┌─ Escherichia coli (28-376/376) B354   
┬─────────────────────────────────────────────────────────────────┴── Escherichia coli (19-367/367) MS 145-7   
└─────────────────────────────────────────────────────────────────┬─ Escherichia coli 1827-70 (4)  
                                                                  └┬─ Escherichia coli M718   
                                                                   └┬─ Escherichia coli K12 (119)  
                                                                    └┬─ Escherichia coli 101-1 (5)  
                                                                     └─ Escherichia coli 2362-75   
  
Thymidylate synthase (EC 2.1.1.45) (7)