Cyanobacteria Microcystis aeruginosa Contributes to the Severity of Fish Diseases: A Study on Spring Viraemia of Carp

Fish are exposed to numerous stressors in the environment including pollution, bacterial and viral agents, and toxic substances. Our study with common carps leveraged an integrated approach (i.e., histology, biochemical and hematological measurements, and analytical chemistry) to understand how cyanobacteria interfere with the impact of a model viral agent, Carp sprivivirus (SVCV), on fish. In addition to the specific effects of a single stressor (SVCV or cyanobacteria), the combination of both stressors worsens markers related to the immune system and liver health. Solely combined exposure resulted in the rise in the production of immunoglobulins, changes in glucose and cholesterol levels, and an elevated marker of impaired liver, alanine aminotransferase (ALT). Analytical determination of the cyanobacterial toxin microcystin-LR (MC-LR) and its structurally similar congener MC-RR and their conjugates showed that SVCV affects neither the levels of MC in the liver nor the detoxification capacity of the liver. MC-LR and MC-RR were depurated from liver mostly in the form of cysteine conjugates (MC-LR-Cys, MC-RR-Cys) in comparison to glutathione conjugates (LR-GSH, RR-GSH). Our study brought new evidence that cyanobacteria worsen the effect of viral agents. Such inclusion of multiple stressor concept helps us to understand how and to what extent the relevant environmental stressors co-influence the health of the fish population.     

福建省部分水源微囊藻毒素污染调查

目的 报告福建省部分饮用水水源微囊藻毒素污染状况调查结果,探讨饮用水水源微囊藻毒素的危害及预防措施.方法 1998,2000年在厦门同安肝癌高发区抽样采集浅井水49份、自来水4份、水库水3份,竞争酶联免疫吸附法（ELISA）测定水样中微囊藻毒素;2001年8-9月份采集福州山仔水库微囊藻水华,小鼠生物法测定微囊藻水华急性毒性,高效液相色谱法定性、定量测定微囊藻毒素类型和含量.结果 厦门同安农村饮用水水源普遍存在微囊藻毒素污染,夏季藻类生长高峰期,水库水微囊藻毒素检出率100%,浅井水检出率77.5%;同安水源中优势藻为颤藻,其次为微囊藻.福州山仔水库微囊藻水华LD50为9.9 g藻浆/kg,平均死亡时间2.5 h.每克鲜藻浆含微囊藻毒素20.5μg,主要毒素类型为MC-RR,其次为MC-LR和MC-YR.结论 福建省部分饮用水水源存在微囊藻毒素污染,山仔水库微囊藻毒素主要类型为MC-RR,有明显的肝毒性.     

太湖地区城市饮用水微囊藻毒素与恶性肿瘤死亡率的关系

目的:研究饮用水微囊藻毒素(MC)与恶性肿瘤死亡率的关系。方法:在江苏无锡选取10个饮水类型不同的乡镇或街道作为调查点开展一项生态流行病学研究。收集1992-2000年各调查点恶性肿瘤的死亡资料,同时采集不同类型水样,综合评价各调查点MC的暴露水平。分析MC暴露等级与恶性肿瘤死亡率的相关关系。结果:饮用水MC暴露等级与男性胃癌和男性各部位合计恶性肿瘤的直接和间接标化死亡率呈现正相关;与男性肠癌的直接标化死亡率呈现负相关(P<0.05);未发现MC与女性恶性肿瘤标化死亡率、人群截缩标化死亡率之间存在相关(P>0.05)。结论:饮水MC污染可能与无锡地区男性恶性肿瘤死亡率,尤其是胃癌死亡率的上升有关。     

Co-production of microcystins and aeruginopeptins by natural cyanobacterial bloom

The relationship between Microcystis composition and the production of microcystins and nontoxic peptides in bloom cells, which was regularly collected in Lake Suwa, Japan, in the summer season from 1991 to 1994, was investigated. In order to determine the structures of the nontoxic peptides, we collected large amounts of bloom materials from the same lake on July 23, 1991, and isolated three nontoxic peptides. They were named as aeruginopeptins 917S-A, -B, and -C, and their structures were mainly determined by a mass spectrometry/mass spectrometry (MS/MS) technique as 19-membered cyclic depsipeptides possessing the Ahp (3-amino-6-hydroxy-2-piperidone) moiety. An analysis of the microcystins and aeruginopeptins in the collected blood cells and their Microcystis composition suggested that the M. aeruginosa large cell size produces both microcystins and aeruginopeptins, and the production of both compounds is genetically closely related.     

Insight into the Molecular Mechanism for the Discrepant Inhibition of Microcystins (MCLR,LA, LF,LW, LY) on Protein Phosphatase 2A

Microcystins (MCs) exhibit diversified inhibition effects on protein phosphatases (PPs) due to their structural differences. To fully evaluate the potential mechanism for the discrepant inhibition effects, the five most frequent MCs with varying residues at position Z⁴ were selected as the tested toxins. Their inhibition sequence on PP2A was detected as follows: MCLR > MCLW > MCLA > MCLF > MCLY. Combined with homology modeling and molecular docking technology, the major interaction parameters between the MCs and PP2A were obtained. The correlation analysis for the major interaction parameters and inhibition effects showed that the hydrophobicity of Z⁴ had an important influence on the interaction of the MCs to PP2A. The introduction of hydrophobic Z⁴ directly weakened hydrogen bonds Z⁴→Pro₂₁₃ and Z⁴←Arg₂₁₄, indirectly weakened hydrogen bonds Adda⁵←Asn₁₁₇, Glu⁶←Arg₈₉, and MeAsp³←Arg₈₉, but indirectly enhanced ionic bonds Glu⁶←Arg₈₉, Glu⁶-Mn₁²⁺, and Glu⁶-Mn₂²⁺. In this way, the combination of the MCs with PP2A was blocked, and thus, the interactions between PP2A and the Mn²⁺ ions (in the catalytic center) were further affected; metal bonds Asp₈₅-Mn₁²⁺ and Asp₈₅-Mn₂²⁺ were weakened, while metal bond His₂₄₁-Mn₁²⁺ was enhanced. As a result, the interactions in the catalytic center were inhibited to varying degrees, resulting in the reduced toxicity of MCs.     

