An efficient and reproducible method for transformation of genetically recalcitrant bifidobacteria.

This study describes an efficient transformation system for the introduction of plasmid DNA into Bifidobacterium bifidum PRL2010 and Bifidobacterium asteroides PRL2011, for which to the best of our knowledge no transformation data have been reported previously. The method is based on electroporation of bifidobacterial cells, which were made competent by an optimized methodology based on varying media and growth conditions. Furthermore, the transformation protocol was applied in order to design a PRL2010-derivative, which carries antibiotic resistance against chloramphenicol and which was used to monitor PRL2010 colonization in a murine model.