The method is based on electroporation

of bifidobacterial cells, which were made competent by an optimized methodology Selleck beta-catenin inhibitor 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. Bifidobacteria are Gram-positive G+C%-rich, anaerobic/microaerophilic, fermentative bacteria, which are often Y- or V-shaped (Ventura et al., 2007). Bifidobacterium represents one of the most numerically abundant bacterial genera of the human gut microbiota in infants and is presumed to play a fundamental role in host health, which

drives their wide-spread use as probiotic bacteria in many functional foods. This commercial exploitation of probiotic bifidobacterial strains has fuelled scientific interest in these bacteria to identify the genomic traits that are responsible for the claimed beneficial activities. To exploit the full potential of these microorganisms for applications as probiotic ingredients, further knowledge is required on their molecular biology and genetics. However, molecular studies of Bifidobacterium are severely hampered by the absence of effective genetic tools, including efficient transformation protocols. So far, several Bifidobacterium strains, including members of Bifidobacterium RAD001 clinical trial bifidum and Bifidobacterium asteroides, have been shown to be nontransformable or very poorly transformable (Argnani et al., 1996). Many factors may contribute to bifidobacterial recalcitrance

for acquiring exogenous DNA, such as the presence of a thick (multilayered) Amobarbital and complex cell wall (Fischer et al., 1987), intracellular restriction/modification barriers (Hartke et al., 1996; Schell et al., 2002; O’Connell Motherway et al., 2009), and sensitivity to environmental stresses, in particular oxygen, to which these strictly anaerobic bacteria are exposed to during the preparation of competent cells and transformation procedure. With the advent of the genomics era, many bifidobacterial genomes have been fully decoded (for reviews, see Turroni et al., 2011; Ventura et al., 2009), which has thus provided a huge amount of genetic data that can be exploited to study genome functionality. Such studies are needed to understand the molecular mechanisms sustaining the interaction of bifidobacteria with its host as well as with other members of the gut microbiota (Hartke et al., 1996; Schell et al., 2002; Sela et al., 2008; Ventura et al., 2009; Turroni et al., 2011). However, to perform such functional genomic investigations, it will be necessary to develop transformation protocols as well as to implement gene knock-out methodologies effective for bifidobacteria. In this report, we describe the development of a protocol for efficient and reproducible genetic transformation of B.