Microbial biodegradation of microcystin-RR by bacterium Sphingopyxis sp. USTB-05

A strain,USTB-05,isolated from Lake Dianchi,China,degraded the cyanobacterial toxin microcystin-RR(MC-RR) at the rate of 16.7 mg/L per day.Analysis of 16S rDNA sequence showed that the strain was Sphingopyxis sp.Enzymatic degradation pathways for MC-RR by Sphingopyxis sp.USTB-05 were identified.Adda-Arg peptide bond of MC-RR was cleaved and then a hydrogen and a hydroxyl were combined onto the NH 2 group of Adda and the carboxyl group of arginine to form a linear molecule as intermediate product within the ...     

微囊藻毒素在细长聚球藻中的积累及其毒性效应

用 100μg/L 的微囊藻毒素(MC-RR)处理细长聚球藻,研究了 MC-RR 在藻细胞中的积累及其对细长聚球藻的生长和抗氧化系统的影响.结果表明,MC-RR 能在细长聚球藻中迅速积累,而细长聚球藻具有较强的降解 MC-RR 的能力,MC-RR 对细长聚球藻的生长具有显著的抑制作用;MC-RR 处理后,活性氧(ROS)和膜脂过氧化产物丙二醛(MDA)含量明显升高,还原型谷胱甘肽(GSH)含量和谷胱甘肽 S-转移酶(GST)、谷胱甘肽过氧化物酶(GPX)活性则有一个先降后升的变化.以上结果说明,细长聚球藻细胞在 MC-RR 处理下,膜脂过氧化加剧,受到氧化胁迫;GSH、GST、GPX 在清除活性氧,抵抗 MC-RR 的毒性伤害中发挥着关键的作用.     

微囊藻毒素-RR对烟草细胞活力及营养生理的影响

采用0.1,1.0,10.0μg/mL的微囊藻毒素-RR(MC-RR)处理烟草BY-2悬浮细胞,测定了细胞活力、细胞内蛋白质含量、可溶性糖含量、硝态氮含量及总磷含量,并且检测了酸性磷酸酶(ACP)的活力变化情况.结果表明,中、高浓度毒素处理细胞2d后,细胞活力及蛋白质含量与对照相比均显著下降.高浓度MC-RR处理降低了胞内可溶性糖的含量,暴露2d后仅为对照的45.57%;低浓度MC-RR处理在后期增加了胞内可溶性糖含量.高浓度毒素处理细胞4d后,细胞内硝态氮含量显著低于对照;中、低浓度毒素处理细胞7d后降低了胞内硝态氮含量.3组毒素处理均降低了胞内总磷含量,到实验结束时,低、中、高浓度处理组的胞内磷含量分别为对照的74.98%、76.47%和84.00%.3组处理组ACP活力与对照相比呈现先降低后升高的趋势.     

First report of microcystin production in Microcystis smithii Komrek and Anagnostidis(Cyanobacteria) from a water bloom in Eastern China

A water bloom sample collected from Lake Dishui in Shanghai was characterized.The morphological identification showed that Micorcystis wesenbergii and Micorcystis smithii were the main component of the bloom.Five strains of M.smithii were successfully isolated.Their 16S rRNA gene sequences based phylogenetic tree showed that the five strains of M.smithii intermixed with strains of other morphospecies in Microcystis.A fragment of mcy gene encoding for microcystin synthetase was detected in one of the five M....     

不同波段紫外光对微囊藻毒素光降解的影响

为优化光降解法去除饮用水中的微囊藻毒素,分别用UVA(l=300～400nm)和UVC(l=253.7nm)2种紫外光源研究了紫外光波长对MC-RR降解效率的影响.结果表明,不同波段的紫外光具有不同的催化效率和降解中间产物.在UVA下照射12h后,MC-RR仍有30%～50%残余,同时产生2种几何异构体4(Z)-Adda-MC-RR和6(Z)-Adda-MC-RR,且二者在整个反应过程中保持恒定的比例.而在UVC下,MC-RR除生成2种异构体外,还生成中间产物[三环-Adda]MC-RR,在0.850mW/cm2光强下照射60min后,这些中间产物随MC-RR一起基本消失.两种情况下,MC-RR浓度随时间的变化均可用二级反应速率方程描述,表观反应速率常数(k)均随着光强度的增加而增大.尽管UVC强度仅为UVA的10%,但MC-RR在UVC下的反应速率常数却比UVA下高了近2个数量级.这表明,利用光降解技术去除饮水中的微囊藻毒素宜选用UVC光源.     

