Dissertation Research: Quorum Sensing Influences Soil Nitrogen Mineralization and Plant Nitrogen Availability.

论文研究：群体感应影响土壤氮素矿化和植物氮素有效性。土壤微生物氮素矿化为植物提供了大部分氮素营养，但土壤氮素主要是有机氮（几丁质、蛋白质、木质素和核苷酸）。 氮矿化的限速步骤可能是微生物胞外酶对这些大分子的消化。 植物对细菌的功能有一定的控制作用，新的证据表明，根分泌物可以破坏细菌-细菌通讯的主导机制（群体感应（QS））和QS控制的行为，如胞外酶的产生。 我们的第一个假设是，QS影响根际氮矿化，植物健康，通过增加土壤酶活性，由于在根际信号增加。 第二个假说是真菌、细菌和植物之间的跨界相互作用通过QS影响氮矿化。 微宇宙允许容易地进入根际操作QS通过信号添加，无机N库和N矿化的测量。 全细胞生物传感器，过程速率测量，分解人口和社区分析的组合将揭示植物控制根际氮矿化的程度，以及这种控制模式对植物氮积累的重要性。 建立这一点将改写当前的范式，即植物和微生物是彼此过剩的被动接受者，并为物种间的化学交流和竞争开创了新的先例。

ABSTRACTDissertation Research: Quorum sensing influences soil nitrogen mineralization and plant nitrogen availabilityRhizosphere microbial N mineralization provides plants the majority of their N nutrition, but most soil N is organic (chitin, proteins, lignoprotiens and nucleotides). The rate-limiting step in N mineralization may be digestion of these large molecules by microbial extracellular enzymes. Plants exert some control over bacterial function, and new evidence shows that root exudates can disrupt the dominant mechanism of bacterial-bacterial communication (quorum sensing (QS)) and QS-controlled behaviors, such as extracellular enzyme production. Our first hypothesis is that QS affects rhizosphere N mineralization, and plant health, by increasing soil enzyme activity due to increased signal in the rhizosphere. The second hypothesis is that cross-kingdom interactions in the rhizosphere between mycorrhizae, bacteria and plants affect N mineralization via QS. Microcosms allow easy access to the rhizosphere for manipulation of QS through signal addition, measurement of inorganic N pools and N mineralization. A combination of whole-cell biosensors, process rate measurements, decomposing population and community analyses will reveal the degree to which plants control rhizosphere N mineralization and how important this mode of control is for plant N accumulation. To establish this would be to rewrite the current paradigm that plants and microbes are the passive recipients of each other's excess, and set a new precedent for inter-species chemical communication and competition.