FIG. 3.
High-frequency transformation permits visible selection of transformants with lacZ expression. B. dermatitidis yeast was cocultivated with LBA1100::pBTS92 at a high ratio of bacteria to yeast. After 5 to7 days of unselected growth, the yeast cells were stained in situ with X-Gal and processed for photography. (A) A total of 2 × 104 ER-3 yeast cells were cocultivated with ∼6 × 107 bacteria. Individual blue-staining foci of lacZ+ cells are seen on a tan background of untransformed B. dermatitidis. Note 1-cm scale bar. (B) A total of 103 strain 26199 yeast cells were cocultivated with 3 × 107 bacteria. A close-up image of a single blue-sectored colony is shown. Note 1-mm scale bar.