FIG. 3.

Quantification of the number of O. formigenes genomes in a sample by using the QC-PCR. Dilutions, ranging from 50 to 250,000 molecules of purified plasmid containing the competitive template, were used either as DNA templates in PCR to establish standard curves (top, center panel) or as competitive DNA by mixing with 2 × 10⁴ (left panel) or 2 × 10² (right panel) copies of purified O. formigenes OxB genomes. PCR band intensities were scanned and normalized for molecular mass, and the log ratios of O. formigenes to template band intensities were graphed to determine log equivalence (bottom panels). QCT, quantitative competitive template.