微囊藻毒素LR诱导无DNA片断化的细胞凋亡

目的研究微囊藻毒素(microcystin,MC)损伤肝细胞的毒性机制。方法以不同浓度的微囊藻毒素LR(MCLR)处理L-02肝细胞,通过光镜和电镜下的形态观察、DNA片断化分析、线粒体膜电位变化等了解MCLR对肝细胞的毒性效应。结果光镜下观察表明,50!g/mlMCLR处理可使细胞变圆、萎缩、不贴壁生长,电镜下L-02细胞呈现皱缩、膜发泡及染色质凝聚并边缘化等变化,这是典型的细胞凋亡形态特征,但电镜下没有观察到凋亡小体的形成;DNA电泳表明凋亡细胞没有出现明显的DNAladder,与电镜观察的结果一致。流式细胞仪检测发现以50!g/mlMCLR处理60h后,细胞的线粒体膜电位显著下降。结论微囊藻毒素损伤线粒体可能是其损伤细胞的途径之一,这种微囊藻毒素诱导的无DNA片段断裂的凋亡现象属首次报道,具体机制有待进一步阐明。     

The Importance of Lake Sediments as a Pathway for Microcystin Dynamics in Shallow Eutrophic Lakes

Microcystins are toxins produced by cyanobacteria. They occur in aquatic systems across the world and their occurrence is expected to increase in frequency and magnitude. As microcystins are hazardous to humans and animals, it is essential to understand their fate in aquatic systems in order to control health risks. While the occurrence of microcystins in sediments has been widely reported, the factors influencing their occurrence, variability, and spatial distribution are not yet well understood. Especially in shallow lakes, which often develop large cyanobacterial blooms, the spatial variability of toxins in the sediments is a complex interplay between the spatial distribution of toxin producing cyanobacteria, local biological, physical and chemical processes, and the re-distribution of toxins in sediments through wind mixing. In this study, microcystin occurrence in lake sediment, and their relationship with biological and physicochemical variables were investigated in a shallow, eutrophic lake over five months. We found no significant difference in cyanobacterial biomass, temperature, pH, and salinity between the surface water and the water directly overlying the sediment (hereafter ‘overlying water’), indicating that the water column was well mixed. Microcystins were detected in all sediment samples, with concentrations ranging from 0.06 to 0.78 µg equivalent microcystin-LR/g sediments (dry mass). Microcystin concentration and cyanobacterial biomass in the sediment was different between sites in three out of five months, indicating that the spatial distribution was a complex interaction between local and mixing processes. A combination of total microcystins in the water, depth integrated cyanobacterial biomass in the water, cyanobacterial biomass in the sediment, and pH explained only 21.1% of the spatial variability of microcystins in the sediments. A more in-depth analysis that included variables representative of processes on smaller vertical or local scales, such as cyanobacterial biomass in the different layers and the two fractions of microcystins, increased the explained variability to 51.7%. This highlights that even in a well-mixed lake, local processes are important drivers of toxin variability. The present study emphasises the role of the interaction between water and sediments in the distribution of microcystins in aquatic systems as an important pathway which deserves further consideration.     

Integrative Monitoring of Marine and Freshwater Harmful Algae in Washington State for Public Health Protection

The more frequent occurrence of both marine and freshwater toxic algal blooms and recent problems with new toxic events have increased the risk for illness and negatively impacted sustainable public access to safe shellfish and recreational waters in Washington State. Marine toxins that affect safe shellfish harvest in the state are the saxitoxins that cause paralytic shellfish poisoning (PSP), domoic acid that causes amnesic shellfish poisoning (ASP) and the first ever US closure in 2011 due to diarrhetic shellfish toxins that cause diarrhetic shellfish poisoning (DSP). Likewise, the freshwater toxins microcystins, anatoxin-a, cylindrospermopsins, and saxitoxins have been measured in state lakes, although cylindrospermopsins have not yet been measured above state regulatory guidance levels. This increased incidence of harmful algal blooms (HABs) has necessitated the partnering of state regulatory programs with citizen and user-fee sponsored monitoring efforts such as SoundToxins, the Olympic Region Harmful Algal Bloom (ORHAB) partnership and the state’s freshwater harmful algal bloom passive (opportunistic) surveillance program that allow citizens to share their observations with scientists. Through such integrated programs that provide an effective interface between formalized state and federal programs and observations by the general public, county staff and trained citizen volunteers, the best possible early warning systems can be instituted for surveillance of known HABs, as well as for the reporting and diagnosis of unusual events that may impact the future health of oceans, lakes, wildlife, and humans.     

我国水环境微囊藻毒素污染及其健康危害研究

随着我国水体污染逐渐加重,出现富营养化而导致的蓝藻水华日趋普遍,微囊藻毒素(Microcystin,MC)污染已成为亟待关注的环境问题.本文中概述了近年来我国水环境和生物体内MC污染状况、毒效应以及人群流行病学调查等方面的研究进展.