The type IVb pilus of plasmid TP114 displays adhesins conferring conjugation specificity and is required for DNA transfer in the mouse gut microbiota.

Type IV pili (T4P) are one of the most common surface appendages in bacteria. These pili are involved in different biological processes such as adherence, motility, competence, conjugation, and pathogenesis. Conjugative plasmids sometimes encode T4P. Here, we describe the type IVb T4P of TP114, a conjugative plasmid recently shown to disseminate at high rates in the mouse intestinal tract. This pilus is composed of the major (pilS) and minor (pilV) pilins which are both required for conjugation in broth and the gut microbiota, but not on a solid support. The 3-end of pilV coding sequence is part of a shufflon, composed of various PilV C-terminal cassettes that can be rearranged by a tyrosine recombinase. The shufflon acts as a biological switch, introducing amino acid variabilities within the PilV protein, allowing donor bacterium to bind different recipient cells during conjugation in broth or in vivo. We have identified eight pilV variants in TP114, including one that has not been described in other shufflons. All variants were found to allow conjugative transfer with different specificities of recipient bacteria. We conclude that T4P encoded by TP114 plays a major role in mating pair stabilization in unstable environments such as the mouse gut microbiota and that the various PilV variants provided by shufflon contribute to the broadening of the conjugative host range.