Genomic architecture of hydrogenase gene clusters from E. coli , D. dadantii and P. atrosepticum. Gene order and orientation of hydrogenase gene clusters from all three organisms are illustrated, including 4 clusters from E. coli, 2 from D. dadantii 3937 and 1 from P. atrosepticum SCRI1043. Direction (forward or reverse complement indicated by (rc)) was selected to maximize collinearity with the single hydrogenase cluster from P. atrosepticum. 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. hypC has an ortholog in D. dadantii 3937 that is located elsewhere, 2. hybF and hypA are grouped by OrthoMCL, 3. hycF (E. coli) and hyfH (D. dadantii 3937 and P. atrosepticum SCRI1043) are grouped by OrthoMCL, but E. coli hyfH is not part of the cluster (singleton), 4. fdhF has an ortholog in E. coli that is located elsewhere, 5. ascBF and ascG have orthologs in P. atrosepticum SCRI1043 that are located elsewhere, 6. OrthoMCL groups most members of the E. coli hydrogenase 3 and 4 systems.