Flow-microfluorometric analysis of bacteroids fractionated from alfalfa and soybean nodules by buoyant density sedimentation

Abstract The cell size and DNA and protein content of bacteroids fractionated from alfalfa and soybean nodules by buoyant density sedimentation were examined by laser flow-microfluorometry. In alfalfa nodules, these parameters were inversely related to bacteroid density. The bacteroids which sedimented at the highest density ( p = 1.268 ) resembled free-living Rhizobium meliloti in cell size and protein content but averaged slightly higher in DNA content. The bacteroids which sedimented at the lowest density ( p = 1.224 ) averaged larger in size and contained significantly more DNA and protein then free-living R. meliloti . Despite the difference in density, bacteroid fractions from soybean nodules and free-living Rhizobium japonicum were similar in all measured parameters.