ELECTROTRANSFORMATION AND NATURAL TRANSFORMATION OF STREPTOCOCCUS-PNEUMONIAE - REQUIREMENT OF DNA PROCESSING FOR RECOMBINATION

Electrotransformation has been used as a tool to introduce genes carri ed on replicative vectors in hundreds of bacterial species. In this st udy, the technique was used to try to obtain recombination of markers in the chromosome of the naturally transformable bacterium Streptococc us pneumoniae. Recombination was not observed even using naturally com petent cultures. Both chromosomal and cloned DNA, denatured or native, were without effect. These results suggest that it is not sufficient to introduce DNA into the cell to obtain recombinants in this bacteriu m. The integration of markers into the chromosome in naturally compete nt cells must require DNA processing during entry. Electrotransformati on of replicating plasmids is recA-independent but can be facilitated by a recA-dependent process. This facilitation required the induction of the natural competence machinery, probably involving partial homolo gous pairing.