FIG. 1.

Comparison of the frequencies of genetic transformation in encapsulated variants. Isolates of the three types indicated below were divided into opaque (gray bars) and transparent (solid bars) phenotypes. After treatment to induce competence with CSP, the transformation frequency [number of transformants/(number transformants + nontransformants)] with chromosomal DNA (A) or plasmid DNA (B) was determined. For the type 6B isolate a spontaneous opaque revertant (hatched bars) of the transparent variant was also tested. Values are the means of duplicate determinations of at least two independent experiments (n) ± standard deviations (error bars) when n ≥ 3). Asterisks represent significant differences (P < 0.001; Student’s t test) in transformation frequency between opaque and transparent variants.