FIGURE 3. Anaerobic activation reactions of propane suggested by identified metabolites.

Whereas previous studies on the anaerobic degradation of alkanes suggested their activation (by homolytic C-H-bond cleavage) exclusively at a secondary carbon atom^{5, 6, 15}, the new cultures obviously activate propane at both the secondary and the primary carbon (marked with asterisks). The products from reaction with fumarate, isopropylsuccinate and n-propylsuccinate were identified by chemical analyses including authentic standards (Supplementary Fig. 6). Subsequent reactions are suggested according to degradation schemes of other alkanes (for details see ref. 5 and Supplementary Fig. 7) and identified fatty acids (see text and Supplementary Table 4).