microbiology, Vol 144, 3061-3068, Copyright © 1998 by Society for General Microbiology
Electrotransformation and natural transformation of Streptococcus pneumoniae: requirement of DNA processing for recombination
J Lefrancois, MM Samrakandi and AM Sicard
Laboratoire de Microbiologie et de Genetique Moleculaire du CNRS and Universite Paul Sabatier, Toulouse, France. jacques@ibcg.biotoul.fr
Electrotransformation has been used as a tool to introduce genes carried on
replicative vectors in hundreds of bacterial species. In this study, the
technique was used to try to obtain recombination of markers in the
chromosome of the naturally transformable bacterium Streptococcus
pneumoniae. Recombination was not observed even using naturally competent
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 bacterium. The
integration of markers into the chromosome in naturally competent cells
must require DNA processing during entry. Electrotransformation 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 homologous
pairing.
