The distribution characteristics of the major capsid gene (g23) of T4-type phages in paddy floodwater in Northeast China

Our previous study revealed the high diversity of the major capsid gene (g23) of T4-type phages that existed in the paddy field soils in Northeast China. In this study, the phylogeny and genetic diversity of the g23 gene in the paddy floodwater samples collected from five sampling sites at three sampling times during the rice (Oryzasativa L.) growth season in Northeast China are reported. In total, 104 different g23 clones were isolated, among which 50% of the clones exhibited the highest identities with the clones retrieved in paddy soils and upland black soils. The remaining clones had the highest identities with lake origins. Phylogenetic analysis revealed that 43% of the g23 clones grouped into three novel subgroups which included the clones unique to paddy floodwater, and no g23 sequences obtained in paddy floodwater fell into the paddy soil groups II, III, IV, V, VI, VII and NPC-A. UniFrac analysis of g23 clone assemblages demonstrated that T4-type phage communities in paddy floodwater were changed spatially and temporally, and the communities were different from those in paddy soils. Further comparison of the g23 clone assemblages from different environments demonstrated that T4-type phages were biogeographically distributed, and the distribution was both affected by geographical separation and ecological processes across the biomes.