ABSTRACT
Recent investigations have demonstrated that hydrocarbon biodegradation occurs under methanogenic conditions, a microbial process that is often prevalent in deep subsurface reservoirs and shallow anoxic sediments devoid of electron acceptors. However, the metabolic pathways utilized by methanogenic hydrocarbon-degrading consortia and the key microbial community members involved are not well known. Here, we present a case study that used a multi-pronged approach to help identify the key players and metabolic reactions that can occur during methanogenic crude oil biodegradation. Incubations established with produced water from a heavy oilfield were interrogated with analytical chemistry and molecular biology approaches over a 17-month time period, revealing that fumarate addition does occur as a mechanism of hydrocarbon activation under methanogenic conditions. Detected bssA and assA gene sequences affiliated most closely with Desulfotomaculum and Smithella (also abundant in 16S rRNA gene surveys), suggesting that these phylotypes are important hydrocarbon activators in crude oil-containing methanogenic ecosystems.
