Isolation of Bacteria, Transforming Bacteria, and Bacteroids from Soybean Nodules

Abstract

Postnuclei supernatant soybean (Glycine max cv. Chippewa 64) nodule [Rhizobium] homogenate was fractionated by stepwise sucrose density gradient centrifugation into supernatant, endoplasmic reticulum and mitochondria, and 3 distinct bands with 1.22, 1.25 and 1.27 g/cm3 of peak density. Based on their enzymic activities, composition of electron transport components and ultrastructural characteristics, the lightest band appears to be the mature bacteroids; the intermediate band the transforming bacteria; and the heaviest, the bacteria. The isolation procedure separates nodule symbionts into different functional and developmental fractions, and it may be a valuable tool for studies involving development, regulation and senescence of bacteroids in the nodule.