Data_Sheet_1_phoD-harboring bacterial community composition dominates organic P mineralization under long-term P fertilization in acid purple soil.docx

IntroductionA better understanding of the regulatory role of microorganisms on soil phosphorous (P) mobilization is critical for developing sustainable fertilization practices and reducing P resource scarcity. The phoD genes regulate soil organic P (Po) mobilization.
MethodsBased on the long-term P application experiments in acid purple soil of maize system in Southwest China (started in 2010), the experiment included five P levels: 0, 16, 33, 49, and 65.5 kg P hm–2 (P0, P16, P33, P49, and P65.5, respectively). The molecular speciation of organic P in soil was determined by 31P-nuclear magnetic resonance (NMR), high-throughput sequencing technology, and real-time qPCR were used to analyze the bacterial community and abundance of phoD-harboring bacterial genes, exploring the bacterial community and abundance characteristics of phoD gene and its relationship with the forms of Po and alkaline phosphatase (ALP) activity in the soil.
ResultsThe results showed that the orthophosphate monoesters (OM) were the main Po speciation and varied by P fertilization in acid purple soil. ALP activity decreased as P fertilization increased. Co-occurrence network analysis identified the overall network under five P fertilizations. The keystone taxon base on the network showed that Collimonas, Roseateles, Mesorhizobium, and Cellulomonas positively correlated with both OM and Po. The random forest showed that Cellulomonas, Roseateles, and Rhodoplanes were the key predictors for ALP activity. The keystone taxon was a more important predictor than the dominant taxon for ALP, OM, and Po. The structural equation model (SEM) showed that soil organic matter (SOM), available P (AP), and OM were the main factors influencing the ALP by reshaping phoD-harboring bacteria alpha diversity, community composition, and phoD abundance.
DiscussionThe phoD-harboring bacterial community composition especially the keystone taxon rather than alpha diversity and abundance dominated the ALP activity, which could promote P utilization over an intensive agroecosystem. These findings improve the understanding of how long-term gradient fertilization influences the community composition and function of P-solubilizing microorganisms in acid purple soil.

引言：深入理解微生物对土壤磷（phosphorous, P）活化的调控作用，对于制定可持续施肥方案、缓解磷资源短缺至关重要。phoD基因（phoD）调控土壤有机磷（organic P, Po）的活化过程。
方法：本研究依托中国西南地区玉米种植体系下酸性紫色土的长期施磷定位试验（始于2010年），试验设置5个施磷梯度：0、16、33、49、65.5 kg P hm⁻²（分别记为P0、P16、P33、P49、P65.5）。采用31P-核磁共振（31P-nuclear magnetic resonance, NMR）技术测定土壤有机磷的分子形态，结合高通量测序技术与实时荧光定量PCR（qPCR）分析携带phoD基因的细菌群落组成与丰度，探究phoD基因的细菌群落结构与丰度特征，及其与土壤有机磷形态和碱性磷酸酶（alkaline phosphatase, ALP）活性的关联。
结果：研究结果显示，酸性紫色土中有机磷的主要形态为正磷酸单酯（orthophosphate monoesters, OM），其含量随施磷水平变化产生显著差异。碱性磷酸酶（ALP）活性随施磷量增加呈下降趋势。共现网络分析构建了5个施磷梯度下的整体关联网络；基于网络筛选得到的关键类群表明，Collimonas、Roseateles、Mesorhizobium及Cellulomonas与OM和Po均呈显著正相关。随机森林分析结果显示，Cellulomonas、Roseateles及Rhodoplanes是影响ALP活性的关键预测因子。相较于优势类群，关键类群对ALP、OM及Po的预测能力更强。结构方程模型（structural equation model, SEM）结果证实，土壤有机质（soil organic matter, SOM）、有效磷（available P, AP）及OM是通过重塑携带phoD基因的细菌的α多样性、群落组成及phoD基因丰度，进而调控ALP活性的核心影响因素。
讨论：携带phoD基因的细菌群落组成，尤其是其中的关键类群，而非α多样性与基因丰度，主导了ALP活性，该结论可用于提升集约化农田生态系统的磷素利用效率。本研究结果深化了对长期梯度施肥如何调控酸性紫色土中溶磷微生物群落组成与功能的认知。