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首页> 外文期刊>Harmful Algae >Seasonal patterns of microcystin-producing and non-producing Planktothrix rubescens genotypes in a deep pre-alpine lake
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Seasonal patterns of microcystin-producing and non-producing Planktothrix rubescens genotypes in a deep pre-alpine lake

机译：高山前深湖中微囊藻毒素生产和非生产藻红藻基因型的季节性模式

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The filamentous cyanobacterium Planktothrix rubescens produces secondary metabolites called microcystins (MC) that are potent toxins for most eukaryotes, including zooplankton grazers, cattle and humans. P. rubescens occurs in many deep and thermally stratified lakes throughout Europe. In Lake Zurich (Switzerland), it re-appeared in the 1970s concomitant with decreasing eutrophication. Since then, P. rubescens has become the dominant species in this major drinking water reservoir, where it forms massive metalimnetic blooms during late summer. These cyanobacteria harbor subpopulations of non-MC producers, but little is known about the environmental factors affecting the success of such genotypes. The non-MC-producing subpopulation of P. rubescens was studied using a quantitative real-time PCR (qPCR) assay on the MC synthetase (mcy) gene cluster that targets a deletion on the mcyH and mcyA genes, which inactivates MC biosynthesis. Two complementary qPCR assays were used to assess the total population abundance (based on the 16S rDNA gene) and the mcy gene copy number (based on a conserved region in the adenylation domain of the mcyB gene). The objective was to evaluate the seasonal patterns of the share of non-MC-producing filaments in the total P. rubescens population. The mcyHA mutants were present in low proportions (up to 14%) throughout the year. Their highest relative abundances occurred during the winter mixis, when total concentrations of P. rubescens were minimal. The MC deficient mutants seemed to better survive in sparse populations, possibly because of lower grazing pressure and a consequently reduced need for MG-mediated protection. Alternatively, the mutants might cope better with the sub-optimal, stressful pressure and light conditions during the winter mixis. Altogether, our results suggest that subtle trade-offs might seasonally determine the proportions of non-MC producers within P. rubescens populations. (C) 2015 Elsevier B.V. All rights reserved.
机译：丝状蓝藻浮游生物产生称为微囊藻毒素（MC）的次级代谢产物，是大多数真核生物（包括浮游动物放牧者，牛和人）的有效毒素。风疹在整个欧洲的许多深层和热分层湖泊中都有发生。在苏黎世湖（瑞士）中，随着富营养化程度的降低，它在1970年代再次出现。从那以后，红景天已成为这个主要饮用水水库中的主要物种，在夏末形成大量的金属花开。这些蓝细菌包含非MC生产者的亚群，但对影响此类基因型成功的环境因素知之甚少。使用定量实时PCR（qPCR）分析法对MC合成酶（mcy）基因簇进行了研究，研究了风疹假单胞菌的非MC亚群，该基因簇靶向mcyH和mcyA基因的缺失，从而使MC生物合成失活。两种互补的qPCR分析用于评估总群体丰度（基于16S rDNA基因）和mcy基因拷贝数（基于mcyB基因的腺苷酸化结构域中的保守区域）。目的是评估不生产MC的细丝在冬凌草总种群中所占份额的季节性模式。全年中，mcyHA突变体的比例很低（最高14％）。它们的最高相对丰度发生在冬季混交林中，当时风铃草的总浓度极低。缺乏MC的突变体似乎在稀疏种群中更好地生存，这可能是由于较低的放牧压力并因此减少了对MG介导的保护的需求。另外，突变体可能更好地应对冬季混血期的次优，压力和光照条件。总的来说，我们的结果表明，微妙的权衡可能会季节性决定红景天种群中非MC生产者的比例。 （C）2015 Elsevier B.V.保留所有权利。

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