Investigating cell envelope structure and function in the plant symbiont rhizobium leguminosarum

在全球范围内，共生根瘤菌的固氮是许多重要粮食作物的主要氮素输入来源，如豌豆、小扁豆、大豆和鹰嘴豆。根瘤菌代表了一个很好的模型系统，用于研究具有基本生物学意义的问题，例如了解细胞适应不同条件所需的分子机制，无论是在土壤中还是在寄主植物感染期间。我的研究计划的目标是确定和表征豆根瘤菌在适应不同的土壤条件和植物侵染过程中调节细胞膜成分所需的细胞膜基因和调控途径。细胞被膜是研究细菌对胁迫的适应性反应的一个有趣的目标，因为它是抵御外部压力的第一道防线，保持其完整性是在外部环境和宿主中生存的先决条件。例如，我们感兴趣的是了解豆腐病菌如何调节细胞膜以适应环境胁迫，如干旱诱导的干燥。值得注意的是，豆类根瘤杆菌固定了加拿大大草原上种植的几种重要粮食作物的氮素，包括豌豆和小扁豆，预测到2028年，草原上每年三分之一的作物基地将在这些豆类作物中。尽管如此，与模式根瘤菌研究种紫花苜蓿相比，人们对这种在农业上具有重要意义的根瘤菌知之甚少。更好地了解豆类根霉如何调节细胞膜在土壤中和感染期间生存，可以帮助农业生物技术行业创造更有效的接种剂，旨在增加加拿大农民的豆类作物产量。此外，加拿大在农业生物技术领域处于全球领先地位，在这项研究期间接受培训的学生将发展以分子为基础的方法技能，这些技能受到农业生物技术雇主的追捧，为他们未来在这个不断扩大的部门就业奠定了良好的基础。

Globally, nitrogen fixation involving symbiotic rhizobia is the major source of nitrogen input for many important food crops, such as peas, lentils, soybeans and chickpeas. The rhizobia represent an excellent model system for investigating questions of fundamental biological significance, such as understanding the molecular mechanisms required for a cell to adapt to diverse conditions, both in the soil and during infection of a host plant. The objective of my research program is to identify and characterize cell envelope genes and regulatory pathways that are required to modulate the composition of the cell envelope during Rhizobium leguminosarum's adaptation to varying soil conditions, and during plant infection. The cell envelope is an interesting target for studying bacterial adaptive responses to stress since it is the first line of defense against external stresses and maintaining its integrity is a prerequisite for survival within the external environment as well as a host. For example, we are interested in understanding of how R. leguminosarum modulates the cell envelope to survive environmental stresses, such as drought induced desiccation. Notably, R. leguminosarum fixes nitrogen for several important food crops that are grown on the Canadian prairies including peas, and lentils, and predictions estimate that by 2028, 1/3 of the annual crop base in the prairies will be in these pulse crops. In spite of this, relatively little is known about this agriculturally important Rhizobium species compared to the model rhizobial study species Sinorhizobium meliloti. A better understanding of how R. leguminosarum modulates the cell envelope to survive in soil and during infection can help agri-biotech industries create more effective inoculants designed to increase legume crop production for Canadian farmers. Furthermore, Canada is a global leader in the agricultural biotechnology sector and the students trained during this research will develop skills in molecular based approaches that are sought after by agri-biotech employers, positioning them well for future employment in this expanding sector.