Molecularanalysis ofthebacterial community ina continental high-temperatureandwater-£oodedpetroleum reservoir

Water from a continental high-temperature, long-term water-flooded petroleum reservoir in Huabei Oilfield in China was analysed for its bacterial community and diversity. The bacteria were characterized by their 16S rRNA genes. A 16S rRNA gene clone library was constructed from the community DNA, and using restriction fragment length polymorphism analysis, 337 randomly selected clones were clustered with 74 operational taxonomic units. Sequencing and phylogenetic analyses showed that the screened clones were affiliated with Gammaproteobacteria (85.7%), Thermotogales (6.8%), Epsilonproteobacteria (2.4%), low-G1C Grampositive (2.1%), high-G1C Gram-positive, Betaproteobacteria and Nitrospira (each o 1.0%). Thermopilic bacteria were found in the high-temperature water from the flooded petroleum reservoir, as well as mesophilic bacteria such as Pseudomonas-like clones. The mesophilic bacteria were probably introduced into the reservoir as it was being exploited. This work provides significant information on the structure of bacterial communities in high-temperature, long-term waterflooded petroleum reservoirs.