AM真菌菌丝际解磷细菌促进土壤有机磷高效利用的作用机理

Aiming at the question of high phosphorus accumulation and low utilization of phosphorus fertilizer in Chinese farmland, how to improve the utilization efficiency of soil phosphorus has been concerned as an important issue for increasing efficiency by reducing phosphorus input. Microorganism is a main driver for biogeochemical cycle of soil phosphorus, and it is a key process to improve the utilization efficiency of soil phosphorus by the synergistic interactions among various microorganisms. However, the key process and mechanism of organic P turnover mediated by functional microbe in the hyphosphere remains poorly understood. In this project, functional groups and their genes expression of bacteria associated with extraradical mycelia of AM fungi in response to environmental factors were studied with the combination of a compartmented cultivation system, field in situ experiment and molecular microbial ecology techniques (high-throughput sequencing, high-throughput qPCR and so on), and their contribution of efficient utilization of soil phosphorus was evaluated. Organic phosphorus turnover was enhanced through C/P ratio, which will provide reliable theoretical basis for improving utilization efficiency of soil phosphorus and provide scientific supports and effective ways for achieving goal of increasing efficiency by reducing phosphorus input.

针对我国农田土壤磷素高积累和磷肥当季利用率低的问题，如何提高土壤累积态磷的利用效率是实现减磷增效的重大问题。微生物是驱动土壤磷素生物化学地球循环的主要因子，但是功能微生物调控的土壤磷素周转的关键过程和作用机理仍然知之甚少。本项目拟以AM真菌菌丝际定殖的解磷细菌为切入点，结合室内模拟和田间原位试验，利用高通量测序技术研究AM真菌根外菌丝上定殖的细菌功能组群的特征对环境因子的响应；采用高通量定量PCR方法量化菌丝际细菌功能基因的表达，并与土壤有机磷的周转和植物磷吸收建立关系，评价其对土壤磷素高效利用的贡献；通过碳磷比调控功能微生物的代谢活性，强化土壤磷素周转的关键过程，从而揭示土壤磷素周转和高效利用的微生物作用机理，为磷肥的减施增效提供理论基础和调控途径。

土壤磷素的高效利用是实现磷肥减施增效的关键，利用土壤功能微生物的解磷潜力及其协同互作是实现土壤磷素高效利用和环境可持续发展的可靠途径。本项目以AM真菌菌丝际定殖的解磷细菌为切入点，结合室内模拟试验（两室隔网培养系统）和田间原位试验，利用高通量测序和实时荧光定量PCR等微生物分子生态学技术，从解磷微生物功能基因的角度研究AM真菌根外菌丝上定殖的解磷细菌关键功能组群及其基因丰度对环境因子的响应，量化关键基因与土壤有效磷的关系以及建立解磷微生物功能最大化的调控方法，主要结果如下：（1）有机磷水平显著改变AM真菌菌丝际解磷细菌phoD基因群落结构和组成，而对编码bpp基因的细菌群落不产生影响；（2）碳源种类显著改变AM真菌菌丝际解磷细菌（编码phoD和bpp基因）群落组成，而不影响其群落结构；（3）供碳强度显著改变AM真菌菌丝际解磷细菌（编码phoD和bpp基因）群落结构和组成；（4）碳磷比显著改变AM真菌菌丝际解磷细菌phoD基因群落结构、组成和基因丰度，而不会改变编码bpp基因的细菌群落结构、组成和基因丰度；（5）AM真菌菌丝际解磷细菌phoD和bpp基因丰度由低磷诱导，而且与土壤有效磷含量之间存在显著的负相关关系；（6）土壤有效磷和土壤pH分别是驱动解磷细菌phoD和bpp群落变化的首要环境因子；（7）碳添加有利于维持AM真菌菌丝际解磷细菌（编码phoD和gcd基因）共生网络稳定性。这些结果加深了关键功能基因对磷代谢重要生物学过程的认识，为揭示解磷功能微生物在土壤有机磷周转中的作用机理提供了理论依据，也为实现农田土壤磷素的高效利用提供了有效的调控方法。