Volatile terpenes from actinomycetes: a biosynthetic study correlating chemical analyses to genome data

The volatile terpenes of 24 actinomycetes whose genomes have been sequenced (or are currently being sequenced) were collected by use of a closed-loop stripping apparatus and identified by GC/MS. The analytical data were compared against a phylogenetic analysis of all 192 currently available sequences of bacterial terpene cyclases (excluding geosmin and 2-methylisoborneol synthases). In addition to the several groups of terpenes with known biosynthetic origin, selinadienes were identified as a large group of biosynthetically related sesquiterpenes that are produced by several streptomycetes. The detection of a large number of previously unrecognised side products of known terpene cyclases proved to be particularly important for an in depth understanding of biosynthetic pathways to known terpenes in actinomycetes. Interpretation of the chemical analytical data in the context of the phylogenetic tree of bacterial terpene cyclases pointed to the function of three new enzymes: (E)-β-caryophyllene synthase, selina-3,7(11)-diene synthase and aristolochene synthase.