The role of microcystins in heavy cyanobacterial bloom formation

Regrettably, Figure 1 (part B) on p.695 was incorrect. The correctfigure appears below:     

Use of electrospray tandem mass spectrometry for identification of microcystins during a cyanobacterial bloom event

Drastic environmental conditions such as elevated temperature, abrupt pH variation, low turbulence, and high nutrient inputs can enhance the development of toxic cyanobacterial blooms in lakes and reservoirs. This study describes the occurrence of four microcystin variants (MC) in a bloom in the eutrophic reservoir Billings, in S?o Paulo City. The bloom sample was collected in October 2003, and Microcystis were the main genus found. The MC were separated and purified by reverse phase high performance liquid chromatography (RP-HPLC). Their structures were elucidated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and four MC variants were determined: MC-RR, MC-LR, MC-YR, and MC-hRhR. MC-hRhR is described for the first time as a new variant of MC with two homoarginines at positions 2 and 4 in its structure. ESI-MS/MS analysis thus provides a powerful and convenient tool for the determination of variants of MC. These results represent an important contribution to the knowledge of the biochemistry of toxic cyanobacteria and their toxins, specifically in S?o Paulo State.     

Towards clarification of the biological role of microcystins, a family of cyanobacterial toxins

Microcystins constitute a serious threat to the quality of drinking water worldwide. These protein phosphatase inhibitors are formed by various cyanobacterial species, including Microcystis sp. Microcystins are produced by a complex microcystin synthetase, composed of peptide synthetases and polyketide synthases, encoded by the mcyA-J gene cluster. Recent phylogenetic analysis suggested that the microcystin synthetase predated the metazoan lineage, thus dismissing the possibility that microcystins emerged as a means of defence against grazing, and their original biological role is not clear. We show that lysis of Microcystis cells, either mechanically or because of various stress conditions, induced massive accumulation of McyB and enhanced the production of microcystins in the remaining Microcystis cells. A rise in McyB content was also observed following exposure to microcystin or the protease inhibitors micropeptin and microginin, also produced by Microcystis. The extent of the stimulation by cell extract was strongly affected by the age of the treated Microcystis culture. Older cultures, or those recently diluted from stock cultures, hardly responded to the components in the cell extract. We propose that lysis of a fraction of the Microcystis population is sensed by the rest of the cells because of the release of non-ribosomal peptides. The remaining cells respond by raising their ability to produce microcystins thereby enhancing their fitness in their ecological niche, because of their toxicity.     

高温强太阳光照条件下蓝藻水华形成的实验研究

富营养化和藻类水华尤其是蓝藻水华在全世界范围内的湖泊中都有发生,但富营养化和水面藻类水华出现之间没有等同关系.目前人们对水华形成机制还不是很了解,对水华的具体形成过程也不是很清楚,因此若能通过一定的途径使没有形成水面水华的富营养水体出现水面水华就对水华形成机制的研究很有意义.实验选用高温季节里,于2007年8月28日将室外塑料蓝桶中培育的浮游植物丰富的天然水体-其中含有类颤藻鱼腥藻但其并不占据优势,引入到无色透明玻璃瓶中.实验初始水体的chl-a、TN和TP依次为 615.20mg·^-3、9.144mg·L^-1和0.453mg·L^-1.2007年8月29日对各处理进行营养盐的梯度添加,添加的营养盐为KNO₃和KH₂PO₄.共有4个营养盐添加梯度,添加的N/P(质量比)为7:1,其中添加的N的梯度为(mg·L-1):0,0.5,1.0和2.0.实验过程中测定了水温、光合有效辐射、氮磷营养盐、叶绿素a和浮游植物种类的数量变化.结果表明实验过程中各处理的营养盐和chl-a含量均比开始时有下降,同时各处理中水面出现了类颤藻鱼腥藻水华,且类颤藻鱼腥藻的数量随处理中营养盐添加量的增多而升高.这说明了含有少量鱼腥藻的高chl-a含量的天然水体在高温季节引入到透明玻璃容器中后能形成水表面鱼腥藻水华,玻璃容器中的高温强光照条件和营养盐的添加能促进鱼腥藻在竞争中取得优势.本实验利用小玻璃容器,排除了鱼类、风浪、底泥等多个因素的影响,集中关注营养盐添加和高温强光照因子,成功重现了蓝藻表面水华的发生.营养盐添加水平与浮游植物种间竞争并导致水体表面水华发生之间的关系在此实验中得到很好的体现.虽然本实验不能揭示蓝藻水华形成的具体机制,但为蓝藻水华形成机制研究提供了便捷的途径而很有意义.     

