Peptidoglycan remodelling during Rhizobium leguminosarum life cycle, from the rhizosphere to the formation of bacteroids

植物的最佳生长是通过与土壤微生物（包括细菌、真菌、单细胞动物和线虫）的复杂相互作用来实现的。豆科植物（豆科植物，如豌豆、黄豆、大豆或扁豆）依靠与一组被称为根瘤菌的细菌进行互利的相互作用（共生）来利用大气中的氮。这种基本的营养物质以气体的形式存在，占地球大气的78%，但植物不能直接利用它来合成细胞成分。因此，根瘤菌对氮的同化是植物生长的一个关键过程，这反过来又支持动物的生命，具有巨大的经济和环境影响。使用人工氮肥有很大的环境成本；它占农业使用的化石燃料的近50%，并导致湖泊、河流和饮用水富营养化，有毒藻类繁殖和生物多样性丧失。植物与根瘤菌的共生涉及一个复杂的分子对话，导致细菌侵入根组织并形成根瘤。在这些根瘤内，根瘤菌形成一种叫做类杆菌的特殊细胞，能够将大气中的氮转化为植物所利用的氨。我们已经确定了一个酶家族，在模式共生体豆科根瘤菌的生命周期中差异表达，对根瘤中细菌的生存能力至关重要。本研究的目的是研究这组重要的蛋白质，以了解细菌细胞包膜的重塑如何促进豌豆和豆类的共生。这项工作是为可持续农业设计根瘤菌的重要一步。

Optimal plant growth is achieved through complex interactions with soil microorganisms including bacteria, fungi, single celled animals, and nematodes. Plants belonging to the family of Fabaceae (legumes such as peas, beans, soybeans, or lentils) rely on a mutually beneficial interaction (symbiosis) with a group of bacteria called rhizobia to utilise atmospheric nitrogen. This basic nutrient is present as a gas that makes up 78% of Earth's atmosphere but cannot be used directly by plants for the synthesis of their cellular constituents. Assimilation of nitrogen by rhizobia is therefore a critical process for plant growth, which in turn supports animal life, with a tremendous economic and environmental impact. The use of artificial nitrogen fertilisers has a major environmental cost; it accounts for nearly 50% of the fossil fuel used in agriculture and leads to eutrophication of lakes, rivers and drinking water, toxic algal blooms, and biodiversity loss. The plant-rhizobia symbiosis involves a complex molecular dialog that leads to the bacterial invasion of root tissues and the formation of root nodules. Inside these nodules, rhizobia form specialised cells called bacteroids able to transform atmospheric nitrogen into ammonia used by plants. We have identified a family of enzymes that are differentially expressed during the life cycle of the model symbiont Rhizobium leguminosarum and essential for the viability of bacteria in the nodule. The purpose of this research is to study this group of important proteins to understand how the remodelling of the bacterial cell envelope contributes to symbiosis in peas and beans. This work is an important step to engineer rhizobia for sustainable agriculture.