Genetic, Biochemical, and Physiological Characterization of the Plant Symbionts Sinorhizobium meliloti and Rhizobium leguminosarum

根瘤菌是一种革兰氏阴性土壤细菌，它与豆类相互作用，在根部产生固氮根瘤，从而使植物能够在缺氮条件下生活。对苜蓿中华根瘤菌的基因组进行了测序，并将其作为研究植物-微生物相互作用的模式菌。尽管早期结瘤所涉及的信号的遗传学和生物化学研究进展很快，但人们对新陈代谢如何影响植物-细菌相互作用的早期阶段知之甚少。无法利用豆科植物根部常见的糖会影响根瘤菌与植物的相互作用。新陈代谢受到影响的菌株，或者不能竞争根瘤占有率，或者不能形成有效的固氮共生，将被用作遗传工具，以确定有效关联所需的决定因素。参与这些过程的基因将从生理、遗传和生化方面进行表征，以确定它们如何在整个植物水平和分子水平上影响共生。对根瘤菌的研究对从事农业工作的人特别感兴趣，特别是在植物-微生物相互作用方面，然而，由于根瘤菌与许多其他细菌有共同之处，这项关于新陈代谢的工作可以扩展到更广泛的科学界，研究生物修复、药物开发或其他应用等问题。此外，所产生的知识还具有翻译的潜力，并适用于加拿大的接种行业。为豆类生产生产更好的接种剂的能力将大大减少农业所需的氮素投入，并导致更可持续的农业实践。

Rhizobium is a Gram-negative soil bacterium that interacts with legumes to produce nitrogen fixing nodules on the roots thus allowing the plant to live under nitrogen deficient regimes. The genome of Sinorhizobium meliloti is sequenced and has been adopted as a model bacterium in which to study plant-microbe interactions. Although the genetics and biochemistry of the signaling involved during early nodulation are rapidly progressing, comparatively little is understood about how metabolism affects these early stages of plant-bacteria interaction. The inability to utilize sugars that are commonly found around the roots of legume plants can affect how the rhizobia interact with the plant. Strains that are affected in metabolism, and are either unable to compete for nodule occupancy or are unable to form effective nitrogen fixing symbiosis will be used as genetic tools to identify determinants that are necessary for efficient associations. The genes involved in these processes will be characterized physiologically, genetically as well as biochemically to identify how they affect the symbiosis, both at a whole plant level, as well as at a molecular level. The study of rhizobia is of particular interest to those working in the agriculture, specifically in plant-microbe interactions, however, as rhizobia have commonalities with many other bacteria this work on metabolism can extend to a broader scientific community working on problems such as bioremediation, drug development or other applications. In addition, the knowledge generated also has the potential to be translational, and have applicability to Canada's inoculum industry. The ability to produce better inoculums for legume production will greatly decrease the nitrogen input needed for agriculture and lead to more sustainable agricultural practices.