It is generally recognized that phages are a mortality factor for their bacterial hosts. This could be particularly true in spring phytoplankton blooms, which are known to be closely followed by a highly specialized bacterial community. We hypothesized that phages modulate these dense heterotrophic bacteria successions following phytoplankton blooms. In this study, we focused on Flavobacteriia, because they are main responders during these blooms and have an important role in the degradation of polysaccharides. A cultivation-based approach was used, obtaining 44 lytic flavobacterial phages (flavophages), representing twelve new species from two viral realms. Taxonomic analysis allowed us to delineate ten new phage genera and ten new families, from which nine and four, respectively, had no previously cultivated representatives. Genomic analysis predicted various life styles and genomic replication strategies. A likely eukaryote-associated host habitat was reflected in the gene content of some of the flavophages. Detection in cellular metagenomes and by direct-plating showed that part of these phages were actively replicating in the environment during the 2018 spring bloom. Furthermore, CRISPR/Cas spacers and re-isolation during two consecutive years suggested that, at least part of the new flavophages are stable components of the microbial community in the North Sea. Together, our results indicate that these diverse flavophages have the potential to modulate their respective host populations.

人们普遍认为，噬菌体是其细菌宿主的致死因素。这在春季浮游植物大量繁殖中尤其如此，众所周知，高度专业化的细菌群落紧随其后。我们假设噬菌体在浮游植物大量繁殖后调节这些密集的异养细菌序列。在这项研究中，我们专注于黄杆菌属，因为它们是这些水华期间的主要反应者，并且在多糖的降解中具有重要作用。使用基于培养的方法，获得 44 个裂解黄杆菌噬菌体（flavophages），代表来自两个病毒领域的 12 个新物种。分类学分析使我们能够描绘出 10 个新的噬菌体属和 10 个新的科，其中 9 个和 4 个分别没有以前培养的代表。基因组分析预测了各种生活方式和基因组复制策略。一种可能与真核生物相关的宿主栖息地反映在一些噬黄体的基因含量中。细胞宏基因组和直接电镀的检测表明，这些噬菌体的一部分在 2018 年春季开花期间在环境中积极复制。此外，连续两年的 CRISPR/Cas 间隔和重新分离表明，至少有一部分新的噬黄体是北海微生物群落的稳定成分。总之，我们的结果表明，这些不同的黄体素有可能调节它们各自的宿主种群。