9722988 Phillips Soil bacteria have evolved sophisticated mechanisms for coexisting with plant roots. The focus is on the interaction of Rhizobium meliloti and alfalfa. The work is based on the previous detection of a bacterial factor that stimulated root respiration, although the factor is structurally not identical to the known lipo-chitin oligosaccharide signals involved in nodulation. In addition, the factor does not induce roothair curling and its synthesis is not dependent on the presence of roots. The work will characterize this factor and determine its structure. Bacterial mutants which do not synthesize the factor will also be characterized to unravel the biosynthetic pathway. Finally, the purified compound and the bacterial mutant strains will be used to study alterations in root colonization, signaling between the symbiotic partners and plant responses.
