Table 1.

List of genomes, with accession numbers and taxonomic assignment, used in this study.

Species (Strain)	Accession No.	Proteobacteria division
Rickettsia prowazekii	NC_000963	α
Neisseria meningitidis MC58	NC_003112	β
Neisseria meningitidis Z2491	NC_003116	β
Ralstonia solanacearum	NC_003295	β
Blochmannia floridanus	NC_005061	γ
Buchnera aphidicola (Baizongia pistaciae)	NC_004545	γ
Buchnera aphidicola (Schizaphis graminum)	NC_004061	γ
Buchnera aphidicola (Acyrthosiphon pisum)	NC_002528	γ
Escherichia coli K12	NC_000913	γ
Escherichia coli O157:H7 EDL933	NC_002655	γ
Haemophilus influenzae Rd	NC_000907	γ
Pasteurella multocida	NC_002663	γ
Pseudomonas aeruginosa	NC_002516	γ
Salmonella enterica subsp. enterica serovar Typhi	NC_003198	γ
Salmonella typhimurium LT2	NC_003197	γ
Vibrio cholerae	NC_002505	γ
Wigglesworthia glossinidia brevipalpis	NC_004344	γ
Xanthomonas axonopodis pv. citri str. 306	NC_003919	γ
Xanthomonas campestris pv. campestris str. ATCC 33913	NC_003902	γ
Xylella fastidiosa	NC_002488	γ
Yersinia pestis KIM	NC_004088	γ