Speaker
Description
Bacteria use quorum sensing (QS), a process based on the production and detection of autoinducers, to coordinate gene expression in response to environmental cues and population density [1]. Although the molecular mechanisms of QS are well understood, its evolutionary role in natural environments remains unclear. In fluctuating conditions, autoinducer signals can become unreliable. Recent theories suggest that bacteria may use QS not only to estimate cell density but also to collectively sense the environment by integrating noisy individual-level signals [2]. Here, we investigate how a QS-regulated genetic toggle switch enables bacterial populations to commit to one of two mutually exclusive phenotypes. At the single-cell level, the system exhibits bistability in gene expression, allowing individual cells to adopt one of two stable states. At the population level, this bistability supports adaptive switching through evolutionary changes in phenotypic traits. Under alternating selection pressures, populations evolve to favor the phenotype most suited to the current environment. When selection pressures are symmetric, stochastic symmetry breaking leads to spontaneous commitment to one phenotype per simulation, despite identical initial conditions. However, environmental noise can disrupt this commitment, resulting in mixed phenotypic states. Our findings support the hypothesis that QS facilitates collective environmental sensing and demonstrate how feedback loops and stochasticity drive population-level adaptation in uncertain environments.
[1] M. B. Miller, B. L. Bassler, Annu. Rev. Microbiol. 2001, 55, 165–199.
[2] S. Atkinson, P. Williams, Trends Microbiol. 2002, 10, 206–211.
