Isolation of pea nodule bacteroids utilizing silica sol (Percoll) density gradient centrifugation

Abstract

Isolation of bacteroids from effective (Fix+) and ineffective (Fix−) pea nodules, inoculated withRhizobium leguminosarum K, were performed by a density gradient centrifugation method using silica sol (Percoll). Only one zone (ρ=1.064–1.072; n-zone) was recognized in the Fix+ nodule which contained typical Y-shaped bacteroids while two zones (n-zone and ρ=1.125–1.145; n'-zone) were obtained from the Fix− nodule. The cells in the n'-zone, which are long rods differed morphologically from free-living cells at any growth phase (ρ=1.108–1.125; f-zone and ρ=1.074–1.078; f'-zone), and differed from Y-shaped bacteroids by cell density. The esterase isozyme pattern of bacteroids in the n-and n'-zones also showed clear differences from that of f-and f'-zone of free-living cells.