Black and white with some shades of grey: The diverse responses of inducible metabolic pathways in Escherichia coli

Christopher V. Rao, Santosh Koirala

Research output: Contribution to journalComment/debate


The metabolic pathways for many sugars are inducible. This process has been extensively studied in the case of Escherichia coli lactose metabolism. It has long been known that gratuitous induction of the lac operon with non-metabolizable lactose analogues generates an all-or-nothing response, where some cells express the lac genes at a maximal rate and others not at all. However, the response to lactose itself is graded, where all cells express the lac genes in proportion to lactose concentrations. The mechanisms generating these distinct behaviours in lactose metabolism have been a topic of many studies. Despite this large body of work, little is known about how other pathways respond to their cognate sugars. An article of MolecularMicrobiology investigated the response of eight metabolic pathways in E. coli to their cognate sugars at single-cell resolution. The authors demonstrate that these pathways exhibit diverse responses, ranging from graded to all-or-nothing responses and combinations thereof. Remarkably, they were able to interpret these responses using a simple mathematical model and identify the mechanisms likely giving rise to each.

Original languageEnglish (US)
Pages (from-to)1079-1083
Number of pages5
JournalMolecular Microbiology
Issue number6
StatePublished - Sep 1 2014


ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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