Figure 1.
Phenotypic heterogeneity in a bacterial population.
(a) Dynamics of heterogeneous population consisting of normal (white) and persister (black) cells: The persisters survive the addition of an antibiotic, and allow the population to grow back after the removal of the antibiotic. (b) Phenotype type switching: Cells stochastically switch between the normal and persister state with rates and
.
Figure 2.
Subpopulations in exponential and stationary phase.
Persister and normal subpopulation growth (with hr
,
hr
,
hr
,
hr
) in an growth medium of carrying capacity
over a long period (50 hours). The inset shows the time evolution of subpopulation ratio (
) from exponentially growth phase to stationary phase. The dashed lines indicate the limits for exponential growth and no growth discussed in the text.
Figure 3.
(a) Numerical integration of Eqs. (1) over a growth period of 15 hours (with hr
,
hr
) followed by a stress period (with
hr
,
hr
) of another 15 hours. The switching rates were chosen to be
hr
and
hr
. The killing curve of total population show two distinct phases, a fast-decaying phase and a slow-decaying phase. (b) Numerical integration of Eqs. (1) over a stress period of 15 hours followed by a regrowth period of another 15 hours. The regrowth curve of the total population shows two distinct phases, a slow-growing phase followed by a fast-growing phase. The parameters are the same as in (a).
Table 1.
Rates for switching between the normal and persister phenotype.
Figure 4.
(a) The average growth rate over an environmental cycle is plotted as a function of the phenotype switching rate () for different environmental durations (
). The figure shows the existence of an optimal switching rate for a given cycle duration
. (b) Existence of an optimal switching rate: Average growth rate as function of the switching rate (
). An optimal switching rate is seen for slowly varying environment, but not if one environmental duration is short. The growth rates are the same as in Fig. 3.