环境水体微囊藻毒素微生物降解技术研究进展

湖库水体富营养化及其产生的藻毒素污染已对生态环境和人类健康构成极大威胁,而目前常规水污染控制技术存在一定的局限性,因此水环境中藻毒素处理新工艺亟待研发.鉴于环境水体中的微囊藻毒素可被微生物降解为无毒或低毒的中间产物,本文综述了微囊藻毒素的降解菌株、生物降解过程影响因素与机理、降解产物及其结构特性等,总结了目前微囊藻毒素降解菌株在水环境修复中的应用,并对今后微生物降解微囊藻毒素的研究方向进行了展望,以期为解决我国日益严峻的湖库水体藻毒素污染和饮用水安全问题提供技术思路.     

微囊藻毒素对鱼类的毒性效应

湖泊富营养化导致的蓝藻水华已成为国内外普遍关注的环境问题,它所带来的主要危害之一是产生的藻毒素对鱼类的影响。在已发现的藻毒素中,微囊藻毒素(microcystins,MCs)的分布广、毒性大、危害严重,而备受关注。阐述了MCs对鱼类的影响。微囊藻毒素能干扰胚胎的发育,降低孵化率,增加畸形率,影响存活率,胚胎孵化受微囊藻毒素影响还具有剂量依赖效应;野外室内实验均表明鱼类暴露于微囊藻毒素后不仅可在肝脏中富集还可在肌肉、肠道等组织器官中快速积累;对鱼类进行组织病理检测发现MCs可导致肝脏、肾脏、心脏、脑、鳃等组织受损;MCs在鱼体中的解毒过程可能开始于由谷胱甘肽S-转移酶催化的还原型谷胱甘肽的结合反应;MCs还可影响鱼类的生长、行为和血清生化指标,此外,还具有一定的免疫毒性。MCs的转运机制和分子作用机制以及在食物链中传递过程中对人类造成的潜在影响可能成为今后研究重点。     

微囊藻毒素对水环境的影响研究进展

微囊藻毒素是富营养化淡水水体中最常见的藻类毒素,是湖泊蓝藻产生的一类肽类毒素,它的产生受到藻类的遗传和环境因素的共同影响。由于其毒性大,分布广,结构稳定,从而成为水环境中的潜在危害物质。有关微囊藻毒素性质、毒理毒性、在环境中的迁移、转化以及控制预防已成为关注热点。在总结国内外研究的基础上,综述了微囊藻毒素的性质、产生机理以及其与水环境、水生生物(水生植物、鱼类、无脊椎动物)间的相互作用,讨论了微囊藻毒素对水生生物的影响以及水生生物对微囊藻毒素的降解作用,为水体中微囊藻毒素的防治提供科学的依据。     

微囊藻毒素生物治理技术研究进展*

近年来,随着全球气候变暖和水体富营养化程度加深,蓝藻水华频繁暴发。微囊藻毒素是有害蓝藻产生及释放的危害最大的一类蓝藻毒素,对生态环境和公众健康造成了严重的威胁。因此,寻求有效的微囊藻毒素降解方法已成为全球科学领域的研究热点。针对微囊藻毒素生物治理技术展开综述,阐述了微囊藻毒素的产生、理化性质及生物毒性,总结了微生物、水生植物、浮游动物等自然生物降解微囊藻毒素的能力。在此基础上概述了生物滤池、人工湿地、生态浮床、膜生物膜反应器等生物治理技术对微囊藻毒素的去除效果,分析了现有微囊藻毒素生物处理方法的优势和局限性,并对今后的研究方向提出展望,为解决水环境中微囊藻毒素的污染问题提供思路。     

水生态系统中微囊藻毒素的分布及其生态毒理效应研究进展

有毒蓝藻产生的蓝藻毒素对淡水生态系统构成了严重的全球性环境威胁,其中微囊藻毒素(MCs)是所有蓝藻毒素中分布最广、危害最大的一类肝毒素。MCs已对水生态系统的结构、功能和稳定性造成了不良影响,并对人类健康构成威胁。本文综述了当前MCs在水体、沉积物和水生动物体内的分布,以及MCs的生物毒性机制,在此基础上,总结了MCs对水生动物、水生植物及陆生植物的生态毒理效应,及其引发的人类健康风险,并关注了MCs的生物防治方法。最后,针对当前MCs相关研究领域中存在的不足提出展望,旨在为淡水水体中MCs的风险评估与治理管控提供参考。     

