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

在全球范围内，涉及共生根瘤菌的固氮是许多重要粮食作物（如豌豆、扁豆、大豆和鹰嘴豆）氮输入的主要来源。根瘤菌代表了一个极好的模型系统，用于研究基本生物学意义的问题，例如理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宿主植物感染期间。我的研究项目的目的是鉴定和表征豆科根瘤菌在适应不同土壤条件和植物侵染过程中调节包膜组成所需的包膜基因和调控途径。细胞包膜是研究细菌对压力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，我们有兴趣了解r.m leguminosarum如何调节细胞包膜以在环境胁迫下生存，例如干旱引起的干燥。值得注意的是，R. leguminosarum为加拿大大草原上种植的几种重要粮食作物（包括豌豆和扁豆）固定氮，据预测，到2028年，大草原年作物基础的三分之一将是这些脉冲作物。尽管如此，与模型根瘤菌研究物种Sinorhizobium meliloti相比，人们对这种具有重要农业意义的根瘤菌物种知之甚少。更好地了解R. leguminosarum如何调节细胞包膜以在土壤和感染期间存活，可以帮助农业生物技术行业创造出更有效的接种剂，旨在为加拿大农民增加豆类作物产量。此外，加拿大在农业生物技术领域处于全球领先地位，在这项研究中接受培训的学生将掌握分子方法的技能，这些技能受到农业生物技术雇主的追捧，为他们未来在这一不断扩大的领域的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.