Inhibition of nodGene Expression in Bradyrhizobium japonicum by Organic Acids. Joyce Pui-yee Yuen. Center for Legume Research, Departments of Microbiology and Ecology and Evolutionary Biology, M409 Walters Life Science Building, University of Tennessee, Knoxville 37996-0845 U.S.A. Gary Stacey. Center for Legume Research, Departments of Microbiology and Ecology and Evolutionary Biology, M409 Walters Life Science Building, University of Tennessee, Knoxville 37996-0845 U.S.A. MPMI 9:424-428. Accepted 21 February 1996. Copyright 1996 The American Phytopathological Society.

Significant inhibition of nodD1 and nodY gene expression in Bradyrhizobium japonicum occurred when specific organic acids (i.e., acetate, fumarate, L-malate, succinate, or (-ketoglutarate) were added. Gene expression was inhibited by 91% when acetate and L-malate were added together. Since organic acids are thought to be the primary carbon sources used by rhizobia in planta, these results suggest a mechanism by which nod gene expression can be inhibited in bacteroids.