Junier Pilar, Cailleau Guillaume, Fatton Mathilda, Udriet Pauline, Hashmi Isha, Bregnard Danae, Corona-Ramirez Andrea, Francesco Eva di, Kuhn Thierry, Mangia Naïma, Zhioua Sami, Hunkeler Daniel, Bindschedler Saskia, Sieber Simon, Gonzalez Diego
Laboratory of Microbiology, University of Neuchâtel, Switzerland.
Centre for Hydrogeology and Geothermics, University of Neuchâtel, Switzerland.
Water Res X. 2024 Sep 4;24:100252. doi: 10.1016/j.wroa.2024.100252. eCollection 2024 Sep 1.
Over the last two decades, proliferations of benthic cyanobacteria producing derivatives of anatoxin-a have been reported in rivers worldwide. Here, we follow up on such a toxigenic event happening in the Areuse river in Switzerland and investigate the diversity and genomics of major bloom-forming riverine benthic cyanobacteria. We show, using 16S rRNA-based community profiling, that benthic communities are dominated by Oscillatoriales. We correlate the detection of one sequence variant matching the species with the presence of anatoxin-a derivatives and use long-read metagenomics to assemble complete circular genomes of the strain. The main dihydro-anatoxin-a-producing strain in the Areuse is distinct from strains isolated in New Zealand, the USA, and Canada, but forms a monophyletic strain cluster with them with average nucleotide identity values close to the species threshold. Compared to the rest of the genus, the toxin-producing strains encode a 15 % smaller genome, lacking genes for the synthesis of some essential vitamins. Toxigenic mats harbor a distinct microbiome dominated by proteobacteria and bacteroidetes, which may support cyanobacterial growth by providing them with essential nutrients. We recommend that strains closely related to be monitored internationally in order to help predict and mitigate similar cyanotoxic events.
在过去二十年中，全球河流中均有产类anatoxin-a衍生物的底栖蓝藻大量繁殖的报道。在此，我们追踪了瑞士阿雷use河发生的此类产毒事件，并调查了主要形成水华的河流底栖蓝藻的多样性和基因组学。我们通过基于16S rRNA的群落分析表明，底栖群落以颤藻目为主。我们将与该物种匹配的一个序列变体的检测与anatoxin-a衍生物的存在相关联，并使用长读长宏基因组学来组装该菌株的完整环状基因组。阿雷use河中主要产生二氢anatoxin-a的菌株与在新西兰、美国和加拿大分离的菌株不同，但与它们形成一个单系菌株簇，平均核苷酸同一性值接近物种阈值。与该属的其他菌株相比，产毒菌株的基因组小15%，缺少一些必需维生素合成的基因。产毒藻席拥有一个以变形菌门和拟杆菌门为主的独特微生物群落，它们可能通过为蓝藻提供必需营养来支持其生长。我们建议在国际上对与该菌株密切相关的菌株进行监测，以帮助预测和减轻类似的蓝藻毒素事件。
