Comparison of the transient responses of Escherichia coli to a glucose pulse of various intensities

tDynamic stimulus-responses of Escherichia coli
DPD2085, yciG::LuxCDABE reporter strain, to glucose
pulses of different intensities (0.08, 0.4 and 1 gL
−1) were compared using glucose-limited chemostat cultures at dilution rate close to 0.15 h
−1. After at least five residence times,
the steady-state cultures were disturbed by a pulse of glucose, engendering conditions of glucose excess with concomitant oxygen limitation. In all conditions, glucose
consumption, acetate and formate accumulations followed
a linear relationship with time. The resulting specific uptake
and production rates as well as respiratory rates were rapidly
increased within the first seconds, which revealed a high
ability of E. coli strain to modulate its metabolism to a new
environment. For transition from glucose-excess to glucoselimited conditions, the cells rapidly re-established its
pseudo-steady state. The dynamics of transient responses
at the macroscopic viewpoint were shown to be independent
on the glucose pulse intensity in the tested range. On the
contrary, the E. coli biosensor yciG::luxCDABE revealed a
transcriptional induction of yciG gene promoter depending
on the quantities of the glucose added, through in situ and
online monitoring of the bioluminescence emitted by the
cells. Despite many studies describing the dynamics of the
transient response of E. coli to glucose perturbations, it is
the first time that a direct comparison is reported, using the
same experimental design (strain, medium and experimental
set up), to study the impact of the glucose pulse intensity on
the dynamics of microbial behaviour regarding growth,
respiration and metabolite productions.