Highly efficient gene transfer in the mouse gut microbiota is enabled by the Incl2 conjugative plasmid TP114

The gut microbiota is a suspected hotspot for bacterial conjugation due to its high density and diversity of microorganisms. However, the contribution of different conjugative plasmid families to horizontal gene transfer in this environment remains poorly characterized. Here, we systematically quantified the transfer rates in the mouse intestinal tract for 13 conjugative plasmids encompassing 10 major incompatibility groups. The vast majority of these plasmids were unable to perform conjugation in situ or only reached relatively low transfer rates. Surprisingly, IncI(2) conjugative plasmid TP114 was identified as a proficient DNA delivery system in this environment, with the ability to transfer to virtually 100% of the probed recipient bacteria. We also show that a type IV pilus present in I-complex conjugative plasmids plays a crucial role for the transfer of TP114 in the mouse intestinal microbiota, most likely by contributing to mating pair stabilization. These results provide new insights on the mobility of genes in the gut microbiota and highlights TP114 as a very efficient DNA delivery system of interest for microbiome editing tools. Kevin Neil et al. quantified horizontal gene transfer rates for 13 conjugative plasmids in the mouse gut microbiota to identify those that might be useful for developing microbiome editing technologies. They find that the Incl-family plasmid TP114 has a nearly 100% transfer efficiency in the mouse gut.