Characterization of rhizobium genes involved in competition and survival in the rhizosphere

根瘤菌是一种革兰氏阴性土壤细菌，它与豆科植物相互作用，在豆科植物的根上产生固氮根瘤，从而使植物能够在缺氮条件下生存。虽然人们对结瘤的遗传学了解很多，但对细菌在结瘤之前如何在土壤环境中生存/茁壮成长知之甚少。本研究计划将采用遗传/生化方法解决后一个问题。meliloti Sinorhizobium meliloti基因组测序已被采用作为研究植物与微生物相互作用的模式细菌。本提案中的大部分工作将在该系统中进行。这项工作涉及降解鼠李糖的基因的遗传和生化特征，鼠李糖是根瘤菌有效竞争结瘤所必需的一种植物衍生糖。我们在这一领域的工作结果使我们发现了一种与中心代谢途径突变相关的新型植物表型。表型表明，在实验室条件下，有可能增加寄主豆科植物的产量。为了更充分地了解这一中心代谢途径，也正在研究S. meliloti。希望通过了解根瘤菌的基本生物学，所产生的知识可能与加强生物固氮有关。

Characterization of Rhizobium Genes Involved in Competition and Survival in the Rhizosphere 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.  Although a great deal is known about the genetics of nodulation, very little is understood about how bacteria survive/thrive in the soil environment prior to nodulation.  This research proposal will address this latter problem employing a genetic/biochemical approach.  The genome of  Sinorhizobium meliloti is sequenced and has been adopted as a model bacterium in which to study plant-microbe interactions.  The majority of the work in this proposal will be carried out in this system.  The work involves the genetic and biochemical characterization of genes that degrade  rhamnose, a plant derived sugar, that is necessary for Rhizobium to compete effectively for nodulation.  The results of our work in this area have led us to find a novel plant phenotype that is associated with a central metabolic pathway mutant.  The phenotype suggests that it is possible to increase the yield of the host legume under laboratory conditions.  To more fully understand this central metabolic pathways of S. meliloti are also being studied.  It is hoped that by understanding the fundamental biology of Rhizobium the knowledge generated may be relevant to enhancing biological nitrogen fixation.