A Succinate Dehydrogenase-deficient Mutant ofAgrobacterium tumefaciens

A mutant of Agrobacterium tumefaciens was isolated by treatment with N-methyl-N′-nitro-N-nitrosoguanidine as selective markers of succinate-negative and glucose-positive. This succinate-negative mutant was found unable to grow on pyruvate or any intermediate of the tricarboxylic acid cycle as the sole carbon source but able to grow on hexoses. Comparison of biochemical properties of wild-type and mutant strains demonstrated a very low level of succinate dehydrogenase activity in the mutant strain. Reverse mutation from succinate-negative to succinate-positive spontaneously occurred at a frequency of about 10−9. All strains of the revertant isolated recovered their activity of succinate dehydrogenase approximately to the level of the wild-type strain. Thus we presumed that the deficiency of succinate dehydrogenase in this mutant gave a pleiotropic effect on the ability to grow on tricarboxylic acid cycle intermediates.