Anaerobic Degradation of Bicyclic Monoterpenes in Castellaniella defragrans
Department of Microbiology, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany
Department of Symbiosis, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany
Pharmaceutical Biotechnology, University Greifswald, Felix-Hausdorff-Straße, 17489 Greifswald, Germany
Author to whom correspondence should be addressed.
Metabolites 2018, 8(1), 12; https://doi.org/10.3390/metabo8010012
Received: 23 January 2018 / Revised: 23 January 2018 / Accepted: 2 February 2018 / Published: 7 February 2018
The microbial degradation pathways of bicyclic monoterpenes contain unknown enzymes for carbon–carbon cleavages. Such enzymes may also be present in the betaproteobacterium Castellaniella defragrans, a model organism to study the anaerobic monoterpene degradation. In this study, a deletion mutant strain missing the first enzyme of the monocyclic monoterpene pathway transformed cometabolically the bicyclics sabinene, 3-carene and α-pinene into several monocyclic monoterpenes and traces of cyclic monoterpene alcohols. Proteomes of cells grown on bicyclic monoterpenes resembled the proteomes of cells grown on monocyclic monoterpenes. Many transposon mutants unable to grow on bicyclic monoterpenes contained inactivated genes of the monocyclic monoterpene pathway. These observations suggest that the monocyclic degradation pathway is used to metabolize bicyclic monoterpenes. The initial step in the degradation is a decyclization (ring-opening) reaction yielding monocyclic monoterpenes, which can be considered as a reverse reaction of the olefin cyclization of polyenes.