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

参与根际竞争和生存的根瘤菌基因特征根瘤菌是一种革兰氏阴性土壤细菌，它与豆类植物相互作用，在豆类植物的根部产生固氮根瘤，从而使豆类植物能够在缺氮条件下生活。尽管人们对结瘤的遗传学了解很多，关于细菌在结瘤前如何在土壤环境中生存/茁壮成长，人们知之甚少。这项研究提案将采用遗传/生化方法解决后一个问题。苜蓿中华根瘤菌的基因组被测序，并已被采纳为研究植物-微生物相互作用的模式细菌。该提案中的大部分工作将在这个系统中进行。这项工作涉及降解沙棘糖的基因和生化特性，沙棘糖是一种植物衍生糖，这是根瘤菌有效竞争结瘤所必需的。我们在这方面的工作结果使我们找到了一种与中心代谢途径突变体相关的新的植物表型。该表型表明，在实验室条件下提高寄主豆科植物的产量是可能的。为了更全面地了解苜蓿根瘤菌的这一中心代谢途径，人们也在进行研究。希望通过了解根瘤菌的基础生物学，所产生的知识可能与增强生物固氮有关。

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.