的最适生长温度是30℃,最适生长pH值为7.0.     

改性蓝藻生物炭促进生物电化学系统阴极氢自养反硝化过程研究

以太湖蓝藻为原料制备不同种类的活性生物炭,并将其投入到生物电化学系统（BES）的阴极促进氢自养反硝化。通过扫描电镜、能谱仪和傅里叶红外光谱对未经改性（ABC-800）、硝酸改性（ABC-800N）和KOH改性（ABC-800K）3组蓝藻生物炭进行观察,并与不加入蓝藻生物炭的对照组进行比较,以考察生物炭促进BES生物阴极的反硝化过程中的电子传递机制。结果表明：ABC-800N表面的N、O元素含量最高,同时与电子传递能力及生物相容性相关的共轭醌、酮结构的丰度也最高;将蓝藻生物炭投加至BES的非生物阴极中可提高阴极的脱氮效率,ABC-800N投加量为0.5 g时,7 d内脱氮效率达到最高,为96.0%,而对照组仅为29.6%;高通量测序表明,ABC-800N组的优势菌属为Thauera、JGI_0001001_H03、Thiobacillus、Denitratisoma等。

     

铜绿微囊藻生长代谢的密度依赖性特征及分子机制

蓝藻水华是淡水湖库普遍面临的水环境问题,目前水华形成机制研究大多关注外界环境因素而忽略了藻类自身及群体的关键调节作用.因此,本文以初始细胞密度为单一变量,考察了不同初始细胞密度条件下蓝藻生长、营养物质利用、叶绿素、藻毒素、胞外分泌物随时间的变化情况.结果发现,初始细胞密度会影响铜绿微囊藻的环境适应性和生长情况,当接种密度≥1×10⁶ cell·mL^-1,铜绿微囊藻适应期消失,初始细胞密度从1×10⁵ cell·mL^-1增加至1×10⁷ cell·mL^-1,最高细胞密度增加了68%,生长速率提高了21%,并且叶绿素变化趋势与生长情况一致.胞外分泌物随初始细胞密度增加而逐渐增加,有利于蓝藻细胞聚集成膜.当初始细胞密度较低（1×10⁵ cell·mL^-1）时,单细胞藻毒素分泌量反而增加,以提高蓝藻的环境适应能力.在高初始密度（1×10⁷ cell·mL^-1）条件下,铜绿微囊藻主要通过上调丙酮酸代谢和碳代谢,促进细胞生长增殖.因此,细胞密度是影响铜绿微囊藻生长代谢的重要因素,在蓝藻水华形成过程中可能发挥重要作用,水华防治应当在细胞密度较低的阶段进行.     

Caspase-3在微囊藻毒素诱导的细胞凋亡中的作用

在已证实微囊藻毒素LR(MCLR)可以诱导大鼠肾细胞凋亡的基础上,采用荧光染料FAM标记的特异性的caspase-3的抑制剂来检测活细胞中caspase-3的酶活性,探讨caspase-3在MCLR诱导的细胞凋亡中所起的作用.结果表明,MCLR可以诱导caspase-3活性的增强.因此推测caspase-3在MCLR诱导的细胞凋亡中可能起重要作用.     

微囊藻毒素对束丝藻细胞生长和抗氧化系统的影响

为从活性氧(ROS)角度探讨微囊藻毒素(MC)导致藻类细胞死亡的机理及揭示藻细胞对MC诱发的氧化胁迫的响应机制,采用50和500μg·L-1的微囊藻毒素LR(MC-LR)处理束丝藻(Aphanizomenon sp. DC01)细胞,测定了细胞生长、细胞内活性氧(ROS)含量及抗氧化系统的变化.结果表明,50μg·L-1的MC-LR处理对藻细胞的生长无显著影响,而500μg·L-1的MC-LR处理可诱导藻细胞死亡.50μg·L-1的MC-LR处理的藻细胞ROS含量在处理第2d显著高于对照;但藻细胞能通过还原型谷胱甘肽(GSH)含量,超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPX)活性改变修复氧化损伤,使ROS水平在处理第3d恢复到对照水平.500μg·L-1的MC-LR处理可显著降低藻细胞GSH含量和SOD与GPX活性,刺激藻细胞生成过量的ROS;ROS在毒素处理4d后突然暴发,过量的ROS引起膜质过氧化,并最终导致藻细胞死亡。     

利用SPR技术测定湖水中微囊藻毒素

利用表面等离子共振(SPR)技术,建立了快速定量检测湖水中微囊藻毒素LR(MC-LR)的方法.将MC-LR共价偶联到表面等离子共振芯片表面,检测了芯片的稳定性,并利用免疫竞争抑制原理构建标准曲线,对湖水样品进行了检测.结果表明:制备的芯片信号稳定,50个循环相对标准偏差(RSD)为0.62%;该方法的最低检测浓度为0.25ng/mL,可作为水体中MC-LR的分析检测方法.     

