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B. O. Palsson develops quantitative descriptions of metabolism. With J. S. Edwards, he reconstructed the metabolic capabilities of Escherichia coli MG1655 by combining its annotated genome, biochemical literature and strain-specific information. The resulting network connected hundreds of genes to the chemical reactions their products support.^[ref]

The contribution made a distinction experimentally useful: a list of genes is not yet a prediction of how a cell can grow. A metabolic network adds reaction stoichiometry and environmental constraints, allowing predicted growth or nutrient requirements to be compared with measurements. Such predictions remain conditional on the reactions and constraints included.

J. S. Edwards coauthored the 2000 reconstruction of the Escherichia coli MG1655 metabolic network with B. O. Palsson. The work combined annotated sequence information with biochemical and strain-specific evidence to connect genes, enzymes and chemical reactions.^[ref]

For example, deleting a reaction-associated gene from a model can remove a route to an essential metabolite, predicting a growth requirement that can be tested experimentally. Alternative routes may preserve growth. The contribution helped make genome annotation into a system whose predictions could be checked, while exposing assumptions and gaps in the underlying metabolic knowledge.