FIG 1.
Optimization of DNA thermo-protection buffer composition and duration of heat inactivation at 99°C. (A) Extracted DNA was heated in 25 mM HEPES buffer, pH 7.5, containing 0, 0.5, 1, or 2 M KCl. Input DNA comprised 118 ng of (i) BCG DNA, (ii) BCG and sputum DNA, (iii) sputum DNA. Each DNA type was heated at 99°C, for 30 min. (B) Impact of heating duration on DNA yield. DNA remaining post heating is expressed as a percentage of the input DNA for (i) 105 BCG cells, (ii) 1 ml sputum spiked with 105 BCG cells, or (iii) 1 ml sputum. BCG DNA degraded more slowly than sputum DNA, indicating the potential for enrichment relative to human DNA at earlier time points.