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，其与豆类相互作用以在豆类的根部产生固氮根瘤，从而允许植物在氮缺乏的情况下生存。苜蓿中华根瘤菌的基因组序列已被测序，并已被用作研究植物-微生物相互作用的模式细菌。虽然在早期植物化过程中涉及的信号传导的遗传学和生物化学正在迅速发展，但相对而言，人们对代谢如何影响植物-细菌相互作用的早期阶段知之甚少。不能利用豆类植物根部周围常见的糖会影响根瘤菌与植物的相互作用。不能利用植物细胞壁的一种成分鼠李糖，产生一种对根瘤占有没有竞争力的菌株，而不能利用半乳糖的菌株产生一种对根瘤占有更具竞争力的菌株。参与这些过程的基因将在遗传学和生物化学方面得到表征。此外，直接共聚焦成像将评估这些菌株中的每一种如何共生。如果这些技术可以用来生产更好的豆类生产接种物，那么从拟议的工作中产生的基本知识将与科学界以及加拿大人普遍相关。

Rhizobium is a Gram-negative soil bacterium that interacts with legumes to produce nitrogen fixing nodules on the roots of legumes 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. The inability to utilize rhamnose, a constituent of the plant cell wall, yields a strain that is uncompetitive for nodule occupancy, whereas a strain unable to use galactose gives rise to a strain that is more competitive for nodule occupancy.This research proposal will address the role the catabolism of these compounds plays during the symbiotic development. The genes involved in these processes will be characterized genetically and biochemically. In addition, direct confocal imaging will assess how each of these strains behaves symbiotically. The fundamental knowledge that will be generated from the proposed work will be relevant both to the scientific community as well as to Canadians generally if these technologies can be utilized to produce better inoculums for legume production.