The role of interactions between Prorocentrum minimum and Heterosigma akashiwo in bloom formation

We examined the growth and interactions between the bloom-forming flagellates Prorocentrum minimum and Heterosigma akashiwo using bi-algal culture experiments. When both species were inoculated at high cell densities, growth of H. akashiwo was inhibited by P. minimum. In other combinations of inoculation densities, the species first reaching the stationary phase substantially suppressed maximum cell densities of the other species, but the growth inhibition effect of P. minimum was stronger than that of H. akashiwo. We used a mathematical model to simulate growth and interactions of P. minimum and H. akashiwo in bi-algal cultures. The model indicated that P. minimum always out-competed H. akashiwo over time. Additional experiments showed that crude extracts from P. minimum and H. akashiwo cultures did not affect the growth of either species, but both strongly inhibited the growth of the bloom-forming diatom Skeletonema costatum. Further experiments showed that it was unlikely that reactive oxygen species produced by H. akashiwo were responsible for the inhibition of P. minimum growth.     

A cyanobacterial bloom prevents fish trophic cascades

1. We experimentally compared the impacts of visually feeding zooplanktivorous fish and filter‐feeding omnivorous fish in shallow tropical Dakar Bango reservoir, Senegal. We provoked a cyanobacterial Anabaena bloom under mesotrophic to eutrophic N‐limited conditions in 18 enclosures assigned to six Nile tilapia life‐stage treatments, at typical biomasses: fishless control (C), zooplanktivorous fry (Z), omnivorous juveniles (O), herbivorous fingerlings (H) and two combinations (OZ, OH). 2. All fish grew well, but as prevalent inedible phytoplankton dampened fish effects, community‐level trophic cascades did not occur. Planktivore types acted independently and affected differentially the biomasses of total zooplankton, cyclopoids, nauplii, cladocerans, invertebrate carnivores, large herbivores, colonial cyanobacteria and Chlorophyta. They neither influenced the total biomass of phytoplankton, nor most water chemistry characteristics. Responses were apparently not fish‐biomass related. The bloom collapsed synchronously in all enclosures, coinciding with enrichment ending, with a return to clear water within 12 days. 3. Our results support the hypothesis that excess nutrients and prevalent inedible cyanobacteria inhibit the cascading effects of natural biomass levels of both visually feeding zooplanktivores and filter‐feeding omnivores. In N‐limited meso‐eutrophic shallow tropical lakes with predominantly small herbivorous zooplankton, neither the type nor the biomass of planktivorous fish present seems likely to prevent the transient outburst of cyanobacterial blooms. Such fragile ecosystems may thus not sustain a trophic state suitable for drinking water production, unless human impacts are restricted. The generality of restoration approaches based on ecological engineering should be further explored.     

Widespread distribution and identification of eight novel microcystins in antarctic cyanobacterial mats

The microcystin (MC) content and cyanobacterial community structure of Antarctic microbial mat samples collected from 40 ponds, lakes, and hydroterrestrial environments were investigated. Samples were collected from Bratina Island and four of the Dry Valleys, Wright, Victoria, Miers, and Marshall. Enzyme-linked immunosorbent assays (ELISAs), liquid chromatography-mass spectrometry (LC-MS), and protein phosphatase 2A (PP-2A) inhibition assays resulted in the identification of low levels (1 to 16 mg/kg [dry weight]) of MCs in all samples. A plot of indicative potencies of MCs (PP-2A inhibition assay/ELISA ratio) versus total MCs (ELISA) showed a general decrease in potency, as total MC levels increased, and a clustering of values from discrete geographic locations. LC-tandem MS analysis on selected samples identified eight novel MC congeners. The low-energy collisional activation spectra were consistent with variants of [D-Asp(3)] MC-RR and [D-Asp(3)] MC-LR containing glycine [Gly(1)] rather than alanine and combinations of homoarginine [hAr(2)] or acetyldemethyl 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid (acetyldemethyl ADDA) [ADMAdda(5)] substitutions. Nostoc sp. was identified as a MC producer using PCR amplification of a region of the 16S rRNA gene and the aminotransferase domain of the mcyE gene. Automated ribosomal intergenic spacer analysis (ARISA) was undertaken to enable a comparison of cyanobacterial mat community structure from distant geographical locations. Two-dimensional multidimensional scaling ordination analysis of the ARISA data showed that in general, samples from the same geographic location tended to cluster together. ARISA also enabled the putative identification of the MC-producing Nostoc sp. from multiple samples.     

