Phylogenetic Distribution of the Capsid Assembly Protein Gene (g20) of Cyanophages in Paddy Floodwaters in Northeast China

Numerous studies have revealed the high diversity of cyanophages in marine and freshwater environments, but little is currently known about the diversity of cyanophages in paddy fields, particularly in Northeast (NE) China. To elucidate the genetic diversity of cyanophages in paddy floodwaters in NE China, viral capsid assembly protein gene (g20) sequences from five floodwater samples were amplified with the primers CPS1 and CPS8. Denaturing gradient gel electrophoresis (DGGE) was applied to distinguish different g20 clones. In total, 54 clones differing in g20 nucleotide sequences were obtained in this study. Phylogenetic analysis showed that the distribution of g20 sequences in this study was different from that in Japanese paddy fields, and all the sequences were grouped into Clusters α, β, γ and ε. Within Clusters α and β, three new small clusters (PFW-VII∼-IX) were identified. UniFrac analysis of g20 clone assemblages demonstrated that the community compositions of cyanophage varied among marine, lake and paddy field environments. In paddy floodwater, community compositions of cyanophage were also different between NE China and Japan.

已有大量研究揭示了海洋与淡水环境中蓝细菌噬菌体（cyanophages）的高度多样性，但目前学界对稻田生境下蓝细菌噬菌体的多样性仍知之甚少，尤其是中国东北地区（Northeast China, NE）。为阐明中国东北地区稻田淹水层中蓝细菌噬菌体的遗传多样性，本研究利用引物CPS1与CPS8对5份淹水样本的病毒衣壳组装蛋白基因（g20）序列进行扩增，并采用变性梯度凝胶电泳（Denaturing gradient gel electrophoresis, DGGE）区分不同的g20克隆。本研究共获得54个g20核苷酸序列存在差异的克隆。系统发育分析结果显示，本研究获得的g20序列分布模式与日本稻田中的相关序列存在差异，所有序列均被归入α、β、γ及ε簇。在α与β簇内，本研究还鉴定出3个全新的小型簇群（PFW-VII~PFW-IX）。对g20克隆群落的UniFrac分析表明，蓝细菌噬菌体的群落组成在海洋、湖泊与稻田生境间存在显著差异；在稻田淹水层中，中国东北地区与日本的蓝细菌噬菌体群落组成亦存在明显不同。