IN VITRO TRANSFORMATION OF PNEUMOCOCCAL TYPES : I. A TECHNIQUE FOR INDUCING TRANSFORMATION OF PNEUMOCOCCAL TYPES IN VITRO.

1. Type-specific S pneumococci may be transformed from one specific S type into other specific S types entirely by in vitro methods. 2. R forms of pneumococci, derived from S forms of one specific type, may be transformed into S forms of other specific types by the following in vitro procedure:-the growth of small inocula of R forms in media containing vaccines prepared from heterologous S cultures. 3. Transformation of type may be effected in this procedure by the use of small quantities of S vaccine,-quantities representing the bacteria from as little as 0.1 cc. of the original culture. 4. Transformation of type, as induced by this procedure, is most readily effected by employing anti-R serum in the culture medium. Transformation of type may be effected, however, in media which do not contain anti-R antibodies. 5. Previous findings on the thermal characteristics of the property of S vaccines responsible for transformation of type have been confirmed and extended.