Method for absolute quantification of microbial communities by using both microarrays and competitive PCR

We investigated an improved method that combines competitive PCR and microarray techniques. This approach allowed us to quantify specific bacterial groups mounted on DNA chips with accuracy close to that of real-time PCR, despite a measurement at the end point of PCR, and also to estimate the bacterial DNA content in sample DNA. Two bacterial genomic DNA mixtures for calibration curve, twelve kinds of bacterial genomic DNA (4 dilution series, duplicate) for specificity test of DNA chip probes were used. One bacterial genomic DNA mixture and extraction DNA samples from five human dental plaque samples with a sterile toothbrush (triplicate) were measured.