Poster: Integrated Plant Biology

Abs # 89: Kinetics and macromolecules of attachment in the B. japonicum-soybean symbioses

Presenter:	Jackson, Deneen A., dajjy200@hotmail.com
Authors	Jackson, Deneen A. (A)   Oehrle, Nathan W. (B)   Emerich, David W. (B)
Affiliations:	(A): Long Island University - Brooklyn Campus (B): University of Missouri - Columbia

The interaction between Bradyrhizobium japonicum, a dimorphic soil bacterium and its host plant, soybeans, is beneficial for plant growth. Rhizobium-leguminous plant symbioses result in the formation of nodules on the root of the plant. It is through these nodules that symbiotic nitrogen fixation occurs using nitrogenase, a bacterial enzyme, to convert dinitrogen to ammonia employing 16 ATPs. This process is the major source of nitrogen from the biosphere.

To understand what limits nitrogen fixation and consequently plant growth and development, it is necessary to look closely at the initiation of symbiosis by examining the mechanisms of attachment of B. japonicum to the soybean root. Through in vivo attachment assays where soybean roots were incubated in the presence of B. japonicum for various points in time, we discovered that bacterial attachment to the soybean root hair is a multi-phased process. Initially the bacteria binds to the soybean root loosely and without specificity. Eventually, with the assistance of proteins, tight binding occurs and it is suspected that a cap formation develops where the bacteria accumulate at the attachment site. Using in vitro analysis procedures, we were also able to confirm the presence of a protein believed to be involved in this crucial attachment process.