Non-C 5 -units terpenoids (norisoprenoids) with an acetonyl group are widely distributed in nature.H owever, studies on the biosynthesis of norisoprenoids are scarce.Now, the C 33 norisoprenoid, (all-E)-farnesylfarnesylacetone,w as identified from Bacillus spp.and it was elucidated for the first time that superoxidem ediates the cleavage of menaquinones (vitamin K) to form norisoprenoids in saponification treatment. From in vivo experiments using gene-disrupted Bacillus subtilis strains targeted for enzymes responsible for menaquinone biosynthesis and for superoxided ismutase,i tw as suggested that the non-enzymatic cleavage (autoxidation) of menaquinone with superoxide resulted in norisoprenoid synthesis in Bacillus cells.F urthermore,t he bioactive norisoprenoids,farnesylacetone and phytone,were produced in Bacillus cells by this novel synthesis system.