To test our hypothesis that MicA is capable of synthesizing a non-flexible eunicellane scaffold, we first examined the activity by simultaneously expressing MicA and MKI4 (ref. 23), a two-step kinase system efficiently producing geranylgeranyl diphosphate (GGPP) , in Escherichia coli. This resulted in the generation of two major peaks (85% + 10%), along with several minor peaks (totally 5%) (Fig. ) at retention time 25~35 min, similar to previously reported diterpenes . Moreover, identical peaks were observed by replacing Bnd3 in MKI4 (Fig. , Supplementary Figure ) with MicE, a hypothesized polyprenyl diphosphate synthase (Fig. ), indicating the capability of synthesizing a diterpenoid by the targeted gene cluster. Subsequently, we purified the major products, 1 and 2, via a large-scale fermentation (Methods) and analyzed them with GC-MS, 1D, and 2D NMR, showing consistent patterns to a new eunicellane (1, we named it microeunicellene) and a known cembrane scaffolds (2, pinacene ) (see Supplementary Information for detailed structural elucidation). The minor products are inseparable under our laboratory conditions. However, we annotated them as cembrene isomers by GC-MS analysis and comparison with the NIST database (Supplementary Figure ).