Journal Article

Anaerobic oxidation of short-chain hydrocarbons by marine sulphate-reducing bacteria

Kniemeyer, Olaf, Musat, Florin, Knittel, Katrin, Bolm, Carsten, Wilkes, Heinz, Michaelis, Walter, Widdel, Friedrich, Joye, Samantha B., Sievert, Stefan M., Classen, Arno, Blumenberg, Martin

2007

Overview

Natural gas guzzlers There has been an increasing interest in organisms thriving at marine gas seeps, in particular microbes that utilize methane. Surprisingly, there seems to have been comparatively little work done on the fate of the other abundant hydrocarbons in natural gases — ethane, propane and butane. Now sediments collected from hydrocarbon seep areas in the Gulf of Mexico and the Gulf of California have yielded microbial cultures that utilize propane and butane under anoxic conditions similar to those prevailing in gas reservoirs. These biochemically unusual bacteria may be responsible for the observed alteration of gases in seeps and other gas reservoirs. Ethane, propane and butane are constituents of natural gas in anoxic marine sediments. The first microbial isolate belonging to the sulphate-reducing bacteria capable of anaerobically oxidizing short-chain non-methane hydrocarbons is described. The short-chain hydrocarbons ethane, propane and butane are constituents of natural gas. They are usually assumed to be of thermochemical origin 1 , but biological formation of ethane and propane has been also observed 2 . Microbial utilization of short-chain hydrocarbons has been shown in some aerobic species 3 , 4 but not in anaerobic species of bacteria. On the other hand, anaerobic utilization of short-chain hydrocarbons would in principle be expected because various anaerobic bacteria grow with higher homologues (≥C 6 ) 5 . Indeed, chemical analyses of hydrocarbon-rich habitats with limited or no access of oxygen indicated in situ biodegradation of short-chain hydrocarbons 6 , 7 , 8 , 9 , 10 . Here we report the enrichment of sulphate-reducing bacteria (SRB) with such capacity from marine hydrocarbon seep areas. Propane or n -butane as the sole growth substrate led to sediment-free sulphate-reducing enrichment cultures growing at 12, 28 or 60 °C. With ethane, a slower enrichment with residual sediment was obtained at 12 °C. Isolation experiments resulted in a mesophilic pure culture (strain BuS5) that used only propane and n -butane (methane, isobutane, alcohols or carboxylic acids did not support growth). Complete hydrocarbon oxidation to CO 2 and the preferential oxidation of 12 C-enriched alkanes were observed with strain BuS5 and other cultures. Metabolites of propane included iso- and n -propylsuccinate, indicating a subterminal as well as an unprecedented terminal alkane activation with involvement of fumarate. According to 16S ribosomal RNA analyses, strain BuS5 affiliates with Desulfosarcina / Desulfococcus , a cluster of widespread marine SRB. An enrichment culture with propane growing at 60 °C was dominated by Desulfotomaculum -like SRB. Our results suggest that diverse SRB are able to thrive in seep areas and gas reservoirs on propane and butane, thus altering the gas composition and contributing to sulphide production.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Anaerobic bacteria / Anaerobiosis / Bacteria / Bacteria, Anaerobic - classification / Bacteria, Anaerobic - genetics / Bacteria, Anaerobic - metabolism / Bacteriological methods and techniques used in bacteriology / Bacteriology / Biodegradation / Biological and medical sciences / Butanes - metabolism / Carbon dioxide / Carboxylic acids / Desulfococcus / Desulfosarcina / Enrichment / Ethane / Ethane - metabolism / Fundamental and applied biological sciences. Psychology / Habitats / Humanities and Social Sciences / Hydrocarbons / Hydrocarbons - chemistry / Hydrocarbons - metabolism / Kinetics / letter / Marine / Metabolites / Methane / Microbiology / Molecular Sequence Data / multidisciplinary / Natural gas / Oceans / Oceans and Seas / Oxidation / Oxidation-Reduction / Oxidation-reduction reaction / Phylogeny / Physiological aspects / Propane / Propane - metabolism / Reservoirs / RNA, Ribosomal, 16S / Science / Science (multidisciplinary) / Sediments / Sulfate reduction / Sulfates / Sulfates - metabolism / Sulfides / Sulfur-Reducing Bacteria - classification / Sulfur-Reducing Bacteria - genetics / Sulfur-Reducing Bacteria - metabolism