Growth strategy of microbes on mixed carbon sources

TL;DR

This paper presents a network-based model explaining why microbes choose between sequential and simultaneous consumption of carbon sources, supported by experimental validation, advancing understanding of microbial nutrient strategies.

Contribution

It introduces a topological network model that predicts microbial growth strategies and quantifies carbon source utilization, providing a new framework for understanding microbial metabolism.

Findings

Model accurately predicts diauxic and co-utilization behaviors.

Experimental data confirms predicted carbon source proportions.

Provides a quantitative framework for microbial nutrient choice.

Abstract

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.