The volatiles emitted from cell cultures of myxobacterium Myxococcus xanthus were collected by use of a closed-loop stripping apparatus (CLSA) and analyzed by GC-MS. Two new natural products, (S)-9-methyldecan-3-ol ((S)-1) and 9-methyldecan-3-one (2), were identified and synthesized, together with other aliphatic ketones and alcohols, and terpenes. Biosynthesis of the two main components (S)-1 and 2 was examined in feeding experiments carried out with the wild-type strain DK1622 and two mutant strains JD300 and DK11017, which are impaired in the degradation pathway from leucine to isovaleryl-SCoA. Isovaleryl-SCoA is used as a starter, followed by chain elongation with two malonate units. Subsequent use of methyl malonate and decarboxylation leads to (S)-1 and 2. Furthermore, 3,3-dimethylacrylic acid (DMAA) can be used by the mutant strain to form isovaleryl-SCoA, which corroborates recent data on the detection of a novel variety of the mevalonate pathway giving rise to isovaleryl-SCoA from HMGCoA.