The heterogeneity of reaction fluxes present in metabolic networks can be exploited to construct  high-flux fluctuation backbones as reduced versions of metabolism. These backbones maintain all relevant information while displaying a substantially decreased number of interconnections and, hence, they become a useful tool to extract main metabolic highways and so to unveil important biological information. Here, we disclose the metabolic backbone of Escherichia coli using  computationally predicted fluxes that maximize the growth rate in glucose  medium, and we contrast it with the backbone of Mycoplasma pneumoniae, a much URLanism. We find that the core of both backbones are mainly composed of reactions in ancient pathways, meaning that those reactions still remain at present significant for biomass production. At the same time, a comparative analysis of  E. coli backbones in different media leads to the identification of pathways sensitive to environmental changes. Backbones, as networks of metabolites connected by the most relevant fluxes, are thus useful to trace simultaneously both  evolution and adaptation fingerprints in cell metabolism .
The heterogeneity of reaction fluxes present in a metabolic network can be exploited to construct the high-flux fluctuation backbone as a reduced version of metabolism. The backbone maintains all relevant information while displaying a substantially decreased number of interconnections and, hence, it becomes a useful tool to extract relevant metabolic routes which unveil important biological information. Here, we disclose the metabolic backbone of Escherichia coli using the computationally predicted fluxes which maximize the growth rate in glucose minimal medium, and we contrast it with the backbone of Mycoplasma pneumoniae, a much URLanism. We find that the core of both backbones are mainly composed of reactions in ancient pathways, meaning that those reactions still retain at present the central role in the evolved metabolism. In E. coli, the analysis of the core reveals a dominant direction with the synthesis of purines and pyrimidines and the metabolism of lipids ensuing after energy metabolism. At the same time, a comparative analysis of the backbone of E. coli in different media leads to the identification of pathways sensitive to environmental changes. The metabolic backbone of URLanism, as a network of metabolites connected by the most relevant fluxes, is thus useful to trace simultaneously both its evolution and adaptation fingerprints .
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metabolic networks
a metabolic network
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the
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backbones as reduced versions
backbone as a reduced version
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These backbones maintain
The backbone maintains
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they become
it becomes
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main metabolic highways and so to
relevant metabolic routes which
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the
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that
which
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minimal
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remain at present significant for biomass production.
retain at present the central role in the evolved metabolism. In E. coli, the analysis of the core reveals a dominant direction with the synthesis of purines and pyrimidines and the metabolism of lipids ensuing after energy metabolism.
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the backbone of
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backbones
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Backbones, as networks
The metabolic backbone of URLanism, as a network
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are
is
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its
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in cell metabolism