Genomics and Metabolism in Escherichia coli
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Genomics and Metabolism in Escherichia coli MARGRETHE HAUGGE SERRES AND MONICA RILEY
Escherichia coli as a Model Organism When did Escherichia coli attain the status of a model organism? Over many decades biochemical researchers used E. coli as a source of enzymes supplementing the more common sources such as rat liver, pigeon breast and spinach, but that practice in itself did not confer the status of model organism. A giant step was taken in 1955 when the Carnegie Institute of Washington Biophysics group headed by R.B. Roberts published a large monograph reporting its own work and the work of others on the intermediary metabolism of E. coli (Roberts et al., 1955). Model organism status was gained when genetic transfer capabilities were discovered (Wollman et al., 1959; Lederberg and Tatum, 1946). In this same era, Maaloe and colleagues untangled the dynamics of E. coli cell physiology by documenting the effects of shifts in growth conditions on macromolecule synthesis (summarized in Maaloe and Kjeldgaard, 1966). Elucidation of the operon theory of regulation of gene expression (by means of a combination of bacterial genetics and enzyme assays; Pardee et al., 1959; Jacob and Monod, 1961) firmly established E. coli as a lead microorganism for molecular biology research. Over 50 years of intense investigation of laboratory strains of E. coli have produced a vast amount of experimental information. The unique repository of summarized information on E. coli genetics, cell biology, physiology, metabolism, evolution and population biology is the twovolume, 155-chapter, and nearly 3000-page multi-author work coordinated by senior editor F. C. Neidhardt and published by ASM Press (Neidhart, 1996). The object of most of this study has been the nonpathogenic strain K-12. Medical microbiology throughout this time and to the present dealt with entero- and uropathogenic E. coli strains, but this essay is about the nonvirulent strain K-12. Escherichia coli plays a prominent role in the new field of genomics, the study of entire
genomes, their chemistry, and the molecular biology of all gene products. Inasmuch as gene cloning allows introduction of genes from any source into E. coli (Sambrook et al., 1989), this organism has become a tool for studying its own molecular biology as well as that of other taxa. One of perhaps 25 microorganisms for which an entire nucleotide sequence is known (Blattner et al., 1997), E. coli plays a prominent role in reaping biological information from the complete nucleotide sequences of genomes.
The Genomics of Escherichia coli The complete sequence of the 4.7 Mb chromosome of E. coli strain MG1655 was announced in 1997 (Blattner et al., 1997). A substantial portion of another K-12 strain W3110 was completed independently (Itoh et al., 1999). What is the point of having a complete genome sequence of an organism? When we understand how every gene product (protein or RNA) of a genome functions and how those proteins and nucleic aci
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