Limits of feedback control in bacterial chemotaxis

Area of Science:

• Microbial physiology and behavior
• Systems biology and biophysics
• Chemosensory pathways and signal transduction

Background:

• Organismal navigation relies on integrating sensory input with behavioral responses, creating complex feedback loops.
• Bacterial chemotaxis utilizes zero integral feedback control for robust sensing, but the impact of adaptation rates and behavioral feedback on performance remains unclear.
• Cellular swimming behavior influences the input signals processed by sensory pathways, complicating information transfer during navigation.

Purpose of the Study:

• To investigate how sensory information is utilized by the flagellar motor to optimize chemotactic performance under varying environmental conditions.
• To identify an operational regime that maximizes drift velocity along chemical gradients, considering behavioral feedback and motor adaptation.
• To explore the effects of feedback strength on maintaining optimal performance and the potential benefits of phenotypic diversity.

Main Methods:

• Development of analytical models incorporating experimental data on behavioral feedback and flagellar motor adaptation.
• Utilizing simulations to examine the dynamics of sensory-motor coupling and information transfer.
• Focusing on the response regulator's role in sensory information processing by the motor.

Main Results:

• An optimal operational regime was identified that maximizes drift velocity in chemical gradients, operating outside the motor's typical dynamic range.
• This regime enhances the contrast between run durations up and down gradients, improving navigation efficiency.
• Strong feedback can lead to a non-chemotactic state, necessitating motor adaptation to escape, and suggesting that individual phenotypes may not suffice in all environments.

Conclusions:

• Optimizing sensory-motor coupling is crucial for efficient navigation in diverse chemical environments.
• Phenotypic diversity may be advantageous for populations to collectively maintain optimal chemotactic performance across varying conditions.
• Understanding these operational regimes provides insights into the fundamental principles of biological information processing and adaptation.