In this study we investigated the cometabolic oxidation of six cyclic ethers by alkane-grown Mycobacterium vaccae JOB5. These ethers include, among others, tetrahydrofuran (THF), 1,4-dioxane (14D), 1,3-dioxolane (13DO), and tetrahydropyran (THP). Cells grown on propane, n-butane, n-pentane, isobutane, or isopentane oxidized all six ethers. Ether-degrading activity was inhibited by acetylene in alkane-grown cells and was largely absent from cells grown on dextrose-containing media. Propane competitively inhibited THF oxidation. γ-Butyrolactone (γBL) accumulated and was also further oxidized during THF oxidation by propane-grown cells. In contrast, no products were detected during 14D oxidation. Propane-grown cells also rapidly oxidized 3-hydroxytertrahydrofuran and exhibited strong hemiacetal-oxidizing activity in an assay following methyl formate production from mixtures of methanol and formaldehyde. These observations suggest γBL is likely generated during THF oxidation through further oxidation of 2-hydroxytetrahydrofuran. Limited growth of strain JOB5 was supported by several cyclic ethers and the corresponding lactones and diols potentially derived from these compounds. However, strain JOB5 grew more readily on 4-hydroxybutyrate, the product of γBL hydrolysis. The ability of strain JOB5 to productively assimilate THF-derived metabolites during growth on n-alkanes was examined in carbon-limited batch cultures. Relative to C-limited growth on n-pentane alone, culture growth increased up to twofold in the presence of THF while no stimulation of growth was observed in comparable experiments conducted with n-pentane and 14D. Our results are discussed in terms of their significance to our understanding of cyclic ether cometabolism and their potential impact on approaches for cyclic ether biodegradation in the environment. © 2013 Wiley Periodicals, Inc.