A classic problem in microbiology is that bacteria display two types of growth behavior when cultured on a mixture of two carbon sources: in certain mixtures the bacteria consume the two carbon sources sequentially (diauxie) and in other mixtures the bacteria consume both sources simultaneously (co-utilization). The search for the molecular mechanism of diauxie led to the discovery of the lac operon and gene regulation in general . However,  why microbes would bother to have different strategies of taking up nutrients remained a mystery . Here we show that diauxie versus co-utilization can be understood from the topological features of the metabolic network. A model of optimal allocation of protein resources to achieve maximum growth quantitatively explains why and how the cell makes the choice when facing multiple carbon sources . Our work solves a long-standing puzzle and sheds light on microbes' optimal growth in different nutrient conditions .
A classic problem in microbiology is that bacteria display two types of growth behavior when cultured on a mixture of two carbon sources: the two sources are sequentially consumed one after another (diauxie) or they are simultaneously consumed (co-utilization). The search for the molecular mechanism of diauxie led to the discovery of the lac operon . However, questions remain as why microbes would bother to have different strategies of taking up nutrients . Here we show that diauxie versus co-utilization can be understood from the topological features of the metabolic network. A model of optimal allocation of protein resources quantitatively explains why and how the cell makes the choice . In case of co-utilization, the model predicts the percentage of each carbon source in supplying the amino acid pools, which is quantitatively verified by experiments . Our work solves a long-standing puzzle and provides a quantitative framework for the carbon source utilization of microbes .
R
in certain mixtures the bacteria consume the two carbon sources sequentially
the two sources are sequentially consumed one after another
R
and in other mixtures the bacteria consume both sources simultaneously
or they are simultaneously consumed
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and gene regulation in general
A
questions remain as
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remained a mystery
D
to achieve maximum growth
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when facing multiple carbon sources
. In case of co-utilization, the model predicts the percentage of each carbon source in supplying the amino acid pools, which is quantitatively verified by experiments
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sheds light on microbes' optimal growth in different nutrient conditions
provides a quantitative framework for the carbon source utilization of microbes