Rapid detection and quantification of bisulfite reductase genes in oil field samples using real-time PCR.

Sulfate-reducing bacteria (SRB) pose a serious problem to offshore oil industries by producing sulfide, which is highly reactive, corrosive and toxic. The dissimilatory sulfite reductase (dsr) gene encodes for enzyme dissimilatory sulfite reductase and catalyzes the conversion of sulfite to sulfide. Because this gene is required by all sulfate reducers, it is a potential candidate as a functional marker. Denaturing gradient gel electrophoresis fingerprints revealed the presence of considerable genetic diversity in the DNA extracts achieved from production water collected from various oil fields. A quantitative PCR (qPCR) assay was developed for rapid and accurate detection of dsrB in oil field samples. A standard curve was prepared based on a plasmid containing the appropriate dsrB fragment from Desulfomicrobium norvegicum. The quantification range of this assay was six orders of magnitude, from 4.5 x 10(7) to 4.5 x 10(2) copies per reaction. The assay was not influenced by the presence of foreign DNA. This assay was tested against several DNA samples isolated from formation water samples collected from geographically diverse locations of India. The results indicate that this qPCR approach can provide valuable information related to the abundance of the bisulfite reductase gene in harsh environmental samples.