Fig. 8

Working model for the coordinated control of growth metabolism and butenyl-spinosyn biosynthesis through Fe and Bfr in S. pogona. Fe²⁺ in the environment is absorbed and stored in Bfr in the form of Fe³⁺, which protects cells from iron toxicity followed by release in the form of Fe²⁺ for life activities when needed by cells. Overexpression of bfr enhances the ability of strains to store iron, and promotes oxidative stress response to avoid oxidative damage in order to adapt to high iron concentration environments, affects central carbon metabolism and oxidative phosphorylation to synthesize more short-chain acyl-CoA precursors. Together, these factors promote the biosynthesis of butenyl-spinosyn