Plasmid biology of Rhizobium leguminosarum

根瘤菌是一种细菌，它能在豌豆、豆类、小扁豆和紫花苜蓿等豆科植物的根部形成固氮根瘤，这一点值得注意。它们能够让这些植物在不添加合成含氮化肥的情况下生长，而合成含氮化肥的生产和应用在化石燃料消耗方面成本很高，这使得它们在可持续农业中极其重要。生产更高效、更具竞争力的根瘤菌作为豆科植物的接种剂是生物技术的主要目标。然而，引进的根瘤菌之间的相互作用，以及环境中菌株之间遗传转移的潜力，还没有被很好地了解。根瘤菌在细菌中的不同寻常之处在于，它们拥有庞大而复杂的基因组，通常由一条染色体和几个被称为质粒的非常大的染色体外遗传元件组成。这些质粒往往非常稳定，其中一些性质介于质粒和染色体的性质之间。这项提案将重点放在

Rhizobia are bacteria that are notable for their ability to form nitrogen-fixing nodules on the roots of legume plants, such as peas, beans, lentils and alfalfa. Their ability to allow these plants to grow without addition of synthetic nitrogen-containing fertilizers, whose production and application has a high cost in fossil fuel consumption, makes them extremely important in sustainable agriculture. Production of more efficient and more competitive rhizobial strains for use as legume inoculants is a major goal in biotechnology. However, the interactions of introduced rhizobial strains, and the potential for genetic transfer between strains in the environment, are not well understood. Rhizobia are unusual among bacteria in that they have large and complex genomes that usually consist of one chromosome and several very large extrachromosomal genetic elements known as plasmids. The plasmids tend to be very stable, and some of them exhibit properties intermediate between those expected of a plasmid and those of a chromosome. This proposal will focus on the plasmids of