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

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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.