Applied Microbiology and Molecular Biology in Oilfield Systems

Abstract

Quantitative reverse transcription PCR (qRT-PCR) is a variation of conventional quantitative or real-time PCR, whereby mRNA is first converted into the comple- mentary DNA (cDNA) by reverse transcription, the cDNA is then subsequently quantified by qPCR. The use of mRNA as the initial template allows the quantifi- cation of gene transcripts, rather than gene copy numbers. mRNA is only produced by actively metabolising cells and is produced by its corresponding gene to pro- vide a ‘blueprint’ in order for a cell to manufacture a specific protein. Conventional qPCR detects not only DNA present in actively metabolising cells but also inactive and dead cells. qRT-PCR has the advantage that only actively metabolising cells are detected, hence provides a more reliable measure of microbial activity in oil- field samples. When qRT-PCR is combined with primers and probes for specific genes, the activity of microbial processes important in the oilfield, such as sulphate reduction, methanogenesis and nitrate reduction can be monitored.