FIG. 3.

Heat denaturation and digestion with exonuclease I of bacterial 16S rRNA genes, as visualized in a 1.0% agarose gel. Lanes 1, 16S rRNA genes amplified from bulk DNA derived from river water; lanes 2, 16S rRNA genes amplified from bulk DNA derived from hot spring fluid; lanes 3, 16S rRNA gene fragments amplified from a DNA mixture that was a blend of equal amounts of bulk DNAs extracted from hot spring fluid and river water; lanes M, DNA marker (1-kb DNA ladder; Promega, Madison, WI). The temperatures of the heat treatments are indicated at the top. The size of each amplified 16S rRNA gene fragment was approximately 1,500 bp (arrow).