Assistant Research Professor
Ph.D. 1996, National Research Institute for Agricultural Microbiology, St. Petersburg, Russia
The mechanisms of nitrogen fixation have attracted serious study due to their great impact on agriculture and natural ecosystems. The symbiosis between rhizobia and legumes fixes about the same amount of nitrogen worldwide as the chemical fertilizer industry produces. We study the symbiotic association between Sinorhizobium meliloti 1021 and legumes like alfalfa (Medicago sativa) and its diploid model plant relative, Medicago truncatula, as a comprehensive model to study host-microbe interactions. Our main research interests are focused on factors influencing rhizobial symbiotic behavior and nitrogen metabolism in plant-bacterial association.
We have focused our research on understanding rhizobial general nitrogen stress response regulation and the role of GInD uridinyltransferase and uridylyl cleavage enzyme in this pathway. This research incorporates genetic and biochemical analysis of nitrogen stress regulatory cascade. The goal of our research is to understand the structure and the function of GlnD-regulatory cascade, which we have shown plays an important role in bacterial symbiotic behavior.
The ability of S. meliloti to form nitrogen fixing associations with Medicago crops make the bacteria an important part of energy-saving sustainable agricultural practices, especially in marginal and degraded soils. In collaboration with a group in Russia, we have recently obtained a grant from CRDF to study a salt tolerant strain from the Aral Sea region, the site of one of the world’s largest environmental disasters. The aim of this project is to identify genetic determinants of S. meliloti fitness in stress environments, both in symbiotic and free-living conditions.
As for many other bacteria, S. meliloti osmoadaptation depends on the accumulation of potent osmolytes, including glycine-betaine. Recently, we discovered that BetB2 protein, which is a putative betaine aldehyde dehydrogenase, is important in both S. meliloti glycine betaine catabolism and salt resistance. Our current research is focused on identifying the mechanism of action of the BetB2 and understanding its role in S. meliloti general metabolism and osmoprotection.