RHIZOBIUM-LEGUMINOSARUM BIOVAR TRIFOLII MUTANTS ALTERED IN SURFACE-STRUCTURES THAT ARE DEFECTIVE IN NODULATION OR NITROGEN-FIXATION

Complex characteristics of symbiotic mutants of Rhizobium legwninosaru m bv. trifolii strain 24 are presented. The mutants were divided into two main classes. The first group of mutants was defective in exopolys accharide (EPS) synthesis (Exo-) and formed non-fixing nodules on clov er. The second group of mutants was changed in lipopolysaccharide (LPS ) components and was not able to induce nodules on plants. In comparis on to wild type strain 24, we did not observe essential differences in plasmid, phage and LPS patterns in the Exo- mutants. On the other han d, the second group of symbiotic mutants revealed significant changes in respect of the above characters. The large alteration both in LPS c omposition and electrophoretic patterns may suggest that these non-nod ulating mutants produce LPS of an another type (LPS II). The synthesis of LPS II causes a change in the response to surface active component s, including the flavonoids.