The gene orientation of all putative luxRI operons in available Roseobacter genomes. Green arrows represent AHL synthase encoding genes (luxI), orange arrows represent AHL binding response regulators (luxR), and black arrows represent adjacent genes. Abbreviations used: Crotonyl CoA, Crotonyl CoA reductase; HK, histidine kinase; HK/RR, hybrid histidine kinase/response regulator; HK/REC, histidine kinase with REC domain; CHP, conserved hypothetical protein; RND, RND multidrug efflux pump; Sig B, sigma B factor; SCD, short chain dehydrogenase; Trans., transposase; L17, L17 component of the 50S ribosomal protein; 2CRS, two-component regulatory system; TctA, TctA family transmembrane transporter; mdlB, mandelate dehydrogenase mdlB; spαβ, α and β subunits of sulfopyruvate decarboxylase. Rx and Ix designations above the response regulators and AHL synthases indicate their corresponding phylogentic subgroupings in Figures 1A,B, respectively. Those without Rx and Ix designations indicate unique sequences not found in the conserved groupings. The corresponding genomes that contain these topologies can be found in Table A1.