Identification and characterisation of the gene cluster governing biosynthesis of the anti-mycobacterial antibiotic acidomycin

Acidomycin is an anti-mycobacterial antibiotic with a unique mode of action, targeting the biotin biosynthesis pathway. Despite being highly active against mycobacteria in vitro, its development as an anti-tubercular agent has been hindered due to suboptimal pharmacokinetics. Engineering of the acidomycin biosynthesis may yield new analogues with improved pharmacological properties. Here, we describe the identification of the acidomycin biosynthetic gene cluster (BGC) in a Streptomyces bacterium isolated from the rhizosphere of Edelweiss. Notably, the acidomycin BGC is located in proximity to the genes for the biosynthesis of stravidins, secondary metabolites targeting a different enzyme in the biotin biosynthesis pathway, and two genes for streptavidins, proteins that strongly bind and sequester biotin. The identity of the acidomycin BGC was confirmed via both gene knock-out and heterologous expression, which suggested that the fatty acid required for the formation of acidomycin's acyl chain is most likely scavenged from the biotin biosynthesis pathway. CRISPR/Cas9-assisted knock-out of the cytochrome P450-encoding gene in the acidomycin BGC resulted in a significant decrease in its yield but did not abrogate the biosynthesis completely.