Orthologues of M. tuberculosis PPE genes present in the genomes of M. smegmatis, M. sp . KMS, M. avium paratuberculosis, M. leprae, M. ulcerans and M. marinum. PPE genes identified in the genomes of M. smegmatis (highlighted in blue), M. sp. KMS (highlighted in grey), M. avium paratuberculosis (highlighted in purple), M. leprae (highlighted in yellow), M. ulcerans (highlighted in teal), and M. marinum (highlighted in green) are superimposed on the phylogenetic tree generated for the PPE gene family in M. tuberculosis H37Rv (see Figure 6). M. avium paratuberculosis-, M. leprae-, M. ulcerans- and M. marinum-specific genes are omitted. M. flavescens, M. vanbaalenii, M. sp. MCS and M. sp. JLS PPE genes show a similar distribution to M. smegmatis and are thus not indicated on the figure.