FIG 4.

Phylogenetic tree of representative bacterial species with a KdpD homologue containing a USP domain similar to the one found in the S. aureus KdpD protein. KdpD homologues were retrieved by a BLAST search, and KdpD proteins with an S. aureus-like USP domain were identified and used to build a phylogenetic tree. Species that also harbor genes coding for a protein with a diadenylate cyclase (DAC) domain (i.e., proteins with homology to the S. aureus DacA or B. subtilis DisA protein) are denoted with a dark circle, while those lacking a diadenylate cyclase are indicated with a white circle.