Current view of the global population structure of the Brucella genus. Clustering was done using the Neighbor Joining (NJ) algorithm. The microti/neotomae cluster was used to root the tree. The dendrogram is based upon more than 500 genotypes, observed by typing more than 750 strains [see Additional file 1]. The terrestrial mammal strains data were compiled from [5, 17, 19–23, 37]. The colour code reflects the Brucella species (or some highly specific biovars). The publications from which the data were derived are indicated. The long blue branch close to the B. pinnipedialis cluster represents the human isolate from New Zealand (MLST ST27).