A novel biosynthetic pathway for the unique volatile 'sodorifen' of Serratia odorifera 4Rx13

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Volatiles are well-established inter and intra species communication and recognition signals. Only recently it was demonstrated that beside other organisms also bacteria emit a wealth of volatiles. Particularly rich is the blend of Serratia odorifera 4Rx13 (up to 100 volatiles). The structure of the dominant compound (C16H32, 1,2,4,5,6,7,8-heptamethyl-3-methylenebicyclo[3.2.1]oct-6-ene, named sodorifen) is unique and novel to science. The polymethylated structure is extremely unusual and the biosynthetic pathway is completely unknown and presently not predictable. The following strategies will be performed to elucidate the biosynthetic pathway of this new natural compound: i) Feeding experiments indicated met, thr, ala, his, lys, or succinate and fumarate as favored substrates for the biosynthesis of sodorifen. Subsequently 13Camino acids and 13C-succinate, and NMR will be performed to predict the composition of sodorifen and the underlying reactions. ii) Proteomes of sodorifen emitting and non-emitting Serratia species should allow the detection of sodorifen biosynthesis enzymes. iii) The genome of S. odorifera 4Rx13 was completely sequenced to support the identification of putative biosynthesis genes. Newly isolated genes will be used a) to functionally characterize them via knockout mutants and b) to search for the origin of the biosynthetic pathway in metagenomic libraries. Ultimately research concerning the biological/ecological relevance of sodorifen will be initiated.