FIG. 2.

The effect of capsule on transformation of the pneumococcus. After treatment to induce competence with CSP, the transformation frequencies [number of transformants/(number transformants + nontransformants)] with chromosomal DNA (A) or plasmid DNA (B) was compared in D39, an encapsulated parent strain (checkered bars); P125 and P126, opaque and transparent variants of an unencapsulated mutant of D39, respectively (gray and solid bars, respectively); and P138, a transformant of the unencapsulated mutant expressing a type 3 capsular polysaccharide (hatched bars). Values are the means of duplicate determinations of at least two independent experiments (n) ± standard deviations (error bars) (when n ≥ 3). There was no significant difference between opaque and transparent variants in the absence of capsule. Asterisks represent significant differences (P < 0.001; Student’s t test) in transformation frequency between unencapsulated and encapsulated strain variants.