Engineering of Primary Carbon Metabolism for Improved Antibiotic Production in Streptomyces lividans

ABSTRACT Deletions were made in Streptomyces lividans in either of two genes (zwf1 and zwf2) encoding isozymes of glucose-6-phosphate dehydrogenase, the first enzyme in the oxidative pentose phosphate pathway (PPP). Each mutation reduced the level of Zwf activity to approximately one-half that observed in the wild-type strain. When the mutants were transformed with multicopy plasmids carrying the pathway-specific transcriptional activator genes for either the actinorhodin (ACT) or undecylprodigiosin (RED) biosynthetic pathway, they produced higher levels of antibiotic than the corresponding wild-type control strains. The presumed lower flux of carbon through the PPP in each of the Δzwf mutants may allow more efficient glucose utilization via glycolysis, resulting in higher levels of antibiotic production. This appears to occur without lowering the concentration of NADPH (the major biochemical product of the oxidative PPP activity) to a level that would limit antibiotic biosynthesis. Consistent with this hypothesis, deletion of the gene (devB) encoding the enzyme that catalyzes the next step in the oxidative PPP (6-phosphogluconolactonase) also resulted in increased antibiotic production. However, deletion of both zwf genes from the devB mutant resulted in reduced levels of ACT and RED production, suggesting that some of the NADPH made by the PPP is utilized, directly or indirectly, for antibiotic biosynthesis. Although applied here to the model antibiotics ACT and RED, such mutations may prove to be useful for improving the yield of commercially important secondary metabolites.

Croonian Lecture - Lethal synthesis

It is hardly necessary for me to refer to my appreciation of the great honour conferred in asking me to give this lecture. It might be thought that the title is more suited to a detective novel and that it was somewhat frivolous for the occasion! Curiously enough I hope that some of the points with which I shall deal to-day will make the path of would-be poisoners somewhat more thorny; and in a way there has been a little of the detective atmosphere about the research. My main theme is the biochemistry and physiology of the poison fluoroacetic acid; this is, as I think, the first instance of ‘lethal synthesis’ in the sense that fluoroacetic acid becomes lethal only when it has been transformed by the action of the tissue enzymes. It is the biochemistry which makes it lethal, the poison being a biochemical product of the tissue which is poisoned.