Distribution of <i>phoP</i>-<i>phoQ</i>, the magnesium transporters <i>mgtA</i> and <i>mgtB</i>, and lipid A modification genes among the insect pathogen <i>Photorhabdus luminescens</i> and recently derived and ancient insect endosymbionts.

Estimated age of association (in million of years) is shown for ancient insect symbionts [58]. “P” indicates that a given sequence was determined to be a pseudogene. ”N. A.” signifies not applicable. Numbers of acidic residues within the acidic patch are displayed for PhoQ homologues. Note also that Candidatus Serratia symbiotica maintains a truncated PhoQ homologue.