Enhancing Secondary Metabolite Production in Actinobacteria Through Over-Expression of a Medium-Sized SARP Regulator

Natural products hold immense therapeutic potential, yet they remain underexplored due to challenges in activating or producing them in laboratory settings. Here, we investigate the regulatory capabilities of a new medium-sized Streptomyces Antibiotic Regulator Protein (SARP), Fzm_SARP, in comparison to the well-characterized small SARP, RedD, across 18 diverse actinobacterial strains. In addition to the conserved DNA-binding domains typical of SARP regulators, the medium-sized Fzm_SARP also contains an additional NTPase domain. Our study revealed that 327 of the 422 metabolites (77%) detected in 18 wild-type actinobacterial strains were up-regulated in the SARP over-expressing strains. Among these 422 metabolites, 55% were up-regulated in the two SARP over-expressing strains whereas 15% and 7% were specifically up-regulated in the RedD and Fzm_SARP over-expressing strains, respectively. Interestingly, 244 metabolites not previously detected in the wild-type strains were detected in the two SARP over-expressing strains, resulting in a 58% increase from 422 to 666 metabolites. 36% of these new 244 metabolites were up-regulated in the two SARP over-expressing strains whereas 37% and 27% of these metabolites were specifically up-regulated in the RedD and Fzm_SARP over-expressing strains, respectively. These regulator-specific metabolites also give rise to distinct bioactivity profiles observed for each SARP. Overall, these findings expand our understanding of SARP family regulators and offer valuable insights for future research and applications in microbial biotechnology and secondary metabolite production.