BACKGROUND Members of the Roseobacter lineage are a major group of marine heterotrophic bacteria because of their wide distribution, versatile lifestyles and important biogeochemical roles. Bacteriophages, the most abundant biological entities in the ocean, play important roles in shaping their hosts' population structures and mediating genetic exchange between hosts. However, our knowledge of roseophages (bacteriophages that infect Roseobacter) is far behind that of their host counterparts, partly reflecting the need to isolate and analyze the phages associated with this ecologically important bacterial clade. METHODS vB_DshS-R4C (R4C), a novel virulent roseophage that infects Dinoroseobacter shibae DFL12T, was isolated with the double-layer agar method. The phage morphology was visualized with transmission electron microscopy. We characterized R4C in-depth with a genomic analysis and investigated the distribution of the R4C genome in different environments with a metagenomic recruitment analysis. RESULTS The double-stranded DNA genome of R4C consists of 36,291 bp with a high GC content of 66.75%. It has 49 genes with low DNA and protein homologies to those of other known phages. Morphological and phylogenetic analyses suggested that R4C is a novel member of the family Siphoviridae and is most closely related to phages in the genus Cronusvirus. However, unlike the Cronusvirus phages, R4C encodes an integrase, implying its ability to establish a lysogenic life cycle. A terminal analysis shows that, like that of λ phage, the R4C genome utilize the 'cohesive ends' DNA-packaging mechanism. Significantly, homologues of the R4C genes are more prevalent in coastal areas than in the open ocean. CONCLUSIONS Information about this newly discovered phage extends our understanding of bacteriophage diversity, evolution, and their roles in different environments.

中文翻译：

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一个新分离的迷迭香噬菌体代表了Siphoviridae家族的一个独特成员。

背景技术玫瑰杆菌属的成员由于其广泛的分布，多样化的生活方式和重要的生物地球化学作用而成为海洋异养细菌的主要群体。噬菌体是海洋中最丰富的生物实体，在塑造寄主的种群结构和介导寄主之间的遗传交换方面发挥着重要作用。但是，我们对噬菌体（感染玫瑰杆菌的噬菌体）的了解远远落后于其宿主宿主，部分反映了对分离和分析与这一具有生态重要性的细菌进化枝相关的噬菌体的需求。方法采用双层琼脂法分离vB_DshS-R4C（R4C），它是一种新型的能感染芝芝DFL12T的强力噬菌体。用透射电子显微镜观察噬菌体的形态。我们通过基因组分析对R4C进行了深入表征，并通过宏基因组募集分析研究了R4C基因组在不同环境中的分布。结果R4C的双链DNA基因组由36,291 bp组成，GC含量高达66.75％。它具有49个与其他已知噬菌体相比具有较低DNA和蛋白质同源性的基因。形态和系统发育分析表明R4C是Siphoviridae家族的一个新成员，并且与冠状病毒属的噬菌体关系最密切。但是，与冠状病毒噬菌体不同，R4C编码整合酶，暗示其建立溶原性生命周期的能力。最终分析表明，与λ噬菌体一样，R4C基因组也利用了“粘性末端” DNA包装机制。显着地，R4C基因的同源物在沿海地区比在公海中更为普遍。结论关于这种新发现的噬菌体的信息扩展了我们对噬菌体多样性，进化及其在不同环境中的作用的理解。