气候变化与太湖蓝藻暴发的关系

对太湖区域40多年来气温、降水量、日照时数随时间变化的特征进行了分析,并对太湖蓝藻的爆发时间、次数、等级进行了统计,采用对比分析法对气候变化与太湖蓝藻暴发的关系进行了分析。结果表明:太湖区域1961—2007年总的气候倾向率,年平均气温为0.35℃.10a-1,年累计降水量为31.33mm.10a-1,年累计日照时数为-69.00h.10a-1;而突变点,气温在1989年,降水量在1979年,日照时数在1999年,在突变点年份后,气温升高、降水量增加和日照时数减少的趋势更加明显。2000—2007年气候变得异常,主要表现为气温上升速度加快,约为1961—2007年的3.7倍,5月和10月的这种气候倾向性更明显;降水量减少,比1961—2007年减少了178.10mm.10a-1,日照时数增加,比1961—2007年增加了244.23h.10a-1。气候变暖速度加快为太湖蓝藻的生长发育提供了热量条件;降水量减少,加速了太湖水质恶化,为蓝藻暴发提供了有利的水质环境条件;日照时数增多,充足的光照为蓝藻生长发育提供了优良的光合条件;温度偏高、降水量偏少、日照时数偏多的气候变化趋势对应太湖蓝藻暴发的次数也偏多,造成了太...     

卵孢金孢藻(Chrysosporum ovalisporum)——中国水华蓝藻新记录

卵孢金孢藻(Chrysosporum ovalisporum(Forti)Zapomelováet al.)是一种在欧洲地中海地区和澳大利亚较常见的水华蓝藻,但我国目前还未有该物种分布的报道。本文对采自上海市滴水湖中的藻种进行分离培养,获得了一株纯化藻株CFWA01007,经光学显微镜观察,初步判定其为卵孢金孢藻,对其形态特征进行了详细描述并测定了其16S rRNA基因序列,结果与来自欧洲和北美的Chrysosporum ovalisporum(Forti)Zapomelováet al.相似度极高,故判断其即为卵孢金孢藻,这是该种在中国的首次发现。对该种的分类学和生态学特征进行了讨论。     

Depth profiles of cyanobacterial hepatotoxins (microcystins) in three Turkish freshwater lakes

The Turkish freshwater lakes, Sapanca, Iznik and Taskisi (Calticak) have been enriched with nutrients from agriculture and domestic sources for many years. A major bloom of cyanobacteria (blue-green algae) in Lake Sapanca was recorded in May 1997, closely followed by a fish kill. Investigations were subsequently made on the cyanobacteria and water quality of the lakes, including analysis for cyanobacterial hepatotoxins (microcystins) in the filtered particulate fraction. Samples, taken from the beginning of May to end of August 1998, were analysed for microcystins by high–performance liquid chromatography with photodiode array detection (HPLC-PDA), protein phosphatase inhibition assay (PPIA) and an enzyme-linked immunosorbent assay (ELISA). No microcystins were detected in the water column in Lake Sapanca above 10 m, but toxins were found in filtered cyanobacterial samples from 20 m depth at a concentration of 3.65 μg l^?1 microcystin–LR equivalents. Ninety percent of the microcystin pool detected in L. Sapanca was found between depths of 15 and 25 m. The principal microcystin detected by HPLC-PDA was similar to microcystin–RR. Two unidentified microcystin variants were found in Lake Taskisi surface samples at a concentration of 2.43 μg l^?1 microcystin–LR equivalents in the filtered cyanobacterial cell fraction. Although 10 water samples (10 × 5 l) were taken from Lake Iznik (surface to 20 m, 5 m intervals), no microcystins were detected by HPLC-PDA (limit of detection 10 ng). The depth at which microcystins were detected in L. Sapanca coincided with the draw-off depth for the drinking water supply for the city of Sakarya     

Correction to: The role of vibronic modes in formation of red antenna states of cyanobacterial PSI

Photosynthesis Research - The funding statement in the first sentence of the Acknowledgements section in the original publication is incorrect. The corrected Acknowledgements section is printed below.     

