Abstract
This article describes the use of quantitative PCR for measuring bacterial abundance in environmental samples. The two approaches discussed are: (1) The use of an internal PCR standard constructed to be the same size and have the same sequence as the primary amplification target, but differing from the primary target by 2–3 bases, corresponding to a unique restriction site. This allows the amount of target amplicon to be compared with the internal standard and circumvents the problem of differential amplification efficiencies when using dissimilar targets and standard amplicons. (2) The use of Taqman technology (Applied Biosystems, Foster City, California) with a dual labeled oligonucleotide probe which binds internal to the PCR primers. The detection of Bacteroides is used as an example for both approaches.