SPP 1319:  Biological Transformations of Hydrocarbons in the Absence of Oxygen

Mechanistic Inverstigations on Hydrocarbon Degradation in Anaerobic Bacteria

Hydrocarbons are the main component of crude oils and various petrochemical products. Their biological degradation in oxygen-free habitat, as marine sediments or petroleum reservoirs, play an important role in the global carbon cycle. During the last 25 years numerous strains of denitrifying and sulfate-reducing bacteria have been isolated and characterized, which are able to use hydrocarbons as sole carbon and energy source. Based on the identification of metabolites, and on results from studies using isotope-labelled substances, our aim is to decipher degradation pathways leading to complete oxidation of selected hydrocarbons to carbon dioxide by those bacteria. The results obtained for individual strains are matched to genomic and proteomic data generated by our cooperation partners (working group of R. Rabus, ICBM).

In frame of the on-going project we already deciphered the reaction mechanism and the stereochemistry of n-alkane activation by addition of fumarate in the denitrifying strain HxN1 (Jarling et al. 2012). Further, we were able to demonstrate that the activation of alkyl-substituted toluenes, e.g. . p-cymene (4-isopropyl toluene), is achieved in different  bacterial strains, either by hydroxylation of the benzylic methyl group or by addition to fumarate (Strijkstra et al. 2014). Recently, we investigated in vivo the substrate spectrum of hydrocarbon-activating enzymes in numerous anaerobic bacterial strains. We discovered their potential to transform an unexpected wide range of hydrocarbons. Although, these organisms were not able to completely oxidize the majority of the substrates.  Other research in frame of this project will contribute to a better understanding of biogeochemical mechanisms of anaerobic biological hydrocarbon degradation.

Jarling R, Sadeghi M, Drozdowska M, Lahme S, Buckel W, Rabus R, Widdel F, Golding BT, Wilkes H (2012) Stereochemical investigations reveal the mechanism of the bacterial activation of n-alkanes without oxygen. Angewandte Chemie Int. Ed. 51: 1334-1338

Jarling R, Kühner S, Basílio Janke E, Gruner A, Drozdowska M, Golding BT, Rabus R, Wilkes H (2015) Versatile transformations of hydrocarbons in anaerobic bacteria: substrate ranges and regio- and stereochemistry of activation reactions. Frontiers in Microbiology 6: Article 880

Strijkstra A, Trautwein K, Jarling R, Wöhlbrand L, Dörries M, Reinhardt R, Drozdowska M, Golding BT, Wilkes H, Rabus R (2014) Anaerobic activation of p-cymene in denitrifying betaproteobacteria: methyl group hydroxylation versus addition to fumarate. Applied and Environmental Microbiology 80: 7592-7603