微囊藻与水体细菌相互关系的研究进展

近年来, 微生物群落在水生态系统中的结构和功能受到了越来越多的关注。在富营养化水体中细菌在微囊藻水华的发生、发展及衰亡、降解过程中发挥着重要的作用。文章总结了水体中微囊藻与细菌独有的群落结构特征,以及微囊藻与细菌群落对环境因素变化的响应等方面的研究成果。在微囊藻与细菌的相互作用方面, 从藻细胞微环境中附着细菌对微囊藻生长的促进或抑制作用, 细菌在微囊藻群体的形成和维持过程的作用, 细菌参与的微囊藻水华的聚集和降解过程, 细菌对微囊藻毒素的降解作用等方面进行了综述。文章还对未来微囊藻与细菌相互关系的研究热点以及可利用的组学技术等进行了展望。     

微囊藻毒素对陆生植物的污染途径及累积研究进展

微囊藻毒素(Microcystins,MCs)是全世界范围内普遍存在、且随着水体污染的加剧而在自然环境中大量积聚的蓝藻毒素之一,对多种生物有着严重的毒性作用.MCs在生物体内富集并通过食物链传递,对人类健康造成威胁.近些年,MCs对陆生植物的毒害作用及累积研究尤为引人关注,取得了一批重要的研究成果.MC-LR(L为亮氨酸)和MC-RR(R为精氨酸)是淡水水体中普遍存在且危害较大的两种MCs异构体.针对这两种毒素,重点介绍其对陆生植物的污染途径、毒性作用及其在作物体内的累积量,对今后的研究进行了展望.     

蓝藻毒素去除方法研究进展

蓝藻水华中产生的次生代谢产物蓝藻毒素对人类及陆生动物具有严重毒性和致癌作用,同时会危害水域生态系统的结构和功能。有毒藻华的频繁发生及其引发的环境和健康问题已经成为全球环境科学领域的研究热点。现有的净水技术去除饮用水中藻毒素效率不高,因此寻找高效的藻毒素去除方法是目前亟待解决的问题。本文首先阐述了蓝藻毒素的产生和释放机理,将蓝藻毒素的去除分为除藻和去除水体中溶解性藻毒素两类;其次,本文在国内外大量研究成果的基础上综述了当前蓝藻毒素的降解途径,并详细介绍了活性炭吸附法、高级氧化降解法、微生物降解法等具有实际应用前景的去除方法;最后,本文总结了当前蓝藻毒素去除方法的局限性,指出了未来的研究应向高效率、低能耗、无污染、实用性强的方向发展。     

微囊藻毒素降解菌的筛选、鉴定及其降解活性研究

采用从巢湖水华蓝藻细胞中提取、提纯的藻毒素（Microcystins,MCs）为微生物生长的唯一碳源和氮源,通过平板分离纯化,从巢湖底泥中分离出5株能够降解藻毒素的菌株,并对其中降解活性较高的一株进行分子鉴定。应用PCR技术克隆到16S rDNA片段,核苷酸序列分析结果表明,该菌的16S rDNA的全序列与吉氏库特菌kurthia gib-soniistrain HC050630C-1的相似性达99%。微囊藻毒素降解实验结果表明,用15mg/L乙醇作为外加碳源时可显著提高菌株M9降解MCs的能力,在48h内对初始浓度分别为17.1mg/L的MC-RR和11.3mg/L的MC-LR的降解率分别达到70.0%和81.6%。而葡萄糖对菌株M9的生长有明显抑制作用。     

微囊藻毒素生物合成基因及其功能研究进展

水体富营养化加剧,导致了蓝藻水华在世界范围内频发。蓝藻产生的微囊藻毒素是最常见的一种藻毒素,对人类和动物造成了很大的危害甚至导致死亡。微囊藻毒素经非核糖体合成途径由多肽合成酶合成。对微囊藻毒素的结构与性质、微囊藻毒素合成基因的功能及其生物合成、微囊藻毒素的分子生物学检测技术进行了评述,对未来的研究方向进行了展望。     

Turbulence increases the risk of microcystin exposure in a eutrophic lake (Lake Taihu) during cyanobacterial bloom periods

