多环芳烃降解微生物对黄河三角洲土壤盐胁迫的响应机制研究

Soil salinization and pollutants of polycyclic aromatic hydrocarbons are both severe problem in the Yellow River delta. In this program, analysis of quantities and structure characteristics of soil microbial flora were conducted under different soil salinization degrees. Degenerate primers were designed for kinds of dioxygenases, to discuss responses of the numbers and diversities of PAHs-degrading genes under different soil salinity. Using Rhodococcus erythropolis as the PAHs degrading bacteria, with molecular biology methods of qPCR, RT-PCR and high-throughput sequencing technology, the gene transcription of key enzyme for phenanthrene degradation were analysis under different levels of salt stress. Meanwhile, physiology response characteristics would be revealed under salt stress. Efforts were made to explain the response mechanisms of PAH-degrading bacteria under salt stress, and reveal the relationships between biodegradation of PAHs and soil salinity. The results of this program would make clear of the mechanisms of microorganisms’ growth and metabolism in saline soils, and the knowledge of the usages of microorganisms under the extreme conditions. It could provide a reference to study the impact mechanism of environmental factors on the microbial degradation of organic pollutants

针对黄河三角洲土壤中同时存在的盐渍化和多环芳烃污染问题，分析不同盐渍化程度下土壤微生物的数量和菌群结构特征；设计针对多种双加氧酶的兼并引物，研究多环芳烃降解基因数量和多样性对土壤盐度的响应；采用qPCR、RT-PCR和高通量测序等分子生物学手段分析不同程度的盐胁迫对其红平红球菌降解菲关键酶基因转录水平的影响；同时研究菌株在盐胁迫下的生理应答。阐明盐胁迫下多环芳烃降解微生物的响应机制，揭示盐度对盐渍土壤中多环芳烃微生物降解性能的影响机理。本研究将更全面和系统的解析多环芳烃降解微生物在盐渍土壤中的存在状态和代谢特征，阐释微生物在极端环境条件下对有机污染的修复行为，并为研究环境要素对微生物降解有机污染物的影响机制提供借鉴。

黄河三角洲土壤微生物大多处于盐渍化和多环芳烃（PAHs）污染双重胁迫的特殊生境下，研究和揭示PAHs降解微生物对盐胁迫的响应机制，能够促进该地区PAHs污染土壤的高效生物修复。本项目通过野外调查和实验室模拟相结合的方式，掌握了黄河三角洲土壤微生物群落特征和盐胁迫下PAHs降解菌群、降解基因和关键酶基因表达及降解菌生理指标的响应，得出了以下结论：（1）自然条件下不同盐度的黄河三角洲土壤中，土壤盐浓度导致了微生物群落结构、菌群多样性和丰富度发生显著性差异；（2）通过实验室模拟不同盐度下多环芳烃污染土壤中菌群的演替过程，阐述了盐胁迫对土壤菌群多样性和群落结构组成的影响，揭示了高盐对土壤微生物的过滤器作用，验证了黄河三角洲自然环境中盐胁迫与土壤微生物群落演化的关系；（3）通过研究多环芳烃降解菌在不同程度盐胁迫下的响应，在基因水平上解释了高盐土壤中多环芳烃降解率降低原因，是由于大量携带关键降解基因的PAHs降解菌株在盐胁迫下发生凋亡或休眠；（4）通过对土壤中的相关酶活性和PAHs降解关键基因表达的分析，验证了多环芳烃降解微生物在应对盐胁迫的过程中，微生物基因表达和功能发挥均会受到抑制；（5）通过分析多环芳烃降解菌在盐胁迫环境中的外观形貌和细胞膜组成变化，揭示了微生物的应对盐胁迫环境时的个体形态和膜脂肪酸含量等生理特征，均随着盐度的升高而发生改变，如此来适应不利环境，提高自身生存能力。研究结果更全面和深入的解析了多环芳烃降解菌在黄河三角洲盐环境中的存在状态和响应特征，能够为极端环境下应用微生物修复有机污染物提供理论基础和数据支撑。