9603762 Emerich Symbiotic nitrogen fixation is the predominate pathway for conversion of atmospheric nitrogen into biologically usable forms. While we know the rhizobial genes that make up the machinery for nitrogen fixation, the process is complicated by the symbiotic relationship that must first be established between the Rhizobia and the plant that leads to the development of plant root nodules. The initial step of how contact is made between the bacteria and plant cells is in the focus of the proposed work. The overall objective of the work is to elucidate the role of surface polysaccharides particularly extracellular polysaccharides in the infection/nodulation process of determinate legumes. Although all types of polysaccharides will be considered, the proposal will focus on the role of extracellular polysaccharides in the Bradyrhizobium japonicum-soybean symbiosis. Objectives include the search for genes that encode enzymes for polysaccharide synthesis, determination of the function of a reading frame that is involved in the synthesis pathway, determination of the nodulation capacity of mutant bacteria, and complementation tests. The research will lead to a better understanding of plant-microbe communication/interaction.
