What are the determinants of plant-microbe symbioses?

Professor, Microbiology

My long-term research goal is to elucidate the molecular, cellular, and ecological events that have major impact on development of beneficial plant-microbe symbioses. A major focus has been on the structures, production, and physiological functions of various signal molecules that enable the soil bacterium, Rhizobium, to communicate with its legume host and trigger development of the N2-fixing root nodule symbiosis. A second line of research has focused on identifying new ecological niches for rhizobia. Three unique niches recently identified for certain rhizobia are the development of the root nodule symbiosis with the extremely drought-tolerant legume Hedysarum coronarium, the stem/root nodule symbiosis with the tropical aquatic legume Neptunia natans, and a beneficial endophytic association within the root interior of rice grown in fields that have been rotated with legumes since antiquity. A third line of research is to define the dynamic community ecology of rhizobacteria during the pioneer stage of their root colonization in soil, and to develop a computer-based image analysis system tailored to in situ measurements of microbial diversity and spatial distributions of natural microbial communities.

Selected Publications

Squartini, A., F. Dazzo, S. Casella and M. Nuti. 1993. The root-module symbiosis between Rhizobium hedysari and its drought-tolerant host, Hedysarum coronarium. Symbiosis 15:227-238.

Subba-Rao, N., P. Mateos, D. Baker, H.S. Pankratz, J. Palma, F.B. Dazzo and J. Sprent. 1995. The unique root-nodule symbiosis between Rhizobium and the aquatic legume Neptunia natans. Planta 196:311-320.

Dazzo, F.B., G. Orgambide, S. Philip-Hollingsworth, R. Hollingsworth, K. Ninke and J. Salzwedel. 1996. Modulation of development, growth dynamics, wall crystallinity, and infection sites in white clover root hairs by membrane chitolipooligosaccharides from Rhizobium leguminosarum biovar trifolii. J. Bacteriol. 178:3621-3627.

Yanni, Y.G., R. Rizk, V. Corich, A. Squartini, K. Ninke, S. Philip-Hollingsworth, G. Orgambide, F. de Bruijn, J. Stoltzfus, D. Buckley, T. Schmidt, P. Mateos, J.K. Ladha and F.B. Dazzo. 1997. Natural endophytic association between Rhizobium leguminosarum br. trifolii and rice roots and assessment of its potential to promote rice growth. Plant & Soil 194:99-114.