Freshwater bloom‐forming cyanobacteria densely grow in the aquatic environments, leading to an increase in the viral‐contact rate. They possess numerous antiviral genes, as well as cell differentiation‐ and physiological performance‐related genes, owing to genome expansion. Their genomic features and unique lifestyles suggest that they coexist with cyanoviruses in ways different from marine cyanobacteria. Furthermore, genome contents of isolated freshwater bloom‐forming cyanobacterial viruses have little in common with those of marine cyanoviruses studied to date. They lack the marine cyanoviral hallmark genes that sustain photosynthetic activity and redirect host metabolism to viral reproduction; therefore, they are predicted to share metabolisms and precursor pools with host cyanobacteria to ensure efficient viral reproduction and avoid nutrient deficiencies and antiviral response. Additionally, cyanovirus–cyanobacteria coexistence strategies may change as bloom density increases. Diverse genotypic populations of cyanoviruses and hosts coexist and fluctuate under high viral‐contact rate conditions, leading to their rapid coevolution through antiviral responses. The ancestral and newly evolved genotypes coexist, thereby expanding the diversity levels of host and viral populations. Bottleneck events occurring due to season‐related decreases in bloom‐forming species abundance provide each genotype within cyanobacterial population an equal chance to increase in prevalence during the next bloom and enhance further diversification.

中文翻译：

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淡水形成华藻的蓝细菌病毒：基因组特征，感染策略和与宿主共存。

淡水形成水华的蓝藻在水生环境中密集生长，从而导致病毒接触率增加。由于基因组的扩展，它们拥有许多抗病毒基因，以及与细胞分化和生理机能有关的基因。它们的基因组特征和独特的生活方式表明它们以与海洋蓝细菌不同的方式与蓝藻病毒共存。此外，分离的淡水形成蓝藻的蓝藻病毒的基因组含量与迄今为止研究的海洋蓝藻病毒的基因组含量几乎没有共同之处。它们缺乏维持光合作用并使宿主代谢重新定向到病毒繁殖的海洋蓝藻病毒标志基因。因此，预计它们与宿主蓝细菌共享新陈代谢和前体库，以确保有效的病毒繁殖并避免营养缺乏和抗病毒反应。此外，蓝藻病毒-蓝细菌共存策略可能会随着水华密度的增加而改变。蓝藻病毒和宿主的不同基因型种群在高病毒接触率条件下共存并波动，从而通过抗病毒反应迅速共同进化。祖先和新进化的基因型共存，从而扩大了宿主和病毒种群的多样性水平。由于与开花相关的物种丰度与季节相关的减少而发生的瓶颈事件为蓝藻种群中的每个基因型提供了在下一次开花期间增加患病率并增强进一步多样化的机会。