Chemotaxis in external fields: Simulations for active magnetic biological matter

Area of Science:

• Microbial motility and biophysics
• Theoretical biology and modeling
• Biomimetic engineering

Background:

• Microswimmer movement is often modeled using active Brownian particle (ABP) models.
• Microorganisms employ stochastic strategies like run-and-tumble or run-and-reverse for chemotaxis.
• External fields (gravity, magnetic fields, fluid flow) can influence microswimmer behavior.

Purpose of the Study:

• To introduce a modified ABP model incorporating internal states for stochastic directional swimming strategies.
• To investigate the impact of external fields on chemotaxis in microorganisms.
• To explore magneto-aerotaxis in magnetotactic bacteria and the interplay between magnetic alignment and active reorientation.

Main Methods:

• Developed a variant of active Brownian particle models with internal states.
• Incorporated mechanisms for directional bias in chemotaxis and interactions with external fields.
• Applied the model to simulate E. coli chemotaxis and magneto-aerotaxis in magnetotactic bacteria.

Main Results:

• Magnetic orientation can improve chemotaxis in magnetotactic bacteria, even with inclined magnetic fields.
• Run-and-tumble motion with a parallel magnetic field maximizes chemotactic velocity.
• Run-and-reverse strategies are more advantageous than run-and-tumble in the presence of magnetic torque, aligning with observed bacterial behavior.

Conclusions:

• The modified ABP model effectively describes complex microbial strategies like chemotaxis under external fields.
• Magnetic fields can provide a significant advantage for bacterial chemotaxis, particularly when combined with reversal mechanisms.
• Findings offer insights for designing future magnetic biohybrid swimmers.