Properties of Double Mutants of Rhizobium leguminosarum Which Are Defective in the Utilization of Dicarboxylic Acids and Sugars

Abstract

SUMMARY: Rhizobium leguminosarum MNF3201 is a mutant defective in C4 dicarboxylic acid transport (dct). which forms ineffective nodules on pea. The Tn5-induced mutants MNF3041 (ribokinase-negative), MNF3045 (arabinonate dehydratase-negative), MNF3064 (defective in the “Entner-Doudoroff enzymes”) and MNF3070 (pyruvate carboxylase-negative) nodulate peas and fix N2. The carbohydrate-utilization mutations of these strains were each transduced into MNF3201 using phage RL38. The double mutants were defective in the utilization of both C4 dicarboxylic acids and the respective carbohydrates. All the double mutants formed nodules on peas, although these were still ineffective. Thus it appears that R. leguminosarum can use carbon sources other than dicarboxylic acids or common classes of sugars to fuel the nodulation process.