Genomic architecture of genes involved with nitrate/nitrite metabolism in E. coli , D. dadantii and P. atrosepticum. Direction (forward or reverse complement indicated by (rc)) was selected to maximize collinearity. Colors are indicative of OrthoMCL grouping unless otherwise indicated by footnotes such that each color marks the genes associated with E. coli clusters and members of orthologous groups from D. dadantii 3937 and P. atrosepticum SCRI1043 labeled with the same name. White genes are singletons with no orthologs in the other two organisms. 1. narPQ and narXL are paralogous components in E. coli and P. atrosepticum SCRI1043. The narQ locus is located elsewhere in the chromosome, 2. ccmABCDEFGH, type 1 cytochrome C biogenesis system contains a duplication of ccmH in P. atrosepticum, 3. OrthoMCL cluster that includes the nirB encoded large subunit from E. coli, a single protein from D. dadantii 3937 annotated as nirB, and two paralogs from P. atrosepticum SCRI1043, annotated as nirB and nasB.