微囊藻毒素-RR的提取和臭氧氧化降解

在对采自云南滇池水华蓝藻细胞中的微囊藻毒素-RR(microcystin-RR,MC-RR)提取并发现其含量达到0.19mg/g(干重)的基础上,重点研究了臭氧氧化降解所提取的MC-RR。结果表明,当反应体系中臭氧浓度为5.7 mg/L时,初始浓度1.9 mg/L的MC-RR在15 min内被完全降解。利用HPLC/ESI/MS对提取的MC-RR及其氧化降解产物质荷比测定发现,降解前MC-RR的质谱图中出现特征离子m/z=1 038.7、m/z=519.8以及m/z=135.0。而降解后的产物质谱图中只有Adda基团中带苯环结构化合物(C9H10O)的特征离子峰m/z=135.0存在,其他2个离子峰完全消失。由此推断反应体系中MC-RR(m/z=1 038.2)在大量臭氧及其.OH自由基全面攻击下,分子结构中Adda基团以及单环结构中的不饱和双键直接被氧化而发生断链,最终形成小分子的有机物。     

不同磷源及其浓度对铜绿微囊藻生长和产毒的影响

研究了以低浓度磷酸氢二钾和β-甘油磷酸钠为外加磷源时铜绿微囊藻生长及藻毒素产生的规律.通过分析铜绿微囊藻生长过程中细胞数量、培养基和藻细胞中总磷含量、培养基pH及微囊藻毒素-LR和微囊藻毒素-RR的含量,确定了2种磷源对铜绿微囊藻生长及胞内藻毒素含量的变化规律.结果显示,以β-甘油磷酸钠为磷源时,培养过程中藻细胞数及藻细胞内毒素含量均低于以磷酸氢二钾为磷源时的藻细胞数及藻细胞内毒素含量,表明在低浓度范围内磷酸氢二钾比β-甘油磷酸钠更能促进藻的生长,同时也能促进胞内藻毒素的生成.     

高效液相色谱法检测水中5种微囊藻毒素

使用Agilent1260型高效液相色谱仪,建立定量测定天然水体中5种微囊藻毒素（MC-RR、YR、LR、LA、LY）的分析方法。比较甲醇/三氟乙酸（TFA）水溶液与甲醇/磷酸两种流动相体系,待测物质的响应程度,结果发现,TFA作为缓冲溶液时,基线较磷酸稳定,因此,选择甲醇/TFA水溶液作为流动相。比较不同TFA体积比例,待测物质的分离程度,结果显示,甲醇/0.02%的TFA水溶液作为流动相时,5种MCs含量的分离度较好。比较等度和梯度洗脱条件,发现,梯度洗脱条件5种MCs的分离度较等度洗脱条件好。该方法 MC-RR、YR、LR、LA、LY的最低检出限（LOD）分别为0.015、0.035、0.018、0.032和0.026μg/L,最低定量限（LOQ）分别是0.049、0.117、0.062、0.106和0.086μg/L。在0.10～1.50μg/mL的线性范围内,相关系数R2≥0.99,实际水样回收率为73.9%～103.3%。     

First report of microcystin production in Microcystis smithii Komárek and Anagnostidis (Cyanobacteria) from a water bloom in Eastern China

A water bloom sample collected from Lake Dishui in Shanghai was characterized. The morphological identification showed that Micorcystis wesenbergii and Micorcystis smithii were the main component of the bloom. Five strains of M. smithii were successfully isolated. Their 16S rRNA gene sequences based phylogenetic tree showed that the five strains of M. smithii intermixed with strains of other morphospecies in Microcystis. A fragment of mcy gene encoding for microcystin synthetase was detected in one of the five M. smithii strains (CHAB 2183), indicating its potential of microcystin production. High performance liquid chromatography analysis confirmed M. smithii CHAB 2183 to produce microcystin-RR as 1550 g per gram dry weight cells. The present investigation, for the first time, reported the isolated strains of M. smithii and microcystin production from M. smithii.