Toxic cyanobacterial harmful algal blooms (CyanoHABs) have posed serious water use and public health threats because of the toxins they produce, such as the microcystins (MCs). The direct physical effects of turbulence on MCs, however, have not yet been addressed and is still poorly elucidated. In this study, a 6-day mesocosm experiment was carried out to evaluate the effects of wind wave turbulence on the competition of toxic Microcystis and MCs production in highly eutrophicated and turbulent Lake Taihu, China. Under turbulent conditions, MCs concentrations (both total and extracellular) significantly increased and reached a maximum level 3.4 times higher than in calm water. Specifically, short term (∼3 days) turbulence favored the growth of toxic Microcystis species, allowing for the accumulation of biomass which also triggered the increase in MCs toxicity. Moreover, intense turbulence raises the shear stress and could cause cell mechanical damage or cellular lysis resulting in cell breakage and leakage of intracellular materials including the toxins. The results indicate that short term (∼3 days) turbulence is beneficial for MCs production and release, which increase the potential exposure of aquatic organisms and humans. This study suggests that the importance of water turbulence in the competition of toxic Microcystis and MCs production, and provides new perspectives for control of toxin in CyanoHABs-infested lakes.     

A review of microcystin detections in Estuarine and Marine waters: Environmental implications and human health risk

Toxin production by harmful cyanobacteria blooms (CyanoHABs) constitutes a major, worldwide environmental threat to freshwater aquatic resources that is expected to expand in scale and intensity with global climate change. Extensive literature exists on the most frequently encountered cyanotoxin, microcystin, in freshwater environments. Yet, the expansion of microcystin producing CyanoHABs and the transport of contaminated inland waters to estuarine and coastal marine waters has only recently received attention. This paper synthesizes information on the salinity tolerance of microcystin producing cyanobacteria and summarizes available case reports on microcystin presence in estuarine and coastal waters. We highlight a potential food-borne exposure route to humans by reviewing the growing body of evidence that shows microcystins can accumulate in coastal seafood. These cases reinforce the importance of freshwater nutrient reduction and the need for freshwater management efforts to look beyond lacustrine and riverine systems. Events reviewed here likely only represent a small proportion of cases where microcystins affect estuarine and coastal waters. We strongly suggest increased monitoring and research efforts to understand, react to, and prevent ecological and health problems associated with the growing problem of toxic CyanoHABs in coastal environments.     

A review on factors affecting microcystins production by algae in aquatic environments

Microcystins, a toxin produced by Microcystis aeruginosa have become a global environmental issue in recent years. As a consequence of eutrophication, microcystins have become widely disseminated in drinking water sources, seriously impairing drinking water quality. This review focuses on the relationship between microcystins synthesis and physical, chemical, and biological environmental factors that are significant in controlling their production. Light intensity and temperature are the more important physical factors, and in many cases, an optimum level for these two factors has been observed. Nitrogen and phosphorus are the key chemical factors causing frequent occurrence of harmful algal blooms and microcystins production. The absorption of nutrients and metabolic activities of algae are affected by different concentrations and forms of nitrogen and phosphorus, leading to variations in microcystins production Metal ions and emerging pollutants are other significant chemical factors, whose comprehensive impact is still being studied. Algae can also interact with biological agents like predators and competitors in aquatic environments, and such interactions are suggested to promote MCs production and release. This review further highlights areas that require further research in order to gain a better understanding of microcystins production. It provides a theoretical basis for the control of microcystins production and releasing into aquatic environments.     

In vivo studies on the toxic effects of microcystins on mitochondrial electron transport chain and ion regulation in liver and heart of rabbit

This study examined the toxic effects of microcystins on mitochondria of liver and heart of rabbit in vivo. Rabbits were injected i.p. with extracted microcystins (mainly MC-RR and -LR) at two doses, 12.5 and 50 MC-LReq. microg/kg bw, and the changes in mitochondria of liver and heart were studied at 1, 3, 12, 24 and 48 h after injection. MCs induced damage of mitochondrial morphology and lipid peroxidation in both liver and heart. MCs influenced respiratory activity through inhibiting NADH dehydrogenase and enhancing succinate dehydrogenase (SDH). MCs altered Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities of mitochondria and consequently disrupted ionic homeostasis, which might be partly responsible for the loss of mitochondrial membrane potential (MMP). MCs were highly toxic to mitochondria with more serious damage in liver than in heart. Damage of mitochondria showed reduction at 48 h in the low dose group, suggesting that the low dose of MCs might have stimulated a compensatory response in the rabbits.     

