Norleucine accumulation by a norleucine-resistant mutant of Serratia marcescens

A norleucine-resistant mutant was derived from an isoleucine-valine auxotroph of a leucine accumulator of Serratia marcescens. The norleucine-resistant mutant could accumulate norleucine from norvaline in the medium without the addition of methionine, which antagonized norleucine. This mutant constitutively formed homoserine-O-transsuccinylase.