Genetics and Biochemistry of the Rhizobium Meliloti Acidic Extracellular Heteropolysaccharide and Its Role in Nodulation: Annual Report for the Period 1 June 1987-31 May 1988

摘要

The symbiotic association of Rhizobium with legumes results in a vital supply of inexpensive nitrogen for the growth of crops such as soybean and alfalfa. In a complex series of events, the bacterial symbiont, Rhizobium, induces the formation of a specialilzed root structure, the nodule. Rhizobium then enters the cells of the nodule and fixes nitrogen. We are interested in an extracellular polysaccharide, produced by Rhizobium, which is required for nodule entry. We have found that R. meliloti mutants which produce the polysaccharide but fail to enter nodules, actually produce an abnormal form of the polysacchardie which lacks succinate. Recently we have discovered a second polysaccharide which can be produced in place of the first polysacchaaride and also satisfy the requirement for nodule entry. We are studying the gentic regulation of the production of the two polysaccharides.