含微囊藻毒素的蓝藻水华提取物对小鼠抗氧化酶的毒性作用

在世界范围内发生的富含营养的废水中生长蓝藻水华已经造成了严重的水污染。已有报道显示水华中的有毒成分是一类单环七肽微囊藻毒素,它们对人和家畜有严重的毒害作用,本文所使用的蓝藻水华采集于我国的太湖地区。我们采用三个亚致死计量(16、32、64 mg冻干藻细胞/kg体重,相当于4.97、9.94、19.88μg藻毒素/kg体重)的蓝藻水华提取物(CBE),分析它们对小鼠肝脏抗氧化酶的影响。经过连续14d每天腹腔注射CBE,小鼠分别在第3、5、7、9、11、13、15天处死并检测三种主要的抗氧化酶:超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽巯基转移酶(GST)的活性。SOD和CAT的活性均呈现了抑制效应,GST的活性也发生了明显的变化。为了进一步确定过氧化的程度,我们又通过检测丙二醛的含量分析了脂质过氧化的程度。经过14d CBE处理后脂质过氧化表现出了明显的浓度依赖性的上升趋势。我们的结果表明,CBE对小鼠的抗氧化酶有严重毒害作用,并且能够引起脂质的过氧化。     

Monitoring changing toxigenicity of a cyanobacterial bloom by molecular methods

Cyanobacterial blooms are potential health hazards in water supply reservoirs. This paper reports analyses of a cyanobacterial bloom by use of PCR-based methods for direct detection and identification of strains present and determination of their toxigenicity. Serial samples from Malpas Dam, in the New England region of Australia, were analyzed during a prolonged, mixed cyanobacterial bloom in the summer of 2000 to 2001. Malpas Dam has been shown in the past to have toxic blooms of Microcystis aeruginosa that have caused liver damage in the human population drinking from this water supply reservoir. Cyanobacterial genera were detected at low cell numbers by PCR amplification of the phycocyanin intergenic spacer region between the genes for the beta and alpha subunits. The potential for microcystin production was determined by PCR amplification of a gene in the microcystin biosynthesis pathway. The potential for saxitoxin production was determined by PCR amplification of a region of the 16S rRNA gene of Anabaena circinalis strains. Toxicity of samples was established by mouse bioassay and high-pressure liquid chromatography. We show that bloom components can be identified and monitored for toxigenicity by PCR more effectively than by other methods such as microscopy and mouse bioassay. We also show that toxigenic strains of Anabaena and Microcystis spp. occur at this site and that, over the course of the bloom, the cell types and toxicity changed. This work demonstrates that PCR detection of potential toxicity can enhance the management of a significant public health hazard.     

The role of microcystins in maintaining colonies of bloom-forming Microcystis spp

Microcystis is a cosmopolitan genus of cyanobacteria and occurs in many different forms. Large surface blooms of the cyanobacterium are well known in eutrophic lakes throughout the globe. We evaluated the role of microcystins (MCs) in promoting and maintaining bloom-forming cell aggregates at environmentally relevant MC concentrations (0.25-10 μg l(-1)). MCs significantly enhanced Microcystis colony sizes. Colonial diameters in microcystin-RR (MC-RR)-treated cultures (at 1 μg l(-1)) were significantly larger than control colonies, by factors of 1.5, 2.6 and 2.7 in Microcystis wesenbergii DC-M1, M. ichthyoblabe TH-M1 and Microcystis sp. FACHB1027 respectively. Depletion of extracellular MC concentrations caused Microcystis colony size to decrease, suggesting that released MCs are intimately involved in the maintenance of Microcystis colonial size. MC-RR exposure did not influence Microcystis growth rate, but did significantly increase the production of extracellular polysaccharides (EPS). In addition, MC-RR exposure appeared to trigger upregulation of certain parts of four polysaccharide biosynthesis-related genes: capD, csaB, tagH and epsL. These results strongly indicate that induction of polysaccharides by MC-RR was the major mechanism through which MCs enhanced colony formation in Microcystis spp. Cellular release of MCs, therefore, may play a key role in the persistence of algal colonies and the dominance of Microcystis.     

