Decoding the regulatory role of AmiC in amicoumacins production through transcriptomics and metabolic profiling in Bacillus subtilis fmb60.

Amicoumacins are a group of NRPS-PKS antibiotics produced by Bacillus species that exhibit broad-spectrum antibacterial, anti-inflammatory, and anticancer activities. Despite their promising pharmacological potential, the regulatory mechanisms underlying their biosynthesis remain largely unexplored, hindering the development of rational approaches for yield enhancement. In this study, we investigated the regulatory function of the amiC gene in the biosynthesis of amicoumacin by Bacillus subtilis fmb60. An amiC-overexpressing strain was constructed and displayed a significant increase in total amicoumacin production, which was correlated with larger inhibition zones against both Staphylococcus aureus and Escherichia coli. Conversely, deletion of amiC led to a substantial decrease in amicoumacin yield, to only 23.5% of the wild-type level (a 4.26-fold reduction). Metabolomic profiling further confirmed that AmiC functions as a positive regulator of multiple amicoumacin derivatives. Transcriptomic analysis of the knockout strain identified 68 differentially expressed genes, with KEGG enrichment indicating significant involvement of flagellar assembly, bacterial chemotaxis, and two-component system pathways. Mechanistic insights further suggested that loss of amiC perturbs cellular metabolism by enhancing chemotaxis and regulatory signaling, thereby diverting metabolic flux away from secondary metabolite biosynthesis. Collectively, these findings demonstrate that amiC act as a key positive regulator of amicoumacin biosynthesis and represents a promising target for metabolic engineering to improve antibiotic production.