--under construction--

Block duplications of known operons

1. xylFGH (xylose transport)
2. glnHPQ (glutamine transport)
3. acrAB (acriflavine resistance)
4. potFGHI (putrescine transport)
5. narGHJI (nitrate reductase)
6. fdnGHI (formate dehydrogenase)
7. hycABCDEFGH (hydrogenase)
8. oppABCDF (peptide transport)
9. fixABC (role in redox process)
10. dmsABC (dimethyl sulfoxide reductase)

Other block duplications

1. yahFGI
2. sfmACD
3. yeeSTUV
4. yccCYZ
5. sgaHUE
6. ybcVX
7. yqiIHG
8. yjbHGF
9. yfd

Legend to these figures

Examples of operon duplication and evolution from the E. coli K12 genome. Block duplicated segments with conserved gene content and order are shown. Each gene family (or COG) is represented by a different color, experimentally identified operons (Itoh et al., 1999) are marked with a red box, and predicted horizontally acquired genes (Lawrence and Ochman, 1998) are marked with a bleu box. Clear cases of operon content evolution by deletion, gene fission and tandem duplication are observed in these examples.

References:

Itoh, T. et al. (1999) Evolutionary instability of operon structures disclosed by sequence comparisons of complete microbial genomes. Mol Biol Evol 16, 332-346

Lawrence, J.G. and Ochman, H. (1998) Molecular archaeology of the Escherichia coli genome. PNAS 95, 9413-9417