Timing and dynamics of single cell gene expression in the arabinose utilization system

TL;DR

This study investigates the timing and variability of gene activation in individual E. coli cells responding to arabinose, revealing how uptake protein distribution influences the stochastic ON/OFF response.

Contribution

It provides a quantitative analysis of the timing dynamics of arabinose gene induction at the single-cell level, linking heterogeneity to uptake protein distribution.

Findings

Intrinsic delay times decrease with higher arabinose concentrations

Heterogeneous timing is due to variable arabinose uptake proteins

A stochastic model explains the distribution of activation delays

Abstract

The arabinose utilization system of E. coli displays a stochastic "all or nothing" response at intermediate levels of arabinose, where the population divides into a fraction catabolizing the sugar at a high rate (ON state) and a fraction not utilizing arabinose (OFF state). Here we study this decision process in individual cells, focusing on the dynamics of the transition from the OFF to the ON state. Using quantitative time-lapse microscopy, we determine the time delay between inducer addition and fluorescence onset of a GFP reporter. Through independent characterization of the GFP maturation process, we can separate the lag time caused by the reporter from the intrinsic activation time of the arabinose system. The resulting distribution of intrinsic time delays scales inversely with the external arabinose concentration, and is compatible with a simple stochastic model for arabinose uptake. Our findings support the idea that the heterogeneous timing of gene induction is causally related to a broad distribution of uptake proteins at the time of sugar addition.