Abstract
While navigating their environments, cells encounter many different signals at once. In the face of uncertain conditions, diversifying the sensitivity to different signals across the population can be useful. Previous studies established that one of the simplest sensory systems, the chemotaxis network of Escherichia coli, can switch between a high diversity bet-hedging strategy, and a low diversity tracking strategy for a ligand as that ligand becomes prevalent. Here, we combine mathematical modeling and single-cell experiments to show that populations of chemotactic bacteria make this transition for each ligand independently. That is, transitioning to tracking one ligand does not compromise the population’s ability to hedge its bets across other future ligands. Remarkably, we found that this independence holds even if those ligands compete for receptor binding sites with the background ligand being tracked. The independence of this transition between two diversity regimes is explained by a simple allosteric model of chemoreceptor clusters with negative integral feedback, which accurately predicts the observed diversity in sensitivity under various background stimulus conditions. Our mathematical analysis shows that similar transitions from bet-hedging to tracking also arise in feed-forward network architectures capable of precise adaptation, suggesting that environment-dependent modulation of diversity may occur in many cell types.
Competing Interest Statement
The authors have declared no competing interest.