Construction of isogenic mutants in Streptococcus gallolyticus based on the development of new mobilizable vectors

Streptococcus gallolyticus is an emerging cause of infective endocarditis that has been epidemiologically linked to colorectal cancer. S. gallolyticus is poorly transformable using electroporation and no defined mutant has been published yet. Hence, we used mobilization to introduce plasmid DNA from Streptococcus agalactiae into S. gallolyticus using the transfer origin of the conjugative element TnGBS1 (oriTTnGBS1), followed by a classical homologous recombination technique. Two isogenic mutants of S. gallolyticus UCN34, one deleted for the pil1 pilus operon and another for the sortase A gene, were constructed and characterized. This genetic tool should help in unravelling virulence mechanisms of this bacterium.