Lipid components from 12 nonpathogenic Mycobacterium species were analysed. A novel cyclic C(35)-terpene, named heptaprenylcycline , was obtained from 3 species, while octahydroheptaprenol , which has 3 Z-double bonds, was obtained from 6 species. The amounts of and in the cultured cells increased after the 4- to 6-d stationary phase. The yield of was considerably greater at a higher temperature of 37 degrees C than at an optimal temperature of 28 degrees C, while that of remained unchanged at all temperatures. A feeding experiment with d-[1-(13)C]glucose revealed that was produced via isopentenyl diphosphate, which is a metabolite of glycolysis and the methylerythritol phosphate pathway. The conversion of octahydroheptaprenyl diphosphate to was successful by using the cell-free extracts of M. chlorophenolicum, demonstrating that is the biosynthetic intermediate of . This is the first example of the biosynthesis of a natural terpene via the cyclisation of a linear C(35)-isoprenoid. The substrate for C(35)-terpene cyclase has Z-type prenyl moieties; however, terpene cyclases usually employ E-type isoprenoids. The gene encoding the terpene cyclase that cyclises prenyl diphosphate containing Z-double bonds as the natural substrate has not yet been detected. Despite a careful search using the FASTA3 program, we could not detect any gene that is homologous to the known diphosphate-triggered type of mono-, sesqui- and diterpene cyclases in the genome of M. vanbaalenii, the DNA sequence of which has recently been elucidated. This suggests that a novel type of terpene cyclase might exist in the nonpathogenic Mycobacterium species.