[Characterization of bacterial diversity in the Shengli-S12 oil reservoir by culture-dependent and culture-independent methods].

Objective: Examining bacterial diversity in an oil reservoir of Shengli oil field by both culture-independent molecular technique and enrichment method.
Methods: The heterotrophic bacteria, hydrocarbon-degrading bacteria and sulfate-reducing bacteria were enriched from S12-4 oil-well samples by the corresponding media. Then the genomic DNAs of the enrichments were extracted and the 16S rRNA gene clone libraries were constructed.
Results: The phylogenetic analysis revealed that the bacterial 16S rRNA gene clone libraries of the 3 enrichments were dominated by clones of Thermotoga, Thermaerobacter and Thermotoga, respectively. Sequences of the other co-dominant clones observed only in the enrichments of hydrocarbon-degrading bacteria and sulfate-reducing bacteria were, respectively, associated with Marinobacter and Moorella. The uncultured 16S rRNA gene library was also generated directly from total DNA of S12-4 oil-well samples by bacterial primer set. Sequence analysis of this bacterial library indicated that a large percentage of clones were highly related to the genus Pseudomonas and the dominant species emerging in the enrichment samples had a very low content in the tested oil reservoir. The significant difference of the bacterial composition between the samples obtained from independent-culture method and enrichment method implies that the specialized nutrient may lead to a distinctive selection of dominant organisms.
Conclusion: Through culture-dependent and culture-independent methods, we acquired important information on the bacterial diversity of ShengLi oil reservoir. These results may expand our understanding of the microbial diversity of oil reservoir and provide useful information for MEOR(microbial enhancement of oil recovery).