Effects of long-term phosphorus application on phoD harboring bacterial community in calcareous soil

Abstract:

[Objective] This study was aimed to investigate the effects of long-term phosphorus (P) supply on the diversity, structure, composition and network characteristics of bacterial community encoding alkaline phosphatase gene and their relationship with the forms of soil organic P, so as to provide scientific basis for exploring the community characteristics of organic P cycling functional microorganisms and improving the mineralization and utilization of soil organic P.[Methods] Based on the long-term P application experiment in calcareous soil of wheat-maize rotation system in North China Plain (started in 2008), the experiment included six P levels:0, 12.5, 25, 50, 100, 200 kg P/hm² (P0, P12.5, P25, P50, P100 and P200 respectively) and the molecular forms of organic P in soil were determined by nuclear magnetic resonance (NMR), high-throughput sequencing technology was used to analyze the bacterial community of phoD gene (encoding alkaline phosphatase), and explore the bacterial community characteristics of phoD gene and its relationship with the forms of organic P in soil.[Results] With the increase of P supply level, the concentration of phosphate monoester did not change significantly, but the concentration of phosphate diester increased significantly; the α-diversity of the phoD harboring bacterial community was first unchanged (P0 to P50) and then decreased (P50 to P200), and the community structure of phoD harboring bacteria changed significantly. The dominant taxa named Pseudomonas and Masslis at genus level decreased significantly, while Mitsuaria and Kribbella increased significantly with the increase of P supply level. Mitsuaria was positively correlated with the concentration of available P in soil, and negatively correlated with the activity of phosphatase. There was a significant negative correlation between the relative abundance of Pseudomonas and the concentration of total organic P in soil, and a significant positive correlation between the relative abundance of Lysobacter and the concentration of total organic P in soil. In the network analysis, the proportion of positive edges was the highest in P0 treatment, followed by P50 treatment, and the lowest in P100 treatment. In the treatments of P0, P12.5, P25 and P50, specific keystone taxa such as Bradyrhizobium, Stackbrandtia, Burkholderia, Bradyrhizobium and Lysobacter were significantly correlated with the concentration of organic P (including total organic P, phosphate monoester and phosphate diester), however, the keystone taxa under P100 and P200 treatments has no significant correlation with the forms of organic P.[Conclusion] The levels of P supply significantly affected the physicochemical properties of soil, such as pH, the forms and quantities of organic P, and then affected the changes of α-diversity, community structure, community composition, network characteristics and keystone taxa of phoD harboring bacterial community.

Key words:nuclear magnetic resonance;molecular speciation of organic P;α-diversity;community composition;keystone taxa;phoD gene