E. coli metabolomics: Capturing the complexity of a "simple" model

As the workhorse of early studies on metabolism, the metabolic pathways of E. coli are arguably the best characterized. The richness of information available about its pathways is broader than for any other model. However, in spite of decades of descriptive work, only recently can a significant number of E. coli metabolic network constituents be analyzed simultaneously. The advent of metabolomic methods that allow to capture qualitative as well as quantitative information about the intracellular and extracellular metabolite profiles is starting to shed light on the remaining complexity of this simpler model. Here we describe important findings about the physiology of E. coli resulting from emerging metabolomic studies. While a vast number of intracellular metabolites in E. coli still remain to be characterized, the information obtained from those studies can provide an unprecedented amount of information about metabolic pathways including their functional elucidation, enzyme activity, metabolic fluxes, network robustness, or even the discovery of completely novel reactions or pathways. These results are also being used to populate rich databases and to develop computational models of E. coli metabolism that have already proven effective to predict cellular states and will shed light on complex and until now still elusive regulatory principles.