Halary Sébastien, Duperron Sébastien, Kim Tiam Sandra, Duval Charlotte, Bernard Cécile, Marie Benjamin
Muséum National d'Histoire Naturelle, CNRS, UMR7245 Mécanismes de Communication et Adaptation des Micro-organismes, 12 rue Buffon, 75005, Paris, France.
UMR5557 Laboratoire d'Ecologie Microbienne, Université de Lyon, 43 bd du 11 novembre 1918, Villeurbanne, F-69622, Lyon, France.
ISME Commun. 2023 Jun 7;3(1):57. doi: 10.1038/s43705-023-00263-3.
Cyanobacteria are oxygenic photosynthetic bacteria that perform a substantial part of the global primary production. Some species are responsible for catastrophic environmental events, called blooms, which have become increasingly common in lakes and freshwater bodies as a consequence of global changes. Genotypic diversity is considered essential for marine cyanobacterial population, allowing it to cope with spatio-temporal environmental variations and to adapt to specific micro-niches in the ecosystem. This aspect is underestimated in the study of bloom development, however, and given little notice in studies of the ecology of harmful cyanobacteria. Here we compared the genomes of four strains of Aphanizomenon gracile, a species of filamentous toxinogenic cyanobacteria (Nostocales) found worldwide in fresh and brackish water. Millimeter-sized fascicles were isolated from a single water sample and have been maintained in culture since 2010. A comparative study revealed extensive heterogeneity in gene contents, despite similar genome size and high similarity indices. These variations were mainly associated with mobile genetic elements and biosynthetic gene clusters. For some of the latter, metabolomic analysis confirmed the production of related secondary metabolites, such as cyanotoxins and carotenoids, which are thought to play a fundamental role in the cyanobacterial fitness. Altogether, these results demonstrated that an A. gracile bloom could be a highly diverse population at low spatial scale and raised questions about potential exchanges of essential metabolites between individuals.
蓝藻是产氧光合细菌，在全球初级生产中发挥着重要作用。一些蓝藻物种会引发灾难性的环境事件，即水华，由于全球变化，水华在湖泊和淡水水体中变得越来越常见。基因型多样性被认为对海洋蓝藻种群至关重要，使其能够应对时空环境变化，并适应生态系统中的特定微生境。然而，在水华发展的研究中，这一方面被低估了，在有害蓝藻生态学研究中也很少受到关注。在这里，我们比较了四株纤细束丝藻的基因组，纤细束丝藻是一种丝状产毒蓝藻（念珠藻目），在世界各地的淡水和微咸水中都有发现。从单个水样中分离出毫米大小的藻束，自2010年以来一直在培养。一项比较研究表明，尽管基因组大小相似且相似性指数较高，但基因含量存在广泛的异质性。这些变异主要与移动遗传元件和生物合成基因簇有关。对于后者中的一些，代谢组学分析证实了相关次生代谢产物的产生，如蓝藻毒素和类胡萝卜素，它们被认为在蓝藻适应性中起重要作用。总之，这些结果表明，纤细束丝藻水华在低空间尺度上可能是一个高度多样化的种群，并引发了关于个体之间必需代谢产物潜在交换的问题。
