Abstract

Lincomycin, a clinically important lincosamide antibiotic, is primarily produced by Streptomyces lincolnensis. This study demonstrated that fructose supplementation inhibits lincomycin biosynthesis. Gene function analysis and gene knockout experiments revealed that the fructose metabolism regulator FruR negatively regulates lincomycin biosynthesis. Quantitative real-time PCR, electrophoretic mobility shift assays, DNase I footprinting assays, and indigoidine synthase reporter assays demonstrated that FruR specifically binds to sequence -GYCCGAACSTGT-, repressing transcription of the fructose metabolism operon. Additionally, FruR directly suppresses the expression of lincomycin biosynthetic gene lmbA, thereby inhibiting lincomycin production. FruR also modulates the expression of several genes involved in carbon metabolism, including aceE2, glmU, and murQ, thereby influencing carbon flux and cellular growth. Further experiments revealed that FruR also controls genes related to fatty acid synthesis (icmB) and oxidative stress response (sigR), suggesting its broad physiological role. Collectively, these findings position FruR as a pleiotropic regulator linking primary and secondary metabolism, providing new insights into carbon source-dependent regulation of secondary metabolism and identifying potential targets for metabolic engineering to enhance lincomycin production.