EFFECT OF GLUCOSE ON AGARASE OVERPRODUCTION BY STREPTOMYCES

The Streptomyces coelicolor dagA gene, coding for an extracellular aga rase, has been propagated on a multicopy plasmid in S. coelicolor A3(2 ), the natural agarase producer strain and in S. lividans TK21, a clos ely related, nonproducer strain. The effect of the carbon source on th e production of agarase by both strains, upon cultivation in liquid me dium, revealed that the glucose repression affected the synthesis of a garase at the level of secretion, rather than at the level of transcri ption. In the presence of glucose, the pre-agarase was degraded intrac ellularly and the overall secretion of proteases decreased considerabl y in both strains, suggesting a negative regulatory role for glucose i n the overall secretion in Streptomyces.