Unraveling the molecular mechanisms of DNA capture by the Com pilus in naturally transformable monoderm bacteria

Bacteria are capable of evolving and diversifying very rapidly by acquiring new genetic material via horizontal gene transfer (HGT). Transformation is a widespread mechanism of HGT, which results from the capture of extracellular DNA by surface-exposed pili belonging to the type 4 filament (T4F) superfamily. How T4F-composed of major and minor pilins-interact with DNA remains poorly understood, especially in monoderm species that use a unique T4F for DNA capture, known as Com pilus or T4dP. The significance of this work is in characterizing a novel mode of DNA-binding by showing that the interface between two minor pilins, part of a tip-located complex of four pilins-found in different T4F-has been functionalized in monoderms to capture DNA. This is an evolutionary mechanism promoting the exceptional functional versatility of T4F.