阿特拉津胁迫下丛枝菌根与根际微生物互馈机制

Remediation atrazine contaminated soil by arbuscular mycorrhiza (AM) is closely related to rhizosphere soil microbial community structure, soil enzyme activity and other factors. Atrazine degradation bacterial community is the main degradation dynamics due to high degradation ability. There is a close relationship between its degradation efficiency and soil nitrogen levels and forms. Therefore, nitrogen cycle will be regarded as the breakthrough point in this study to research mutual feedback mechanism between AM and rhizosphere microorganisms under atrazine. In this study, inverted "T" shape symbiotic culture devices are employed. Medicago sativa inoculated with Glomus mosseae to remediation atrazine contaminated soil is regarded as research models, M. sativa inoculated with inactivation G. mosseae as reference control. First of all, root exudates as a medium, influence of AM on ecological characteristics of rhizosphere microbial under atrazine stress is investigated, including microbial community structure and abundance participateed in the nitrogen cycle, soil microorganism enzyme activity, respiration and microbial biomass nitrogen. Meanwhile, nitrogen nutrition of rhizosphere soil as a medium, the feedback regulation of rhizosphere microorganisms on physiological activity of AM is studied from the root vigor, root biomass, root surface area and root active absorption area. These results of the mutual feedback mechanism between AM and rhizosphere microorganisms under atrazine, will provide powerful evidence on the mechanism of AM remediation of atrazine contaminated soil, which is not yet clear.

丛枝菌根修复阿特拉津污染土壤受根际微生物群落结构、土壤酶活等因子影响。根际阿特拉津降解细菌因具备高降解能力而成为主要修复动力，其降解效率与土壤氮素水平、氮素形态密切相关。本研究以氮素循环为切入点，采用倒置“T型”共生培养装置，以苜蓿接种摩西球囊霉(Glomus mosseae, GM)修复阿特拉津污染土壤作为研究模型，以接种灭活GM菌剂作为空白对照。在阿特拉津胁迫下，以根系分泌物为介导，揭示丛枝菌根对根际微生物生态特征的影响机制，主要包括氮素循环微生物群落结构与丰度、土壤微生物的酶活、呼吸作用、微生物量氮四个方面；同时，以根际土壤氮素营养为介导，阐明根际微生物对丛枝菌根的反馈调节机制，主要以根系的活力、生物量、比表面积、根系活跃吸收面积作为衡量指标。从而构建阿特拉津胁迫下丛枝菌根与根际微生物的互馈模型，旨为丛枝菌根修复阿特拉津污染土壤尚未明确的作用机理提供理论支持。

丛枝菌根（arbuscular mycorrhiza，AM）修复阿特拉津污染土壤受根际微生物群落结构、土壤酶活等因子影响。根际阿特拉津降解细菌因具备高降解能力而成为主要修复动力。本研究首先利用Funneliformis mosseae形成丛枝菌根化紫花苜蓿（Medicago sativa）并施加10 mg/kg除草剂阿特拉津，当阿特拉津降解率达到50%时，分别采集未接种+未施药（NM.NA）、接种+未施药（AM.NA）、未接种+施药（NM.AT）和接种+施药（AM.AT）四种处理的根际土壤，通过16S rRNA高通量测序技术比较了根际土壤细菌群落结构及多样性的变化。研究结果表明，接种F. mosseae和施加阿特拉津均未对根际土壤细菌群落的α-多样性指数产生显著影响。接种F. mosseae提高了阿特拉津胁迫下根际土壤中具有阿特拉津降解潜力菌属Arthrobacter、Frankia和Stenotrophomonas的相对丰度，其中Arthrobacter受F. mosseae、阿特拉津及其二者交互作用的显著性影响。另外，接种处理仍然显著提高了阿特拉津胁迫下DHA、URE、ACP和ALP的活性（p <0.05）。与此同时，接种处理缓解了阿特拉津对苜蓿光合相关参数的显著抑制作用。通过叶绿体超显微结构观察可知，阿特拉津对苜蓿叶绿体中的类囊体结构和嗜锇颗粒位置产生了明显的破坏作用，接种F. mosseae虽然不能完全消除叶绿体受损，但在一定程度上维持了叶绿体进行光合作用场所结构的完整性。利用非靶向代谢组学技术分析菌根化和非菌根化根系在阿特拉津胁迫下的代谢组分差异可知，除了didymin、naringin 和hesperidin之外，其他（类）黄酮其及衍生物在菌根化处理中都表现为显著性上调（p<0.05），用以缓解阿特拉津带来了氧化压力。通过对接种F. mosseae、未接种苜蓿根系分泌物及空白处理GC-MS数据结果筛选分析表明，正辛酸（Octanoic Acid）是由AM 真菌F. mosseae侵染M. sativa引起根系特征性分泌物种类。总之，通过探求丛枝菌根与根际微生物群落之间的互馈机制，为丛枝菌根修复阿特拉津污染土壤尚未明确的作用机理提供有力佐证。同时，也为进一步利用丛枝菌根修复其他有机物污染土壤奠定理论基础。