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

挥发物是物种间和物种内广泛存在的交流和识别信号。直到最近才证明，除了其他生物外，细菌也会释放出大量的挥发物。气味沙雷氏菌4Rx13的混合物(多达100种挥发物)尤其丰富。优势化合物(C16H32，1，2，4，5，6，7，8-heptamethyl-3-methylenebicyclo[3.2.1]oct-6-ene，命名为Sodorifen)的结构在科学上是独一无二的。这种多甲基化结构非常不寻常，生物合成途径完全未知，目前也无法预测。将采用以下策略来阐明这种新的天然化合物的生物合成途径：i)喂养实验表明Met、Thr、Ala、His、Lys或琥珀酸和富马酸是Sodorifen生物合成的有利底物。随后，将通过13Camino酸和13C-琥珀酸，以及核磁共振来预测Sodorifen的组成和潜在的反应。2)产Sodorifen和不产Sodorifen沙雷氏菌的蛋白质组应允许检测Sodorifen生物合成酶。Iii)对香菇4Rx13的基因组进行了全序列测定，为鉴定可能的生物合成基因奠定了基础。新分离的基因将被用来a)通过敲除突变体来表征它们的功能，以及b)在元基因组文库中寻找生物合成途径的起源。最终，将启动关于索多利芬的生物学/生态相关性的研究。

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.