Comparison of nodulating and non-nodulating strains ofRhizobium trifolii

Summary A non-nodulating mutant ofRhizobium trifolii and its nodulating parent were examined for possible dissimilarities in their extracellular polysaccharides, antigen composition and ability to grow on the roots ofTrifolium pratense. A major distinction between the two organisms was observed to be the inability of the non-nodulating strain to grow in the root-tip region ofT. pratense. A small quantitative difference in antigen composition but no significant qualitative or quantitative differences in the extracellular polysaccharides of the two bacteria were noted. The non-nodulating rhizobium could not be induced to nodulate seedlings ofT. pratense either in the presence of nodulating rhizobia or after ultraviolet treatment of the bacteria.