Improvement of Histidine-producing Strains of Serratia marcescens by Cloning of a Mutant Allele of the Histidine Operon on a Mini-F Plasmid Vector

Abstract

Two hybrid plasmids bearing a mutant allele of the histidine operon of Serratia marcescens on a mini-F plasmid vector were constructed: one was plasmid pSS503 harboring the 4.7-kb EcoRI fragment bearing the initial part of the histidine operon and the other was plasmid pSH368 harboring the 12-kb EcoRI-BamHI fragment bearing the whole histidine operon. Both plasmids increased the activities of ATP-phosphoribosyltransferase (hisG product), histidinol dehydrogenase (hisD product) and histidinol phosphate phosphatase (hisB product) about two-fold, as compared with those observed with the plasmid-free host strain, a histidine-producing strain, L120, of Serratia marcescens. Both plasmids were considerably unstable in the histidine-producing strain, although they were completely stable in the wild-type strain. Strain L120 carrying either pSS503 or pSH 368 produced 42 mg/ml or L-histidine; this productivity was approximately 50% more than that of plasmid-free strain L120. © 1987, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.