Water bloom-forming cyanobacteria have a severe impact on freshwater quality. Although some cyanobacterial toxins such as microcystins have been studied extensively, other toxins like anatoxin-a (ATX) and their structural analogs - as well as cyanobacterial taxa producing these toxins remain to be explored in detail. The present study investigated levels of ATX, CYN and their homologs along with the occurrence of anaC and cyrJ genes in water blooms in 16 sites in the Czech Republic that were pre-selected concerning the presence of potential toxin producers. Besides, we also studied toxins and genes in a series of strains available in our laboratories. ATX and its congener HATX were detected in 5 natural biomass samples from the Czech Republic (maximum concentration 2.8 micrograms per gram d.w.). Interestingly, the anaC gene coding for ATX production was not detected in any of these toxin-positive biomass samples. The concentrations of ATX congeners in cyanobacterial laboratory strains were about 10-times higher than those of the original ATX, which calls for further research addressing levels and hazards of ATX analogs. Regarding the CYN and 7-deoxyCYN (other CYN congeners were not analyzed in this study) - these toxins were identified in a single small pond in the Czech Republic at concentrations 4.3 and 2.7 micrograms per gram of biomass d.w., respectively (corresponded to dissolved concentrations higher than 1 microgram per liter). The CYN-positive sample was dominated by CYN-producing taxa Raphidiopsis (basionym Cylindrospermopsis) and Cuspidothrix. We also confirmed the presence of a specific cyrJ gene in this natural bloom sample. To our knowledge, this is the first study pointing to Raphidiopsis (Cylindrospermopsis) and Cuspidothrix as producers of CYN in Europe. This observation calls for further research because of their increasing occurrence in (Central) Europe along with the global change. The present study demonstrates the importance of using combined (taxonomical, analytical, and molecular) approaches in the assessment of hazardous cyanobacteria and their toxins in freshwaters.

形成水华的蓝藻对淡水质量有严重影响。尽管已经对一些蓝藻毒素（例如微囊藻毒素）进行了广泛的研究，但其他毒素（例如 anatoxin-a (ATX) 及其结构类似物）以及产生这些毒素的蓝藻类群仍有待详细研究。本研究调查了 ATX、CYN 及其同源物的水平以及anaC和cyrJ的发生水华中的基因在捷克共和国的 16 个地点出现，这些地点是根据潜在毒素生产者的存在而预先选择的。此外，我们还研究了实验室可用的一系列菌株中的毒素和基因。在来自捷克共和国的 5 个天然生物质样品中检测到 ATX 及其同源物 HATX（最大浓度为每克干重 2.8 微克）。有趣的是，anaC在任何这些毒素阳性生物质样品中都未检测到编码 ATX 生产的基因。蓝藻实验室菌株中 ATX 同源物的浓度比原始 ATX 的浓度高约 10 倍，这需要进一步研究解决 ATX 类似物的水平和危害。关于 CYN 和 7-脱氧 CYN（本研究未分析其他 CYN 同系物）——在捷克共和国的一个小池塘中发现这些毒素的浓度分别为 4.3 和 2.7 微克/克生物质干重（对应于溶解浓度）高于每升 1 微克）。CYN 阳性样本主要是产生 CYN 的类群Raphidiopsis ( basionym Cylindrospermopsis)和Cuspidothrix. 我们还证实了在这个自然绽放的样本中存在特定的cyrJ基因。据我们所知，这是第一项将Raphidiopsis ( Cylindrospermopsis )和Cuspidothrix作为欧洲CYN生产者的研究。这一观察结果需要进一步研究，因为随着全球变化，它们在（中）欧越来越多地出现。本研究证明了在评估淡水中的危险蓝藻及其毒素时使用组合（分类、分析和分子）方法的重要性。