Abstract
Abstract. Analyses of microbial communities from six water-flooding petroleum reservoirs at temperatures from 21 to 63 °C by 16S rRNA gene clone libraries indicates the presence of physiologically diverse and temperature-dependent microorganisms in these subterrestrial ecosystems. In samples originating from high-temperature petroleum reservoirs, most of the archaeal sequences belong to thermophiles affiliated with members of the genera Thermococcus, Methanothermobacter and the order Thermoplasmatales, whereas bacterial sequences predominantly belong to the phyla Firmicutes, Thermotogae and Thermodesulfobacteria. In contrast to high-temperature petroleum reservoirs, microorganisms belonging to the Proteobacteria, Methanobacteriales and Methanomicrobiales were the most encountered in samples collected from low-temperature petroleum reservoirs. Canonical correspondence analysis (CCA) revealed that temperature, mineralization, ionic type as well as volatile fatty acids showed correlation with the microbial community structures, in particular members of the Firmicutes and the genus Methanothermobacter showed positive correlation with temperature and the concentration of acetate. Overall, these data indicate the large occurrence of hydrogenotrophic methanogens in petroleum reservoirs and imply that acetate metabolism via syntrophic oxidation may represent the main methanogenic pathway in high-temperature petroleum reservoirs.
Highlights
Petroleum reservoirs represent extreme anaerobic environments because of the temperature, pressure and salinity with multiphase fluids of oil, gas and water
In order to characterize the microbial community from the different temperature petroleum reservoir, these samples were grouped into two classes: high-temperature (45 ∼ 63 ◦C) and low-temperature (21 ∼ 37 ◦C)
Six production water samples from six water-flooding petroleum reservoirs with different temperatures were analyzed by PCR amplification with bacterial and archaeal specific primer sets
Summary
Petroleum reservoirs represent extreme anaerobic environments because of the temperature, pressure and salinity with multiphase fluids of oil, gas and water. Microorganisms in such subterranean ecosystems play an important role in energy flow and nutrients cycling. Microorganisms with diverse physiological and metabolic capabilities and phylogenetic affiliations have been recovered from oil reservoirs by culture-dependent and culture-independent approaches since the first sulfatereducing bacteria (SRB) was isolated from production water of an oil reservoir (Bastin et al, 1926). Though isolation efforts have identified numerous bacterial and archaeal species that are capable of mediating various metabolic processes occurring in oil fields, culture-independent 16S rRNA genes and functional gene-based investigations have provided new information on the microbial community composition in such deep subsurface ecosystems (Li et al, 2010, 2011; Guan et al, 2012)
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