The phylogenetic tree of representative PDOs whose genes are physically linked to sqr in bacterial genomes. 69 representative PDOs were used for phylogenetic tree construction with reference sequences. PDOs belong to the metallo-beta-lactamase superfamily, and several related proteins, such as glyoxalase II (GloB) proteins, were also included as references. The representative proteins were labeled with their GenBank accession numbers and bacterial genera. These sequences were aligned by using ClustalW, and the tree was built by using MEGA6. Reference proteins with accession number were given below. Type I PDOs: SaPdoI (YP_003957083.1), CpPdoI (YP_297536.1), MxPdoI (YP_633997.1), HsPdoI (NP_055112.2), CaPdoI (YP_007162862.1), BvPdoI (ZP_00420127.1), AtPdoI (NP_974018.3), AcPdoI (AEK59246.1). Type II PDOs: XfPdoII (NP_298058.1), SmPdoII (NP_435818.1), CpPdoII (YP_297791.1), PaPdoII (NP_251605.1), BxPdoII (YP_554628.1), AfaPdoII (AAK89929.1), AfePdoII (ZP_11421028.1), AfrPdoII (YP_002424776.1). Type III PDOs: ZpPdoIII (ADF52140.1), SaPdoIII (WP_000465474.1), BcPdoIII (EEK49737.1). Glyoxalase II and related proteins: aGLX2-5 (NP_850166.1), AtGloB1 (NP_356997.2), BcII (AAA22276.1), CphA (CAA40386.1), EcGloB1 (NP_414748.1), EcGloB2 (NP_415447.1), hGLX2 (CAA62483.1), HiGloB1 (ADO96205.1), PaGloB2 (NP_249523.1), PpGloB2 (ABQ76961.1), YcbL (CAD05397.1) and ytGLO2 (CAA71335.1).