Investigation and assessment of environmental pollution in Gonghu Bay,Taihu Lake,China: A year-long study

Abstract

To understand environmental pollution and assess water quality in Gonghu Bay of Taihu Lake, the eutrophication status and microcystins (MCs) occurrence were monitored monthly from December 2015 to November 2016. Moreover, the pollution of metals and antibiotics was investigated and assessed. In May 2016, the comprehensive trophic level index (∑TLI) at most sampling sites in Gonghu Bay were hypereutrophic, demonstrating that the eutrophication status in Gonghu Bay is still quite intense. The persistent and ubiquitous occurrence of MCs was observed in the water of Gonghu Bay throughout the monitoring period. Moreover, various metal elements and antibiotic compounds were found in the surface water of Gonghu Bay, in which arsenic (As) and sulfamethoxazole (SMX) respectively showed high risks. Overall, the water quality of eastern Gonghu Bay is affected mainly by eutrophication, while the antibiotic pollution level is higher in the southern part of Gonghu Bay. Continuous and long-term monitoring efforts are required to document the tendency of water quality change in Gonghu Bay and other parts of Taihu Lake to improve environmental management works.     

A graphene oxide based biosensor for microcystins detection by fluorescence resonance energy transfer

Water safety is one of the most pervasive problems afflicting people throughout the world. Microcystin, a hepatotoxin produced by cyanobacteria, poses a growing and serious threat of water safety. According to World Health Organization (WHO), the limit of content of microcystin-LR (MC-LR) in drinking water is as low as 1μg/L; it is thus necessary to explore a sensitive method for the trace detection of microcystins (MCs). Based on the observation of gold nanoparticles (Au NPs) induced graphene oxide (GO) fluorescence quenching, a reliable biosensor was developed here for microcystins detection. MCs could be attached on Au NPs through the interaction with single strand-DNA (ss-DNA) modified on Au NPs, which formed Au-DNA-MCs complexes. These MCs in the complexes could be immunologically recognized by the antibodies adsorbed on GO sheets, as a result, Au NPs were close enough to quench the photoluminescence of GO by the fluorescence resonance energy transfer (FRET). The fluorescence intensity decreased with the increase of MCs as more Au NPs linked onto GO surface. The limit of detection was 0.5 and 0.3μg/L for microcystin-LR and microcystin-RR (MC-RR), respectively, which satisfies the strictest standard of WHO. Well defined results were also obtained in natural lake water and the specificity experiment. The antibody used here could recognize Adda group, the conservative part of MCs, which allowed the biosensor to detect both single toxin and the total content of MCs existing in the water sample.     

Biodegradation of Microcystins during Gravity-Driven Membrane (GDM) Ultrafiltration

Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L⁻¹ MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified.     

The cyanotoxin-microcystins: current overview

The monocyclic heptapeptides microcystins (MCs), are a group of hepatotoxins, produced worldwide by some bloom-forming cyanobacterial species/strains both in marine and freshwater ecosystems. MCs are synthesized non-ribosomally by large multi-enzyme complexes consisting of different modules including polyketide synthases and non-ribosomal peptide synthetases, as well as several tailoring enzymes. More than 85 different variants of MCs have been reported to exist in nature. These are chemically stable, but undergo bio-degradation in natural water reservoirs. Direct or indirect intake of MCs through the food web is assumed to be a highly exposed route in risk assessment of cyanotoxins. MCs are the most commonly found cyanobacterial toxins that cause a major challenge for the production of safe drinking water and pose a serious threat to global public health as well as fundamental ecological processes due to their potential carcinogenicity. Here, we emphasize recent updates on different modes of action of their possible carcinogenicity. Besides the harmful effects on human and animals, MC producing cyanobacteria can also present a harmful effect on growth and development of agriculturally important plants. Overall, this review emphasizes the current understanding of MCs with their occurrence, geographical distribution, accumulation in the aquatic as well as terrestrial ecosystems, biosynthesis, climate-driven changes in their synthesis, stability and current aspects on its degradation, analysis, mode of action and their ecotoxicological effects.     

样品制备过程对测定水中溶解态微囊藻毒素的影响

系统比较了5种不同材质滤膜对于制备溶解态微囊藻毒素的影响,发现了影响藻毒素测定样品前处理的关键操作步骤。结果表明,醋酸纤维滤膜（CA filter）最多可吸附样品中79%的藻毒素,导致测得的MCs浓度严重偏低。玻璃纤维（GF/C）滤膜和聚醚砜（PES）材质滤器对制备溶解态微囊藻毒素过程影响很小。另外,发现离心法无法完全去除野外水华样品中藻细胞,反而可能导致藻细胞破裂,释放藻毒素,影响水中溶解态微囊藻毒素的测定。研究结果将对发展水体中溶解态藻毒素测定标准方法提供依据。