Quality and rate of extracellular polysaccharides produced by Rhizobium meliloti and their inducing effect on polygalacturonase production in legume roots as derived from the presence of extrachromosomal DNA.

The ability of extracellular polysaccharides of different strains of Rhizobium meliloti to induce the production of polygalacturonase by roots of Medicago sativa seedlings has been studied. Some strains showed a high inducing activity while those derived from them, after treatment with acridine orange and in which extrachromosomal DNA was absent, did not show this character. A comparative study of polysaccharide production and preliminary studies on the chemical composition of the active fractions obtained after Sephadex G-25 filtration indicated that the monomers which form the active fractions are qualitatively and quantitatively different according to their origin.