Effect of Slow Growth on Metabolism of <i>Escherichia coli</i> , as Revealed by Global Metabolite Pool (“Metabolome”) Analysis

TLDR

Escherichia coli growing on glucose in minimal medium regulates its metabolite pools in response to environmental conditions. The authors tracked pool changes by 14C‑glucose labeling and two‑dimensional thin‑layer chromatography, confirmed amino‑acid pools with independent analysis, and examined an rpoS mutant to assess regulatory effects. Metabolite pool sizes and phosphorimaging spot intensities varied reproducibly with growth rate, showing marked changes in key metabolites such as glutamate, aspartate, trehalose, adenosine, UDP‑sugars, and putrescine, while an rpoS mutant altered only a subset of these changes, indicating that global metabolome analysis uncovers novel aspects of metabolic regulation.

Abstract

ABSTRACT Escherichia coli growing on glucose in minimal medium controls its metabolite pools in response to environmental conditions. The extent of pool changes was followed through two-dimensional thin-layer chromatography of all 14 C-glucose labelled compounds extracted from bacteria. The patterns of metabolites and spot intensities detected by phosphorimaging were found to reproducibly differ depending on culture conditions. Clear trends were apparent in the pool sizes of several of the 70 most abundant metabolites extracted from bacteria growing in glucose-limited chemostats at different growth rates. The pools of glutamate, aspartate, trehalose, and adenosine as well as UDP-sugars and putrescine changed markedly. The data on pools observed by two-dimensional thin-layer chromatography were confirmed for amino acids by independent analysis. Other unidentified metabolites also displayed different spot intensities under various conditions, with four trend patterns depending on growth rate. As RpoS controls a number of metabolic genes in response to nutrient limitation, an rpoS mutant was also analyzed for metabolite pools. The mutant had altered metabolite profiles, but only some of the changes at slow growth rates were ascribable to the known control of metabolic genes by RpoS. These results indicate that total metabolite pool (“metabolome”) analysis offers a means of revealing novel aspects of cellular metabolism and global regulation.