| Cellular metabolism consists of a complex network of chemical reactions, which transform hundreds of small molecules into each other in order to secure a reliable supply of energy and building blocks. Understanding how cells manage their resources and network flows under different environmental conditions is a key question in systems biology. In addition to being relevant for practical applications, such as the identification of key genes involved in metabolic diseases, or the design of bioprocesses for optimal production of biofuels, this question is tightly related to the broader problem of how biological networks evolve through natural selection. By implementing steady state models of genome-scale metabolic networks and studying the response to single and double gene deletions in microbial cells, we formulate new hypotheses about the capacity of cells to reach optimal states, and uncover a global organization of genes and pathways into hierarchical modules associated with different biological functions. |
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