Abstract
Curli amyloid fibers are major constituent of the extracellular biofilm matrix formed by bacteria of the Enterobacteriaceae family. Within Escherichia coli biofilms, curli gene expression is limited to a subpopulation of bacteria, leading to heterogeneity of extracellular matrix synthesis. Here we show that bimodal activation of curli expression also occurs in well-mixed planktonic cultures of E. coli, resulting in stochastic differentiation into distinct subpopulations of curli-positive and curli-negative cells at the entry into the stationary phase of growth. Monitoring curli activation in individual E. coli cells growing in a microfluidic device revealed that the curli-positive state is only metastable and it can spontaneously revert during continuous growth in a conditioned medium. The regulation by c-di-GMP is not required for curli gene activation or for differentiation of E. coli in subpopulations of curli-producing and curli-negative cells. Instead, we observe that c-di-GMP modulates the probability and dynamics of stochastic curli activation and enhances stability of the curli-positive state.
Competing Interest Statement
The authors have declared no competing interest.
