花垣铅锌尾矿废弃地地枇杷根际土壤细菌群落演替及功能预测

Bacterial Community Succession and Function Prediction in Rhizosphere Soil of Ficus tikoua in Lead and Zinc Tailings Wasteland

摘要: 看护植物介导的微斑块变化是尾矿废弃地等退化生态系统恢复过程中的活跃成分。以铅锌尾矿废弃地裸地为对照(CK)，不同演替阶段的地枇杷斑块(初期Y、中期M和后期O)为研究对象，采用16S rRNA高通量测序技术对不同演替过程中地枇杷根际土壤细菌数据进行数据挖掘和分析，运用PISCRUSt2功能预测分析探讨了铅锌尾矿废弃地上不同演替过程中地枇杷根际细菌群落变化及碳、氮和磷代谢特征。结果表明：1) 根际细菌优势门主要为变形菌门、蓝细菌门、绿弯菌门和放线菌门等，随着演替正向进行，蓝细菌门和绿弯菌门相对丰度逐渐降低，变形菌门和放线菌门相对丰度增加。优势属类群中鞘脂单胞菌属、Gaiella属、硫杆菌属和短波单胞菌属等的相对丰度逐渐降低，与之相反，红杆菌属、假单胞菌属、木洞菌属、慢生根瘤菌属和玫瑰单胞菌属的相对丰度则逐渐增加，典型对应分析(CCA)结果显示，有效磷(AP)和总磷(TP)与根际细菌物种分布的决定系数R2分别为0.8507 (P = 0.001)和0.9373 (P = 0.001)；2) 参与碳固定的6条途径中，以3-羟基丙酸双循环的总关键基因丰度最高，其次为卡尔文循环，随演替正向进行，根际细菌固碳潜力逐渐增加；3) 参与固氮反应的功能酶基因丰度以Y阶段最高，硝化反应的功能酶基因丰度随演替正向进行而逐渐增加，参与N代谢的所有功能基因中异化性硝酸盐还原反应(DNRA)的基因丰度最高，并在O阶段达到最大；4) 有机磷矿化与无机磷溶解的基因丰度均随演替正向进行而逐渐增加，有机磷运输基因丰度随演替正向进行而增加，但无机磷酸盐运输的基因总丰度却显著高于前者。综上所述，随着地枇杷斑块演替的正向进行，地枇杷根际土壤细菌的群落结构与组成发生了显著变化，TP和AP是这种变化的关键环境因子，根际土壤细菌群落以3-羟基丙酸双循环途径为主要的固碳方式，硝态氮还原以DNRA为主，使尾矿废弃地的土壤质量得到明显改善，然而以无机磷酸盐同化为主要方式的P代谢特征表明尾矿废弃地以地枇杷为主的斑块演替仍处于生态演替的初级阶段。

Abstract: Micropatch changes which mediated by nurse plants are the active factor in the restoration process of damaged ecosystems, such as tailings and other wasted land. We took the bare land of lead and zinc tailings wasteland as the control (CK), Ficus tikoua patches at different succession stages (early Y, middle M and late O) as the research objects, We compaired 16S rRNA sequences to explore and analyze the bacteria and its community variation in rhizosphere soil of F. tikoua in different succession stages, also detected carbon, nitrogen and phosphorus changes in rhizosphere bacterial of F. tikoua in different succession processes based on these, we tried to predict function of bacterial community by using PISCRUSt2. Results showed that 1) the dominant phyla of rhizosphere bacterial communities were Proteobacteria, Cyanobacteria, Chloroflexi and Actinobacteria, etc. With the progressive succession, the relative abundance of Cyanobacteria and Chloroflexi gradually decreased, while the relative abundance of Proteobacteria and Actinobacteria increased. The relative abundances of Sphingomonas, Gaiella, Thiobacillus and Brevundimonas in the dominant genera decreased gradually, whereas the relative abundances of Rhodobacter, Pseudomonas, Woodsholea, Bradyrhizobium and Roseomonas increased gradually, and the canonical correspondence analysis (CCA) showed that the determining coefficients R2 of available phosphorus (AP) and total phosphorus (TP) and rhizosphere bacterial species distribution were 0.8507 (P = 0.001) and 0.9373 (P = 0.001) respectively; 2) Among the 6 pathways involved in carbon fixation, the abundance of total key genes in the 3-hydroxypropionic acid double cycle was the highest, followed by the Calvin cycle. With progressive succession, the carbon sequestration potential of rhizosphere bacteria gradually increased; 3) The abundance of functional enzyme genes involved in nitrogen fixation reaction was the highest at the Y stage, and the abundance of functional enzyme genes in nitrification reaction gradually increased with the progression of succession. Among all functional genes involved in N metabolism, the abundance of genes involved in DNRA was the highest, and reached the maximum at the O stage; 4) The gene abundance of both organic phosphate mineralization and inorganic phosphorus dissolution gradually increased with the progressive succession. Although the gene abundance of organic phosphorus transport increased with the progressive succession, the total gene abundance of inorganic phosphate transport was significantly higher than that of the former. In summary, with the forward progression of F. tikoua patch succession, the bacterial community structure and composition in rhizosphere soil changed significantly, and total and available phosphorus were the key environmental factors for such changes. The bacterial community in rhizosphere soil used 3-hydroxypropionic acid double cycle as the main carbon sequestration method, and the nitrate nitrogen reduction in rhizosphere soil was mainly DNRA, which significantly improves the soil quality of tailings wasteland. However, the characteristics of P metabolism based on inorganic phosphate assimilation showed that the patch succession dominated by F. tikoua in tailings wasteland was still in the primary stage of ecological succession.