We assigned functions to representative members of each family through BLASTX alignment to the BLAST2GO database26. Following the common trend in bacterial species pan-genomes, most core gene families mapped to a Gene Ontology (GO) category. Most of the accessory genes, however, could not be assigned with the exception of genes responsible for horizontal gene transfer (HGT) (e.g., transposition) and signal transduction (Supplementary Table 2a,b).