多金属抗性植物促生细菌强化蔬菜消减重金属的效应及其机理

Biologically based, eco-friendly and more effective methods are required to reduce heavy metal contamination. Phytostabilisation techniques associated with soil microbe is an emerging area of in situ safe utilization of multi-metal overproof farmlands, and will contribute to ensure the safety of agricultural production and the improvement of agricultural ecological environment. A thorough understanding of heavy-metal stress responses in plants could help identify patterns of biological responses, disclose underlying mechanisms of detoxification, and identify genes or proteins involved in stress tolerance. However, the molecular mechanisms underlying vegetables inoculated with metal resistant PGPRs responses to heavy metal stress are poorly understood. (1)Contaminant degrading bacteria will be screened out on the basis of their ability to solubilize phosphates, produce plant normones (IAA), siderophere, polyamine, the role of the metal resistent PGPRs in plant growth enhancement and their ability to deminish the toxic effect that heavy metal has on vegetable growth and quality. (2)The aim of this work is the evaluation of decontamination effect and the key factors of heavy metal resistant PGPRs (plant-growth promoting rhizobacteria) on vegetables for in situ safe utilization of multi-metal overproof farmlands. (3)Using the morphological, physiological, protemic and genetic methods, we would analyze various characterizations of heavy metal stress response in vegetables inoculated with metal resistant PGPRs (wild type and mutant), such as vegetables growth, metal uptake and transfer factor, antioxidant enzymes activity, endogenous polyamine contents, proteomic changes, genes involved in polyamines metabolism process, and so on. The objective of the current study is to investigate whether PGPR inoculation influences vegetables yield and quality, decreases plant metal accumulation, soil fertility and the structure of the rhizosphere bacterial community. We would evaluate the effect of plant-PGPRs rhizoremediation on the improvement of the ecological environment and quality of vegetables for future food security. The experimental investigation described here intends to further contribute to the molecular mechanism responsible for decontamination existing in PGPRs assisted vegetables and the development of metal resistant PGPRs accelerating phytostabilisation techniques.

在保证农产品安全生产和改善农业生态环境的前提下，针对重金属轻度、中度污染菜地，筛选高效阻控和消减重金属的功能微生物资源，探究其生理生化和遗传分子机制，明确功能细菌强化蔬菜吸收和消减重金属的效应及其影响因素；以功能细菌阻控消减蔬菜重金属的典型模型为重点材料，采用功能细菌（野生型和突变型）诱导处理，比较分析功能细菌协同作用模式下蔬菜的生长特征、抗氧化酶系统、多胺代谢规律、蛋白质组和相关基因表达等的差异，在根际原位修复的前提下研究功能细菌改善重金属超标农田土壤质量和蔬菜品质的机理，以期从生态学、植物生理学、蛋白质组学和基因水平等角度揭示功能细菌强化蔬菜消减重金属的机理，为功能细菌强化蔬菜生产生境的修复提供科学理论基础和技术支撑。

在保证农产品安全生产和改善农业生态环境的前提下，针对重金属轻度、中度污染农田，筛选安全高效的重金属钝化细菌，强化重金属钝化细菌降低蔬菜重金属含量的机理研究。本项目通过细菌分泌胞外多糖、H2S、多胺等特性，筛选获得多株阻控作物吸收重金属的细菌菌株Serratia liquefaciens CL-1、Bacillus thuringiensis X30、B. megaterium H3、B. amyloliquefaciens P29、Cupriavidus necator Q2-8等，建立功能菌株阻控小白菜、生菜、辣椒、茄子、萝卜等蔬菜以及油菜、小麦、水稻等作物吸收重金属的技术，在盆栽和田间试验中显著降低作物Pb、Cd和As含量（20%以上），促进作物生长，提高作物营养品质，改良土壤肥力。发现菌株CL-1通过细胞吸附固定重金属；在Cd胁迫下可使油菜生物量提高12-32%，油菜籽粒中Cd的含量降低了22-35%；与不接菌对照相比，菌株CL-1能够显著提高油菜根际土中多胺含量（70-244%）和产精氨酸脱羧酶细菌的比例（21-49%），能显著降低油菜根际土壤中基因cadA的拷贝数、显著提高油菜根际土壤中基因aguA、ureC的拷贝数（20-48%、27-67%），分泌多胺、NH4+等提高土壤pH，显著降低油菜根际土中DTPA提取态Cd含量。Cd/As复合胁迫下菌株Q2-8显著降低扬麦16籽粒中Cd/As含量（21-30%, 27-29%）和根际土壤有效态Cd/As含量(15-28%, 22-38%)，显著提高小麦土壤中基因arsM和Leptothrix spp.相对丰度，有利于土壤中铁锰氧化物的形成，增强土壤对重（类）金属的吸附能力，从而减少有效态重（类）金属含量。而且接种菌株Q2-8使小麦根中参与能量合成、蛋白质稳态、含硫化合物代谢、转运、细胞壁合成等229个蛋白差异表达，减少Cd/As向地上部转移，缓解Cd/As对小麦的毒害。发现菌株P29细胞及其胞外多糖分子结构中的羟基、羧基、酰胺基和磷酰基等官能团和葡萄糖、甘露糖特征峰在吸附Pb前后发生变化，在田间试验中P29降低辣椒和茄子中Pb含量，提高土壤多糖含量和2 mm以上团聚体比例，显著改善根际土壤性质。以上研究结果为重金属钝化细菌强化作物生产生境的修复和农产品安全生产提供科学理论基础和技术支撑。