Chemotaxis when bacteria remember: drift versus diffusion.

Area of Science:

• Microbiology and Biophysics
• Cellular Biology
• Statistical Mechanics

Background:

• Escherichia coli (E. coli) bacteria navigate environments using chemotaxis, a process involving switching between running and tumbling behaviors.
• Bacterial movement patterns are influenced by past nutrient concentrations, leading to population drift and accumulation in favorable regions.
• Previous models often assumed memory resets at tumbles, which experimental evidence contradicts.

Purpose of the Study:

• To re-examine bacterial chemotaxis without the assumption of memory resets.
• To differentiate the roles of diffusion and directed motion in bacterial navigation based on adaptive responses.
• To introduce a novel coarse-grained model for chemotaxis.

Main Methods:

• Detailed computational simulations of bacterial movement.
• Development and application of various analytical arguments.
• Introduction of a new coarse-grained description of chemotaxis as biased diffusion.

Main Results:

• Non-adaptive bacterial responses result in chemotaxis dominated by diffusion.
• Adaptive bacterial responses lead to chemotaxis dominated by biased motion.
• In adaptive chemotaxis, both population drift and accumulation favor nutrient-rich environments.

Conclusions:

• Adaptive responses are crucial for directed bacterial movement (bias) and effective colonization of favorable regions.
• The study introduces a new 'biased diffusion' model that offers a more accurate description of chemotaxis.
• This work refines our understanding of how bacteria navigate chemical gradients, departing from older, less accurate models.