Cyanobacteria are important contributors to primary production in the open oceans. Over the past decade, various photosynthesis-related genes have been found in viruses that infect cyanobacteria (cyanophages). Although photosystem II (PSII) genes are common in both cultured cyanophages and environmental samples ^1-4 , viral photosystem I (vPSI) genes have so far only been detected in environmental samples ^5,6 . Here, we have used a targeted strategy to isolate a cyanophage from the tropical Pacific Ocean that carries a PSI gene cassette with seven distinct PSI genes (psaJF, C, A, B, K, E, D) as well as two PSII genes (psbA, D). This cyanophage, P-TIM68, belongs to the T4-like myoviruses, has a prolate capsid, a long contractile tail and infects Prochlorococcus sp. strain MIT9515. Phage photosynthesis genes from both photosystems are expressed during infection, and the resultant proteins are incorporated into membranes of the infected host. Moreover, photosynthetic capacity in the cell is maintained throughout the infection cycle with enhancement of cyclic electron flow around PSI. Analysis of metagenomic data from the Tara Oceans expedition ⁷ shows that phages carrying PSI gene cassettes are abundant in the tropical Pacific Ocean, composing up to 28% of T4-like cyanomyophages. They are also present in the tropical Indian and Atlantic Oceans. P-TIM68 populations, specifically, compose on average 22% of the PSI-gene-cassette carrying phages. Our results suggest that cyanophages carrying PSI and PSII genes are likely to maintain and even manipulate photosynthesis during infection of their Prochlorococcus hosts in the tropical oceans.

中文翻译：

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编码光系统I和II蛋白的肌病毒可增强感染的原球菌细胞中的循环电子流。

蓝细菌是公海初级生产的重要贡献者。在过去的十年中，在感染蓝细菌（蓝藻）的病毒中发现了各种与光合作用相关的基因。尽管光系统II（PSII）基因在培养的噬菌体和环境样品^1-4中都很常见，但到目前为止，仅在环境样品中检测到病毒光系统I（vPSI）基因^5,6。在这里，我们采用了针对性的策略从热带太平洋分离出一个噬菌体，该噬菌体带有一个带有七个不同PSI基因（psaJF，C，A，B，K，E，D）以及两个PSII基因的PSI基因盒（ psbA，D）。该蓝噬菌体P-TIM68属于T4样肌病毒，衣壳长，尾巴长而收缩，可感染Prochlorococcus sp。菌株MIT9515。来自两个光系统的噬菌体光合作用基因在感染过程中表达，并将所得蛋白质掺入被感染宿主的膜中。此外，在整个感染周期中，随着PSI周围循环电子流的增强，细胞中的光合作用能力得以维持。塔拉海洋考察⁷的宏基因组学数据分析结果显示，携带PSI基因盒的噬菌体在热带太平洋中非常丰富，占高达T4样蓝藻的28％。它们也存在于热带印度洋和大西洋中。具体而言，P-TIM68群体平均占携带PSI基因盒的噬菌体的22％。我们的结果表明，携带PSI和PSII基因的蓝藻在热带海洋中感染原球菌宿主期间可能会维持甚至操纵光合作用。