时间分辨荧光免疫一步法检测微囊藻毒素的研究

利用稀土元素Eu³⁺ 标记微囊藻毒素偶联物MCLR-BSA,在固相包被二抗的微孔板上建立了微囊藻毒素的直接竞争时间分辨荧光免疫法.条件优化后Eu³⁺ 标记物的稀释度为1∶50,微囊藻毒素单抗的合适浓度为100 ng/mL.该法对微囊藻毒素检测的灵敏度为0.02 ng/mL,试剂的测量范围是0.05～10 ng/mL,回收率达到94％以上.     

Removal of Microcystins by Phototrophic Biofilms. A Microcosm Study (6 pp)

Background, Aims and Scope Microcystins (MCs) are a family of natural toxins produced by cyanobacteria (blue-green algae). As a result of eutrophication, massive cyanobacterial blooms occur more frequently and MCs represent important contaminants of freshwater ecosystems. Bacterial biodegradation is considered a main mechanism for MC breakdown in environmental conditions. While existing studies were mostly focused on MC biodegradation by planktonic bacteria, our experiments examined the fate and kinetics of MC degradation in river-originated phototrophic biofilms and investigated factors influencing the rate of MC removal. Methods The fate of dissolved MCs was studied in laboratory microcosms with different composition (containing water only, water with phytoplankton and/or phototrophic biofilms). Biofilms originated from river ecosystem were pre-incubated under various conditions (with/without presence of cyanobacterial biomass or model organic substrates: glucose and protein - casein). Changes in MC concentration (0-14 days) in water columns were measured by HPLC DAD after external additions of purified MCs (160 μg L-1, MC-LR and MC YR), and halftimes (t1/2) of MC removal were estimated. Results and Discussion The slow degradation of MC was revealed in tap water (t1/2 ~ 14 days) and river water without cyanobacteria (t1/2 ~ 8 days). Enhanced removal occurred in the presence of natural planktonic cyanobacteria (t1/2 ~ 44 h), most probably due to microorganisms associated with the biomass of cyanobacterial bloom. More rapid MC elimination occurred in the variants containing phototrophic biofilms, and was particularly pronounced at those biofilms pre-cultivated in the presence of cyanobacterial blooms (t1/2 ~ 20 h). Much slower removal was observed in the variants simulating possible substrate-dependent induction of microorganism metabolism (biofilms pre-incubated with glucose: t1/2 ~ 35 h, and casein: t1/2 ~ 80 h). After termination of experiments, total amounts of MCs accumulated in the biofilms were below 5% of the initial toxin level revealing significant biodegradation processes. Conclusion The microcosm studies contributed to understanding of the environmental fate of MCs and revealed a rapid biodegradation by phototrophic biofilms. The rate of MC elimination depends on history of biofilm community, previous contact with cyanobacteria seems to be a selective factor improving the biodegradation potential. Recommendation and Outlook Our results experimentally showed a positive role of biofilms in MC elimination during water treatment processes such as bank filtration or slow sand filtration, and could eventually serve for further research of biofilm-based technological applications for MCs removal in small-scale drinking water treatment facilities.     

用蛋白磷酸酶抑制法测定水体中的微囊藻毒素类物质

建立了一种灵敏的测定水体中微囊藻毒素类物质的方法。从鱼肝脏中分离的蛋白磷酸酶２Ａ被微囊藻毒素抑制，并且抑制与毒素剂量相关，抑制模式表现为典型的Ｓ型曲线。根据末知样品存在时蛋白磷酸酶的相对活力，可由本研究得出的标准曲线及公式，计算样品中可能存在的微囊藻毒素类物质。研究表明，在一年的观测周期内，即使没有可见的水华发生，东湖及鱼池中仍有可检测出微囊藻毒素类物质。     

Isolation, identification and characterization of an algicidal bacterium from Lake Taihu and preliminary studies on its algicidal compounds

In an effort to identify a bio-agent capable of controlling cyanobacterial blooms, we isolated a bacterial strain, A27, which exhibited strong algicidal activity against the dominant bloom-forming species of Microcystis aeruginosa in Lake Taihu. Based on 16S rRNA gene sequence analysis, this strain belongs to the genus Exiguobacterium. This is the first report of an algicidal bacterial strain belonging to the genus Exiguobacterium. Strain A27 exhibited algicidal activity against a broad range of cyanobacteria, but elicited little or no algicidal activity against the two green algal strains tested. The algicidal activity of strain A27 was shown to be dependent on the density of the bacteria and to have a threshold density of 1.5× 10⁶ CFU/mL. Our data also showed that the algicidal activity of strain A27 depended on different growth stages of Microcystis aeruginosa (exponential ≈ lag phase > early stationary) rather than that of the bacterium itself. Our results also suggested the algicidal activity of strain A27 occurred via the production of extracellular algicidal compounds. Investigation of the algicidal compounds revealed that there were at least two different algicidal compounds produced by strain A27. These results indicated that strain A27 has great potential for use in the control of outbreaks of cyanobacterial blooms in Lake Taihu.