How Many Microorganisms Are Present? Quantitative Reverse Transcription PCR (qRT-PCR)

Abstract

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