Marine cyanobacteria of the genera Synechococcus and Prochlorococcus are the most abundant photosynthetic organisms on earth, spanning vast regions of the oceans and contributing significantly to global primary production. Their viruses (cyanophages) greatly influence cyanobacterial ecology and evolution. Although many cyanophage genomes have been sequenced, insight into the functional role of cyanophage genes is limited by the lack of a cyanophage genetic engineering system. Here, we describe a simple, generalizable method for genetic engineering of cyanophages from multiple families, that we named REEP for REcombination, Enrichment and PCR screening. This method enables direct investigation of key cyanophage genes, and its simplicity makes it adaptable to other ecologically relevant host-virus systems. T7-like cyanophages often carry integrase genes and attachment sites, yet exhibit lytic infection dynamics. Here, using REEP, we investigated their ability to integrate and maintain a lysogenic life cycle. We found that these cyanophages integrate into the host genome and that the integrase and attachment site are required for integration. However, stable lysogens did not form. The frequency of integration was found to be low in both lab cultures and the oceans. These findings suggest that T7-like cyanophage integration is transient and is not part of a classical lysogenic cycle.

Synechococcus和Prochlorococcus属的海洋蓝藻是地球上最丰富的光合生物，横跨广阔的海洋区域，对全球初级生产做出了重大贡献。它们的病毒（噬藻体）极大地影响了蓝藻的生态学和进化。尽管已经对许多噬菌体基因组进行了测序，但由于缺乏噬菌体基因工程系统，对噬菌体基因功能作用的深入了解受到限制。在这里，我们描述了一种用于对来自多个家族的噬藻体进行基因工程的简单、可推广的方法，我们将其命名为 REEP，用于重组、富集和 PCR 筛选。这种方法可以直接研究关键的噬藻体基因，其简单性使其适用于其他生态相关的宿主病毒系统。T7 样噬藻体通常携带整合酶基因和附着位点，但表现出溶解感染动力学。在这里，我们使用 REEP 研究了它们整合和维持溶原性生命周期的能力。我们发现这些噬藻体整合到宿主基因组中，整合需要整合酶和附着位点。然而，没有形成稳定的溶原菌。在实验室培养和海洋中发现整合的频率很低。这些发现表明，T7 样噬藻体整合是短暂的，不是经典溶原循环的一部分。