Parallel Evolution of a Drimenol Biosynthetic Gene Cluster Unique to Marine Bacteria

Natural bacterial communities represent a rich resource for the discovery of enzymes and natural compounds including terpenoids. However, the biosynthetic potential of marine bacteria remains poorly explored due to limitations in studying fastidious microorganisms. In a recent study, we discovered unusual haloacid dehalogenase (HAD)-like drimenol synthases (DMSs) of marine bacterial origin, including Aquimarina spongiae AsDMS and Flavivirga eckloniae FeDMS, which produce drimenol in vitro . In the present study, we conducted an in vivo investigation of the biosynthesis of this drimane-type sesquiterpene in marine bacteria. To verify drimenol accumulation in cultures of F. eckloniae , we mined the drimenol biosynthetic genes encoded in the F. eckloniae genome and found a putative AraC family transcriptional regulator in the drimenol gene cluster. Upon the addition of arabinose, we observed drimenol biosynthesis in F. eckloniae , demonstrating the importance of genomics-driven strategies in investigating natural products. Syntenic comparisons of drimenol gene clusters across bacteria revealed the unique evolution of drimenol biosynthesis in marine bacteria. Moreover, the distinct nature of drimenol pathways and relevant enzymes in bacteria compared to those in plants and fungi suggests parallel evolution. Remarkably, we describe two individual proteins from Sorangium cellulosum , HAD and terpene synthase with β domain architecture, similar to HAD-like and terpene synthase β domains of AsDMS, respectively, suggesting the fusion of monodomain proteins during the evolution of bacterial bifunctional DMSs. Our findings shed light on the evolutionary trajectory of the drimenol gene cluster unique to marine bacteria, while also demonstrating the new bacterial mono-β-domain sesquiterpene synthase.