Tests for the toxicity assessment of cyanobacterial bloom samples

Cyanobacterial (blue-green algal) blooms are one of the common consequences of the increasing eutrophication of surface waters. The production of cyanobacterial toxins and their presence in drinking and recreational waters represents a growing danger to human and animal health. Due to a lack of toxin standards and to resource limitations on the wide-scale use of analytical methods (e.g., high-performance liquid chromatography, enzyme-linked immunosorbent assay (ELISA)) in cyanobacterial toxin monitoring, it is necessary to assess and to develop additional methods for their detection and estimation. Microbiotests using invertebrates offer a possible approach for the inexpensive and straightforward detection and assessment of cyanobacterial bloom toxicity. Three microbiotests with: Thamnocephalus platyurus, Daphnia magna, and Spirostomum ambiguum were examined with bloom samples containing hepatotoxic microcystin-LR and up to five additional microcystin variants. Two kinds of cyanobacterial bloom sample preparations were tested: crude extracts (CE) and purified extracts (PE). The highest toxicity was found when CE was used for microbiotests. The sensitivity of microorganisms decreased from S. ambiguum to T. platyurus and to D. magna. A statistically significant correlation was found between microcystin concentration and T. platyurus biotest, and between mouse bioassay and S. ambiguum results. Addition of Me2SO (1%, v/v) is a possible method to increase the sensitivity of the microorganisms for microcystin-LR.     

微囊藻毒素污染及其促肝癌作用研究进展

淡水水体的富营养化导致了蓝藻水华的普遍发生,微囊藻毒素是由蓝藻的部分藻属产生的环肽化合物,具有毒性大、分布广、结构稳定等特性,从而成为水环境中的重要潜在危害物质。微囊藻毒素已被证明具有明显的肝毒性,是肝肿瘤的促进剂之一。本文就微囊藻毒素的污染现状、肝毒性作用及其促肝癌机制等方面的研究进展进行了综述。     

微囊藻毒素及其毒性研究进展

微囊藻毒素是富营养化淡水水体中最常见的藻类毒素,它是一类具有多种异构体的环状多肽物质。由于其毒性大、分布广,从而成为水环境中的重要潜在危害物质。作者总结了微囊藻毒素的分子结构、理化性质及污染现状,并综述了有关其毒性及作用机理的国内外最新研究进展。     

Production of drinking water from raw water containing cyanobacteria--pilot plant studies for assessing the risk of microcystin breakthrough

Toxins in cyanobacteria are a recognized risk in the treatment of drinking-water treatment. Cyanotoxins can occur in two modifications: cell bound and dissolved in water. The process of toxin release may occur naturally, but it also may be induced through the processes of drinking-water treatment. Both causes of release are relevant to the safety of drinking water. This study investigated cyanotoxin release and elimination through different treatment trains in systematic pilot-scale studies with water from the Weida Reservoir, in Thuringia, Germany. The Weida Reservoir is a dimictic mesoeutrophic reservoir typical for a number of mountainous areas in Europe, with Planktothrix rubescens as the dominant phytoplankton species, and shows a characteristic seasonal pattern of population development and microcystin occurrence. To assess the risk of microcystin breakthrough, the pilot-scale results as well as results of laboratory-scale experiments were used for developing a kinetic model of toxin release in relation to elimination. By calculating removal efficiency of total microcystins (cell bound and dissolved) for different treatment trains, raw water quality was related to the quality targets for finished water, and breakthrough risks could be calculated for given treatment trains and varying cyanobacterial population densities in the reservoir.     

Species- and congener-differences in microcystin-LR and -RR GSH conjugation in human,rat, and mouse hepatic cytosol

The accepted pathway for MC biotransformation is GSH conjugation, occurring either spontaneously or catalyzed by GST. In the present work, the already available information on human MC metabolism have been expanded and the capacity of human GST to conjugate MC-LR has been confirmed in human liver cytosol. At physiological GSH content the spontaneous reaction predominated on the enzymatic one; the prevalence of the enzymatic reaction occurred following GSH depletion, and the shift was detectable at higher GSH levels, the lower was MC concentration. However, at low MC-LR concentrations (≤10 μM), representative of repeated oral exposure, the relevance of the enzymatic reaction became predominant at GSH concentration between 1 and 2 mM. MC-LR conjugate was detectable at ≥0.5 mM GSH, whereas, with 10 μM MC-RR detectable levels of conjugate were observed at 0.05 mM GSH, a 10-fold lower concentration. Overall, our data indicate that MC-RR is more efficiently conjugated than MC-LR, especially at low concentrations. Cytosol samples from rat and mouse were used to characterize GSH conjugation of MC-LR and MC-RR, and to check for possible species differences. At physiological GSH content, in both rodent species the enzymatic reaction accounted for half of the total conjugate formation, reducing the impact of spontaneous reaction with respect to human. Rat and mouse GST showed similar MC-LR and-RR GSH conjugation, but a two-fold higher catalytic efficiency than human sample. This is mainly due to higher affinity for the substrate, with K_mapp values being an order of magnitude lower in the animal models than in human liver cytosol. More pronounced differences in the metabolism of the two variants were evidenced in rodents than in humans.     

傍河取水工程对黄河水微囊藻毒素的去除效果

目的探讨傍河取水工程对黄河水中微囊藻毒素、藻细胞的去除效果,为该工程的推广应用和政府决策提供科学依据。方法现场水样采集后,低温保存运回实验室。细胞计数板法测定藻细胞密度,ELISA法测定微囊藻毒素。结果傍河取水工程对藻细胞和微囊藻毒素的去除率均在90.0%以上。结论傍河取水工程对藻细胞和微囊藻毒素有很好的去除效果。     

太湖流域水中微囊藻毒素含量调查

目的 了解有毒蓝藻水华频繁暴发的太湖流域周边城市水源水和饮用水中微囊藻毒素(MC)的含量.方法 采用50ng/L检出限的酶联免疫吸附试验,于2001年7月对江苏无锡10个调查点的水样MC含量进行测定.共收集水样90份,其中以太湖水或深井水为源水的7个自来水厂的水源厂、出厂水各11份,末梢水48份,浅井水17份,河水3份.结果 太湖水来源的8份水源水中均检出高浓度MC,其范围在2699～14188ng/L之间,源水处理后仍检出微量毒素(<100ng/L);深井源水、出厂水和末梢水均未检出毒素;浅井水MC检出率为29.4%,其浓度范围在64～323ng/L之间;仅1份河水检出MC.结论 采用常规饮水处理措施不足以完全去除水华时期水体中的MC,需进一步对该地区饮水MC污染危险性进行评价.