9410840 Margolin, William Nitrogen-fixing nodules on leguminous plants are formed by controlled invasion and symbiosis by Rhizobium species. The bacteria enter the plant cell cytoplasm and differentiate into morphologically distinct, non dividing bacteroids, capable of fixing nitrogen. The arrest of their cell cycle is not due to space limitation or nutrient deprivation. This award is a starter grant based on Dr. Margolin's work as an NSF Plant Postdoctoral Fellow. The research is a continuation of his initial genetic studies of Rhizobium cell division. A gene called ftsZ is being studied as it appears to be a major control point for regulation of the bacterial cell cycle. In addition, immunological and microscopic analysis of the branching and differentiation process occurring in the bacterium is being initiated. %%% The study of cell cycle regulation in Rhizobia should provide a greater understanding of the symbiosis between the bacterium and leguminous plants, and be the groundwork for determining the mechanism of control of invading bacteria by a host plant. ***
