Methanogenes and Ammonia-Oxidation Archaeal Communities in High Temperature Oil Reservoirs pp. 39-68
Authors: (Hui Li, Bo-Zhong Mu, School of Resources and Environmental Engineering, State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai, China, and others)
Abstract: The widespread occurrence and diversity of archaea in high temperature underground oil reservoir indicates their key contribution to the material cycle and energy flow in the subsurface hot habitat. Methanogens dominated the anoxic ecosystem with amount of petroleumhydrocarbons by catalyzing the last step of carbon cycle by producing methane. The diversity of archaeal community was analyzedby 16S rRNA gene librariesconstructed fromtwo continental- and offshore, high-temperature, long-term water-flooded petroleum reservoir in China. The continentallibrary includes237 clones clustered in 28 phylotypes. The dominant members were affiliated with the order Methanomicrobiales belonged to four orders: Methanobacteriales, Methanococcales, Methanomicrobiales and Methanosarcinales. Most of the clones clustered with sequences previously described for methanogens. Theoffshore archaeal 16S rRNA gene clone libraryincluded220 randomly selected clones clustered with 28 phylotypes dominated by methanogen-like rRNA genes (Methanothermobacter, Methanobacter, Methanob-revibacter and Methanococcus)and with a lower percentage of clones belonging to Thermoprotei. The FISH results indicated that the quantity of archaea was much more than bacteria in the samples and they had close spatial distribution in situ formed compact aggregates. Some thermophilic methanogens detected had been previously isolated from a number of high-temperature petroleum reservoirs worldwide, thus they might adapt to the environments and be the common habitants of geothermally heated subsurface environments. The existence, diversity, abundance and distribution of ammonia-oxidation archaea (AOA) in the high temperature oil reservoirs were investigated by using real-time PCR and phylogenetic analysis based on amoA genes. The result demonstrated the AOA-like phylotypes were mainly clustered within two major clades of archaeal amoA sequences knownfrom water columns, sediments, and soils: clusters A and B, and few clones were related to the new genera:Candidatus ‗Nitrosocaldus yellowstonii‘. The abundance of AOA -like amoA gene ranged from2.92 ×103 to 9.21 ×104 per ml production water. Statistical analysisshowed that amoAgene fell into five groups and the distribution of amoA was of significant positive correlation with the environmental factors temperature and recovery process. Our study provided the evidence for the distribution of putative prokaryoticamoA gene in various oil reservoirs, which improved ourunderstanding of the nitrogencycling in oilfield ecosystem.