Microbial redox processes in deep subsurface environments and the potential application of (per)chlorate in oil reservoirs

• Published in: Frontiers in microbiology Vol. 5; p. 428
• Main Authors: Liebensteiner, Martin G, Tsesmetzis, Nicolas, Stams, Alfons J M, Lomans, Bartholomeus P
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 01.09.2014
• Subjects: (per)chlorate reduction; anaerobic redox processes; bacillus-thermoleovorans; deep subsurface; extracellular electron-transfer; gen. nov; geobacillus-thermodenitrificans; MEOR; Microbiology; nitrate; nitrate-reductase; oil reservoirs; perchlorate reduction; petroleum reservoirs; sp-nov; sulfate-reducing bacteria; trimethylamine-n-oxide; (per)chlorate reduction; anaerobic redox processes; deep subsurface; reservoir souring; nitrate; oil reservoirs; MEOR
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2014.00428

The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (per)chlorate for bioremediation, souring control, and microbial enhanced oil recovery are addressed.