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Transformation deficient mutants were isolated by nitrosoguanidine mutagenesis. A mutant Tra-12 was defective in the spontaneous development of competence for genetic transformation during culture growth, and showed no activator (competence inducing factor) activity inside or outside of the cells throughout growth. However, Tra-12 exhibited normal competence after the addition of an activator extracted from the wild type strain. This mutant needed a much larger quantity of the activator to develop a saturating level of competence and the induced competence disappeared more rapidly than in the wild type strain.

The promotive effect of biotin (200~500 µg/liter) on l-lysine formation was investigated in Brevibacterium lactofermentum. This effect was observed only when glucose or pyruvate was used as sole carbon source, and accompanied with the specific incorporation of 18CO2 into γ-CH2 group of l-lysine. Brev. lactofermentum AJ 3445 (AECr) could grow on pyruvate medium supplemented with biotin at more than 200 µg/liter, while the same growth was observed with the addition of TCA cycle members or glutamate to pyruvate medium.Phosphoenolpyruvate (PEP) carboxylase deficient mutant derived from AJ 3445 could not grow on glucose as sole carbon source, but on glucose plus 200 µg/liter of biotin. AJ 3445 grown on lactate medium containing 500 µg/liter of biotin and KHCO3 contained the biotin-dependent pyruvate carboxylase.These data suggest that this promotive effect of excess biotin on l-lysine formation may be brought about through the activation of pyruvate carboxylase by biotin.

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.