Photosynthesis and nitrogen fixation in a cyanobacterial bloom in the Baltic Sea

Daily integrals of photosynthesis by a cyanobacterial bloom in the Baltic Sea, during the summer of 1993, were calculated from the vertical distributions of light, temperature and the organisms in the water column and from photosynthesis/irradiance curves of picoplanktonic and diazotrophic cyanobacteria isolated from the community. The distribution of chlorophyll a in size-classes <20?µm and >20?µm was monitored over 9 days that included a deep mixing event followed by calm. Picocyanobacteria formed 70% of the cyanobacterial biomass and contributed 56% of the total primary production. Of the filamentous diazotrophs that formed the other 30%, Aphanizomenon contributed 28% and a Nodularia-containing fraction 16% of the primary production. For the whole population there was little change in standardized photosynthetic O₂ production, which remained at about 31?mmol?m^?2 before and after the mixing event. There were differences, however, between the classes of cyanobacteria: in picocyanobacteria primary production hardly changed, while in Aphanizomenon it increased by 2.6 and in Nodularia it fell below zero. Total phytoplankton photosynthesis was strongly dependent on total daily insolation with the compensation point at a photon insolation of 22.7?mol?m^?2?d^?1. Similar analyses of N₂ fixation showed much less dependence on depth distribution of light and biomass: Aphanizomenon fixed about twice as much N₂ as Nodularia their; their fixation exceeded their own N demand by about 12%. Together, these species contributed 49% of the total N demand of the phytoplankton population. Computer models based on the measured light attenuation and photosynthetic coefficients indicate that growth of the cyanobacterial population could occur only in the summer months when the critical depth of the cyanobacteria exceeds the depth of mixing.     

Optical changes associated with cyanobacterial bloom termination by viral lysis

Optical changes that accompanied a collapse of the populationof filamentous cyanobacteria from a shallow, eutrophic lakewere studied in laboratory-scale enclosures (LSEs). The experimentalconditions are known, from previous work on these systems, tocause a dramatic collapse of the dominant algal or cyanobacterialspecies, which in turn can be associated with viral activity.Within 2 weeks of continuous addition of nutrient-rich growthmedium, near-complete collapse of the dominant population occurredover the span of a few days. The collapse was repeatedly andreproducibly observed and was primarily characterized by a markedincrease in water transparency. Scattering of light decreasedby 80%, absorption decreased by 20–80%. There was highsimilarity in optical changes between several experiments, carriedout in different seasons. An increase of dissolved materialand submicron-sized particles (SMP) that showed chlorophylla (Chl a) absorption was observed during the collapse. The phycocyanin(PC): Chl a ratio and phaeopigment : Chl a ratio proved to begood indicators of the observed collapse. Reflectance spectrathat were modelled using a constant volume-scattering functionindicated that mass mortality of this magnitude can be detectedin natural systems using current remote sensors.     

Synergistic and species‐specific effects of climate change and water colour on cyanobacterial toxicity and bloom formation

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The possibility of using cyanobacterial bloom materials as a medium for white rot fungi

Aims: The present study was conducted to evaluate the possibility of using cyanobacterial bloom materials as a medium for white rot fungi and the capability of white rot fungi, Trichaptum abietinum 1302BG and Lopharia spadicea to biodegrade dried cyanobacterial bloom material taken from Taihu Lake. Methods and Results: The results showed T. abietinum 1302BG and L. spadicea could use the cyanobacterial bloom materials taken from Taihu Lake for growth to measure the mycelial plaque and dry‐weight mycelial pellicles of fungi. The removal rate of dried cyanobacterial bloom materials incubated with white rot fungi is approximately 100%. Conclusions: The cyanobacterial bloom material can be used as a glucose substitute in white rot fungi medium. The white rot fungi, T. abietinum 1302BG and L. spadicea, can also directly decrease the biomass of cyanobacterial bloom material taken from Taihu Lake. Significance and Impact of the Study: Cyanobacterial bloom thrives in eutrophic fresh waters all over the world. Micro‐organisms, particularly fungi, have attracted attention as possible agents for the degradation of phytoplankton species. Dealing with cyanobacterial bloom material as a medium for fungi instead of directly discharging them as organic fertilizers is a new, safe and environmentally friendly approach.