Microorganisms degrading cyclic and short-chain alkanes under anoxic conditions

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Propane and butane are important constituents of natural gas and crude oil. Propane and butane reach the biosphere through a worldwide estimate of 10,000 natural oil and gas seeps, or as a result of industrial activities. They play a significant role in carbon cycling at such seepage sites, serving as substrates for aerobic and anaerobic microorganisms. While the aerobic degradation of propane and butane has been intensively studied, relatively little is known of the degradation of these alkanes under anoxic conditions. Strain BuS5 is up to now the only pure culture that can degrade propane and butane under anoxic conditions. Strain BuS5 is a mesophilic, sulphate-reducing bacterium, phylogenetically affiliated with the Desulfosarcina-Desulfococcus group of the Deltaproteobacteria. Physiological tests conducted so far have shown that it can use only propane and n-butane as growth substrates. The present project aims at obtaining a deeper understanding of the anaerobic degradation of propane and n-butane using Strain BuS5 as a model organism. The main objectives are (a) annotation and analysis of the genome of Strain BuS5 with a major focus on the alkane activation/degradation enzymes/pathways; the genome will be available through a project by F. Musat and S. Sievert accepted for funding at the Joint Genome Institute (JGI); (b) proteomic analyses of Strain BuS5 grown with short-chain alkanes; and (c) enzymatic studies aiming at the purification and characterization of the propane- and butane-activating enzyme.